阅读说明：本技术 基于多源卫星测高数据的水位测量及变化监测方法及装置 (Water level measurement and change monitoring method and device based on multi-source satellite height measurement data ) 是由 李国元 唐新明 金建文 陈继溢 张重阳 刘克 万玮 幺嘉棋 禄競 于 2020-12-15 设计创作，主要内容包括：本发明提供了一种基于多源卫星测高数据的水位测量及变化监测方法及装置,该方法包括：获取目标对象的第一卫星测高数据和第二卫星测高数据,第一卫星激光测高数据对应的第一时间序列和第二卫星测高数据对应的第二时间序列存在交叉时间序列；根据交叉时间序列对应的第一卫星测高数据和第二卫星测高数据计算差异修改值；根据第一卫星测高数据、第二卫星测高数据、差异修改值计算目标对象在目标时间序列内的水位信息；根据目标时间序列内的水位信息预测目标对象在预设时间段内的水位。通过实施本发明,即使在单个卫星寿命较短、覆盖能力有限、不同的卫星搭载的测高系统的情况下,也能综合多类卫星数据,实现对长时间序列的水位变化进行研究。(The invention provides a water level measurement and change monitoring method and device based on multi-source satellite height measurement data, wherein the method comprises the following steps: acquiring first satellite height measurement data and second satellite height measurement data of a target object, wherein a first time sequence corresponding to the first satellite laser height measurement data and a second time sequence corresponding to the second satellite height measurement data have cross time sequences; calculating a difference modification value according to the first satellite height measurement data and the second satellite height measurement data corresponding to the cross time sequence; calculating water level information of the target object in the target time sequence according to the first satellite height measurement data, the second satellite height measurement data and the difference modification value; and predicting the water level of the target object in a preset time period according to the water level information in the target time sequence. By implementing the invention, even under the conditions that a single satellite has short service life, limited coverage capability and different satellite-carried height measurement systems, various satellite data can be integrated, and the water level change of a long-time sequence can be researched.)

1. A water level measurement and change monitoring method based on multi-source satellite height measurement data is characterized by comprising the following steps:

acquiring first satellite height measurement data and second satellite height measurement data of a target object, wherein the first satellite height measurement data comprises water level information of the target object in a first time sequence, the second satellite height measurement data comprises water level information of the target object in a second time sequence, and the first time sequence and the second time sequence have a cross time sequence;

calculating a difference modification value between the first satellite altimetry data and the second satellite altimetry data according to the first satellite altimetry data and the second satellite altimetry data corresponding to the cross time sequence;

calculating water level information of the target object in a target time sequence according to the first satellite height measurement data, the second satellite height measurement data and the difference modification value;

and predicting the water level of the target object in a preset time period according to the water level information in the target time sequence.

2. The method for measuring and monitoring the water level based on the multi-source satellite altimetry data according to claim 1, wherein the step of obtaining the first satellite altimetry data and the second satellite altimetry data of the target object comprises:

acquiring first initial satellite height measurement data and second initial satellite height measurement data;

and screening the first initial satellite height measurement data and the second initial satellite height measurement data according to constraint parameters corresponding to the first initial satellite height measurement data and the second initial satellite height measurement data respectively to obtain the first satellite height measurement data and the second satellite height measurement data.

3. The method for water level measurement and change monitoring based on multi-source satellite altimetry data according to claim 1 or 2, wherein after the step of obtaining the first satellite altimetry data and the second satellite altimetry data of the target object, the step of calculating the difference modification value between the first satellite altimetry data and the second satellite altimetry data according to the first satellite altimetry data and the second satellite altimetry data corresponding to the cross time sequence further comprises:

and if the elevation datum of the first satellite elevation data and the elevation datum of the second satellite elevation data are different, correcting the first satellite data and the second satellite data according to a target elevation datum.

4. The method for measuring and monitoring changes in water level based on multi-source satellite altimetry data according to any one of claims 1 to 3, wherein after the step of calculating the water level information of the target object in a target time series according to the first satellite altimetry data, the second satellite altimetry data and the difference modification value, and before the step of predicting the water level of the target object in a preset time period according to the water level information in the target time series, the method further comprises:

and filtering the water level information which does not meet the preset condition in the water level information in the target time sequence by adopting a median absolute deviation method.

5. The method for measuring and monitoring changes in water level based on multi-source satellite altimetry data according to any one of claims 1 to 3, wherein after the step of calculating the water level information of the target object in a target time series according to the first satellite altimetry data, the second satellite altimetry data and the difference modification value, and before the step of predicting the water level of the target object in a preset time period according to the water level information in the target time series, the method further comprises:

acquiring area information of the target object in the target time sequence;

and acquiring missing water level information in the target time sequence according to a preset water level-area relation model and the area information of the target object in the target time sequence, wherein the preset water level-area relation model is established according to the corresponding relation between the water level information and the area information of the target object in the target time sequence.

6. The method for measuring and monitoring changes in water level based on multi-source satellite altimetry data according to any one of claims 1-5, wherein the step of predicting the water level of the target object within a preset time period according to the water level information in the target time series comprises:

and predicting the water level of the target object in a target time period according to a preset water level prediction model, wherein the preset water level prediction model is established according to the corresponding relation between the water level information in the target time sequence and the time.

7. The method for measuring and monitoring water level change based on multi-source satellite altimetry data according to any one of claims 1-6, wherein after the step of predicting the water level of the target object within a preset time period according to the water level information in the target time series, the method further comprises:

and if the variation of the water level of the target object in the preset time period relative to the water level in the last time period of the preset time period is larger than a preset threshold, executing early warning work.

8. The utility model provides a water level measurement and change monitoring devices based on multisource satellite altimetry data which characterized in that includes:

the height measurement data acquisition module is used for acquiring first satellite height measurement data and second satellite height measurement data of a target object, wherein the first satellite height measurement data comprises water level information of the target object in a first time sequence, the second satellite height measurement data comprises water level information of the target object in a second time sequence, and the first time sequence and the second time sequence have a cross time sequence;

the difference modification value calculation module is used for calculating a difference modification value between the first satellite altimetry data and the second satellite altimetry data according to the first satellite altimetry data and the second satellite altimetry data corresponding to the cross time sequence;

the water level information correction module is used for calculating the water level information of the target object in a target time sequence according to the first satellite height measurement data, the second satellite height measurement data and the difference correction value;

and the water level prediction module is used for predicting the water level of the target object in a preset time period according to the water level information in the target time sequence.

9. A computer device, comprising:

at least one processor; and a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the at least one processor to perform the method of water level measurement and change monitoring based on multi-source satellite altimetry data of any one of claims 1-7.

10. A computer-readable storage medium storing computer instructions for causing a computer to perform the method for water level measurement and change monitoring based on multi-source satellite altimetry data according to any one of claims 1 to 7.

Technical Field

The invention relates to the technical field of satellite monitoring, in particular to a water level measurement and change monitoring method and device based on multi-source satellite height measurement data.

Background

The lake reservoir water level is very sensitive to the response of climate change and human activities, and is an important content for monitoring the dynamic change of the lake. The traditional lake and reservoir water level acquisition mode is realized by a ground hydrological monitoring station, and although the traditional lake and reservoir water level acquisition mode has the advantages of high measurement precision, continuous observation frequency and the like, the problem that the hydrological station cannot be established on a large scale due to regional and cost problems also exists. In recent years, satellite height measurement technology has developed into an important means for monitoring the water level of lakes and reservoirs. Compared with the traditional lake and reservoir water level monitoring method, the method can quickly acquire lake water level information with higher precision and wider range in real time and all weather, can monitor the water level of lakes and reservoirs which are distributed on high mountains, plateaus or remote areas and lack ground water level monitoring stations in near real time, and provides scientific data guarantee for the study of the water level change of the lakes and reservoirs. In order to carry out more comprehensive research on the water level of the lake and the reservoir and even accurately predict the water level of the lake and the reservoir, data of a long-time sequence of the water level of the lake and the reservoir need to be acquired, but the service life of the current satellite is limited, the coverage capacity is limited, the data acquisition of the long sequence of the same lake and the reservoir is difficult to complete through a height measurement system carried on one satellite, the height measurement systems carried on different satellites are different, and the water level information acquired by different height measurement systems cannot be directly applied to the research on the water level change of the same lake and the reservoir. Therefore, the multi-source satellite height measurement data are integrated, the unification of the elevation datum is realized, and the requirement for monitoring and researching the water level change of the long-time sequence of the lake and the reservoir is very necessary.

Disclosure of Invention

Therefore, the technical problem to be solved by the invention is to overcome the defect that the research on the water level change of a long-time sequence is difficult through satellite height measurement data in the prior art, so that a water level measurement and change monitoring method and device based on multi-source satellite height measurement data are provided.

The invention provides a water level measurement and change monitoring method based on multi-source satellite height measurement data, which comprises the following steps: acquiring first satellite height measurement data and second satellite height measurement data of a target object, wherein the first satellite height measurement data comprise water level information of the target object in a first time sequence, the second satellite height measurement data comprise water level information of the target object in a second time sequence, and the first time sequence and the second time sequence have a cross time sequence; calculating a difference modification value between the first satellite altimetry data and the second satellite altimetry data according to the first satellite altimetry data and the second satellite altimetry data corresponding to the cross time sequence; calculating water level information of the target object in the target time sequence according to the first satellite height measurement data, the second satellite height measurement data and the difference modification value; and predicting the water level of the target object in a preset time period according to the water level information in the target time sequence.

Optionally, in the water level measurement and change monitoring method based on multi-source satellite altimetry data provided by the present invention, the step of obtaining first satellite altimetry data and second satellite altimetry data of a target object includes: acquiring first initial satellite height measurement data and second initial satellite height measurement data; and screening the first initial satellite height measurement data and the second initial satellite height measurement data according to constraint parameters corresponding to the first initial satellite height measurement data and the second initial satellite height measurement data respectively to obtain first satellite height measurement data and second satellite height measurement data.

Optionally, in the water level measurement and change monitoring method based on multi-source satellite altimetry data provided by the present invention, after the step of obtaining the first satellite altimetry data and the second satellite altimetry data of the target object, before the step of calculating the difference modification value between the first satellite altimetry data and the second satellite altimetry data according to the first satellite altimetry data and the second satellite altimetry data corresponding to the cross time sequence, the method further includes: and if the elevation datum of the first satellite elevation data and the elevation datum of the second satellite elevation data are different, correcting the first satellite data and the second satellite data according to the target elevation datum.

Optionally, in the method for measuring and monitoring change of water level based on multi-source satellite altimetry data provided by the present invention, after the step of calculating water level information of the target object in the target time series according to the first satellite altimetry data, the second satellite altimetry data, and the difference modification value, before the step of predicting the water level of the target object in the preset time period according to the water level information in the target time series, the method further includes: and filtering the water level information which does not meet the preset condition in the water level information in the target time sequence by adopting a median absolute deviation method.

Optionally, in the method for measuring and monitoring change of water level based on multi-source satellite altimetry data provided by the present invention, after the step of calculating water level information of the target object in the target time series according to the first satellite altimetry data, the second satellite altimetry data, and the difference modification value, before the step of predicting the water level of the target object in the preset time period according to the water level information in the target time series, the method further includes: acquiring area information of a target object in a target time sequence; and acquiring missing water level information in the target time sequence according to a preset water level-area relation model and the area information of the target object in the target time sequence, wherein the preset water level-area relation model is established according to the corresponding relation between the water level information and the area information of the target object in the target time sequence.

Optionally, in the method for measuring water level and monitoring change based on multi-source satellite altimetry data provided by the present invention, the step of predicting the water level of the target object within a preset time period according to the water level information within the target time sequence includes: and predicting the water level of the target object in the target time period according to a preset water level prediction model, wherein the preset water level prediction model is established according to the corresponding relation between the water level information in the target time sequence and the time.

Optionally, in the method for measuring and monitoring change of water level based on multi-source satellite altimetry data provided by the present invention, after the step of predicting the water level of the target object within a preset time period according to the water level information within the target time series, the method further includes: and if the variation of the water level of the target object in the preset time period relative to the water level in the last time period of the preset time period is larger than a preset threshold, executing early warning work.

The invention provides a water level measurement and change monitoring device based on multi-source satellite height measurement data, which comprises: the height measurement data acquisition module is used for acquiring first satellite height measurement data and second satellite height measurement data of a target object, wherein the first satellite height measurement data comprises water level information of the target object in a first time sequence, the second satellite height measurement data comprises water level information of the target object in a second time sequence, and the first time sequence and the second time sequence have a cross time sequence; the difference modification value calculation module is used for calculating a difference modification value between the first satellite altimetry data and the second satellite altimetry data according to the first satellite altimetry data and the second satellite altimetry data corresponding to the cross time sequence; the water level information correction module is used for calculating the water level information of the target object in the target time sequence according to the first satellite height measurement data, the second satellite height measurement data and the difference correction value; and the water level prediction module is used for predicting the water level of the target object in a preset time period according to the water level information in the target time sequence.

A third aspect of the present invention provides a computer apparatus comprising: at least one processor; and a memory communicatively coupled to the at least one processor; the storage stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so as to execute the water level measuring and change monitoring method based on the multi-source satellite altimetry data provided by the first aspect of the invention.

A fourth aspect of the present invention provides a computer-readable storage medium storing computer instructions for causing a computer to execute the method for measuring and monitoring water level based on multi-source satellite altimetry data according to the first aspect of the present invention.

The technical scheme of the invention has the following advantages:

1. the invention provides a water level measurement and change monitoring method based on multi-source satellite height measurement data, which is characterized in that when the water level of a target object is detected, the used data is satellite height measurement data, compared with the data obtained through a hydrological station, the satellite height measurement data used in the method is not limited by regions when being obtained, so that the first satellite height measurement data and the second satellite height measurement data both comprise more complete data of the target object, the time sequences of the first satellite height measurement data and the second satellite height measurement data obtained in the water level measurement and change monitoring method based on the multi-source satellite height measurement data have cross sequences, the difference modification value between the first satellite height measurement data and the second satellite height measurement data can be calculated through the first satellite height measurement data and the second satellite height measurement data corresponding to the cross sequences, and the first satellite height measurement data and the second satellite height measurement data are spliced according to the difference modification value, the water level information of the target object in the long time sequence is obtained, the water level measurement of the target object in the long time sequence is realized, the water level of the target object in a preset time period is accurately predicted according to the water level information in the long time sequence, and the change monitoring of the water level of the target object is realized. Therefore, by implementing the invention, even under the conditions that a single satellite has short service life, limited coverage capability and different satellite-mounted height measuring systems, the data of multiple types of satellites can be integrated, and the research on the water level change of a long-time sequence is realized.

2. According to the water level measurement and change monitoring method based on the multi-source satellite height measurement data, after the first initial satellite height measurement data and the second initial satellite height measurement data are obtained, the first initial satellite height measurement data and the second initial satellite height measurement data are screened according to the constraint parameters corresponding to the first initial satellite height measurement data and the second initial satellite height measurement data, the first initial satellite height measurement data and the second initial satellite height measurement data are screened through the constraint parameters, height measurement data with poor quality can be eliminated, and therefore the water level of a target object can be accurately detected.

3. According to the water level measuring and change monitoring method based on the multisource satellite height measurement data, when missing data exists in water level information in a target time sequence, the water level information is filled through area information in the target time sequence, complete water level information is obtained, and the complete water level information in the target time sequence provides guarantee for accurate prediction of the water level of a target object in a preset time period.

4. The water level measuring and change monitoring device based on the multisource satellite height measurement data provided by the invention has the advantages that when the water level of a target object is detected, the used data is the satellite height measurement data, compared with the data obtained through a hydrological station, the satellite height measurement data used in the invention is not limited by regions when being obtained, so that the first satellite height measurement data and the second satellite height measurement data both comprise more complete data of the target object, the time sequences of the first satellite height measurement data and the second satellite height measurement data obtained in the water level measuring and change monitoring device based on the multisource satellite height measurement data have cross sequences, the difference modification value between the first satellite height measurement data and the second satellite height measurement data can be obtained through calculation through the first satellite height measurement data and the second satellite height measurement data corresponding to the cross sequences, and the first satellite height measurement data and the second satellite height measurement data are spliced according to the difference modification value, the water level information of the target object in the long time sequence is obtained, the water level measurement of the target object in the long time sequence is realized, the water level of the target object in a preset time period is accurately predicted according to the water level information in the long time sequence, and the change monitoring of the water level of the target object is realized. Therefore, by implementing the invention, even under the conditions that a single satellite has short service life, limited coverage capability and different satellite-mounted height measuring systems, the data of multiple types of satellites can be integrated, and the research on the water level change of a long-time sequence is realized.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a flowchart illustrating a method for measuring water level and monitoring changes based on multi-source satellite altimetry data according to an embodiment of the present invention;

FIG. 2a is a footprint image of a water body region of a high-resolution seven-grade satellite laser altimeter in an embodiment of the invention;

FIG. 2b is a diagram of an echo waveform of a high-resolution seven-model satellite laser altimeter in the embodiment of the present invention;

FIG. 3 is a schematic diagram illustrating a corresponding relationship between time and water level of Hara lake in 2002-2019 in the embodiment of the present invention;

FIG. 4 is a flowchart illustrating another exemplary method for measuring and monitoring water level based on multi-source satellite altimetry data according to an embodiment of the present invention;

FIG. 5 is a flowchart illustrating another exemplary method for measuring and monitoring water level based on multi-source satellite altimetry data according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of a basic principle of satellite altimetry in an embodiment of the present invention;

FIG. 7 is a flowchart illustrating another exemplary method for measuring and monitoring water level based on multi-source satellite altimetry data according to an embodiment of the present invention;

FIG. 8 is a flowchart illustrating another exemplary method for measuring and monitoring water level based on multi-source satellite altimetry data according to an embodiment of the present invention;

FIG. 9 is a schematic diagram illustrating the corresponding relationship between the area and the water level of the Qinghai lake according to the embodiment of the present invention;

FIG. 10 is a schematic diagram illustrating water level information in a target time series after filling according to a water level-area relationship model in an embodiment of the present invention;

FIG. 11 is a schematic block diagram of a specific example of a water level measuring and change monitoring device based on multi-source satellite altimetry data according to an embodiment of the present invention;

FIG. 12 is a functional block diagram of a computer device in an embodiment of the present invention.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "first", "second", and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The embodiment of the invention provides a water level measurement and change monitoring method based on multi-source satellite height measurement data, as shown in figure 1, comprising the following steps:

step S10: the method comprises the steps of obtaining first satellite height measurement data and second satellite height measurement data of a target object, wherein the first satellite height measurement data comprise water level information of the target object in a first time sequence, the second satellite height measurement data comprise water level information of the target object in a second time sequence, and a cross time sequence exists between the first time sequence and the second time sequence. The target object refers to a reservoir, a lake, a river, or the like. The first satellite laser height measurement data and the second satellite laser height measurement data are obtained by a height measurement system carried by a satellite, the first time sequence is the service time of the satellite for obtaining the first satellite laser height measurement data, and the second time sequence is the service time of the satellite for obtaining the second satellite laser height measurement data.

In a specific embodiment, the first satellite laser height measurement data and the second satellite height measurement data may be satellite radar height measurement data or satellite laser height measurement data, that is, in the embodiment of the present invention, the satellite radar height measurement data and the satellite laser height measurement data may be combined, two different satellite radar height measurement data may be combined, or two different satellite laser height measurement data may be combined.

The satellite laser height measurement data mainly comprises high-precision ICESat/GLAS, ICESat-2/ATLAS, Hi-Bao-seventh satellite laser height measurement data and the like, and mainly refers to a data base for hydrologic Time Series of incoming Waters (DAHITI), wherein:

the ICESat satellite is launched and lifted off in 2003, and runs after 11 months in 2009 by the American national aerospace agency, a laser altimeter is carried, a pulse is emitted to the ground at the frequency of 40Hz, an echo reflected from the ground is recorded, and light spots with the distance of about 175m and the diameter of about 70 m are formed on the ground. ICESat/GLAS data contained data for a total of 15 different products from GLAH01 to GLAH15, with Release 33 being the most recent version of the data. The global elevation data of the GLAH14 is adopted, and the global elevation data comprises parameters such as longitude and latitude, elevation, waveform saturation correction, reflectivity, cloud cover marking and the like of laser spot foot points.

ICESat-2(Ice, Cloud and Land Elevation Satellite-2) carries an advanced terrain Laser Altimeter system ATLAS (advanced Topographic Laser Altimeter System), which was successfully launched on 9, 15.2018. The ICSat-2/ATLAS adopts a micro-pulse, high repetition frequency and multi-beam photon counting technology, and has a great improvement on the coverage capability and the measurement accuracy compared with the ICESat/GLAS. ATL13 is ATLAS's Global inland Water surface elevation data product, and determines footprint points intersecting the water by using lake boundary vector data HydroLAKES mask and global lake wetland data set. The ATL13 data can observe the area more than 0.01km in the global range²The quantity of water body elements such as lakes, reservoirs, rivers with the length of more than 100m and the like is about 150 to 200 ten thousand.

The high-resolution seven-grade laser is successfully emitted in 2019, 11, 3 and the first laser altimeter with full waveform recording and sampling functions in China is configured. The high-resolution seven-grade satellite laser altimeter points to the vertical rail plane in the direction similar to the nadir point, forms an included angle of 0.7 degrees with the left side and the right side of the nadir point to form 2 wave beams, and has a distance of about 2.4km along the axial point. The absolute pointing measurement precision of the prior high-resolution seven-grade satellite laser altimeter is about 2.5', the slope of the high-resolution seven-grade satellite laser altimeter can be approximately regarded as 0 degree when a calm lake reservoir without wind indicates, and at the moment, when the side sway angle is 1 degree, the elevation error is about 0.106 m; when the yaw angle is 2 degrees, the elevation error is about 0.212 m. When the lateral swing angle is small (for example, limited to within 0.5 °), the method can be used for measuring and monitoring the water level of a lake reservoir with a length in the north-south direction greater than 7.5km by 10cm level, as shown in fig. 2a, a footprint image of a water body area of a high-resolution seven-model satellite laser altimeter in an embodiment is shown, and as shown in fig. 2b, an echo waveform of the high-resolution seven-model satellite laser altimeter in the embodiment is shown.

DAHITI is an inland hydrological time series database constructed by the German geological institute starting in 2013. By far, the data set provides a water level time series of 2799 lakes, reservoirs, rivers and wetlands in the world, wherein 44 lakes, reservoirs and rivers in China have the data set. The DAHITI data set is obtained by multisource altimetry satellite data based on outlier rejection and an extended Kalman filtering algorithm, and the multisource altimetry satellite data comprises radar altimetry data such as Envisat, Cryosat-2, Sentinel-3, SARAL/Altika, Jason-1, Jason-2 and Jason-3. The data set unifies different height measurement satellite data to the same reference ellipsoid, and simultaneously eliminates system elevation errors of different height measurement satellites caused by different instruments, equipment, operation orbits, revisit periods and the like.

Step S20: and calculating a difference modification value between the first satellite altimetry data and the second satellite altimetry data according to the first satellite altimetry data and the second satellite altimetry data corresponding to the cross time sequence.

In a specific embodiment, if the first satellite altimetry data and the second satellite altimetry data are data obtained by a satellite through different measurement systems, the two sets of data have differences and cannot be directly combined to obtain data of a long-time sequence, a difference modification value between the two sets of data needs to be calculated first, and then the two sets of data are subjected to unified modification based on the difference modification value.

Illustratively, in an embodiment of the present invention, the difference modification value is calculated by: acquiring a first water level value H of first satellite height measurement data at a certain moment in a cross time sequence₁And a second water level value H in the second satellite height measurement data at the same time₂Determining a difference between the first water level value and the second water level value as a difference modification value: Δ H ═ H₁-H₂。

Step S30: calculating water level information of the target object in the target time sequence according to the first satellite altimetry data, the second satellite altimetry data and the difference modification value:

H＝H_i+ΔH，

h is the water level value of the target object at a certain time in the target time sequence, H_iIs the value in the first satellite altimetry data or the value in the second satellite altimetry data at the same time as H.

Step S40: and predicting the water level of the target object in a preset time period according to the water level information in the target time sequence.

In an optional embodiment, when the water level of the target object is predicted within a preset time period, the prediction may be performed according to a preset water level prediction model, and the preset water level prediction model is established according to a corresponding relationship between water level information and time within the target time sequence.

For example, a regression model of time and water level may be established by using a least square method according to water level information in a target time sequence, so as to obtain a change trend of the water level of the target object, as shown in fig. 3, which is a corresponding relationship diagram of time and water level of the hara lake between 2002 and 2019, and the water level change trend obtained according to the corresponding relationship diagram of time and water level shown in fig. 3 is: and y is 0.16657x +4077.0869, wherein y represents water level and x represents time.

The water level measurement and change monitoring method based on the multi-source satellite height measurement data provided by the embodiment of the invention has the advantages that when the water level of a target object is detected, the used data is the satellite height measurement data, compared with the data obtained through a hydrological station, the satellite height measurement data used in the method is not limited by regions when being obtained, so that the first satellite height measurement data and the second satellite height measurement data both comprise more complete data of the target object, the time sequences of the first satellite height measurement data and the second satellite height measurement data obtained in the water level measurement and change monitoring method based on the multi-source satellite height measurement data provided by the invention have a cross sequence, the difference modification value between the first satellite height measurement data and the second satellite height measurement data can be obtained through calculation according to the first satellite height measurement data and the second satellite height measurement data corresponding to the cross sequence, and the first satellite height measurement data and the second satellite height measurement data are spliced according to the difference modification value, the water level information of the target object in the long time sequence is obtained, and the water level measurement of the target object in the long time sequence is realized. Therefore, by implementing the embodiment of the invention, even under the conditions that a single satellite has short service life, limited coverage capability and different satellite-mounted height measurement systems, various satellite data can be integrated, and the water level change of a long-time sequence can be researched.

In an optional embodiment, in the water level measurement and change monitoring method based on multi-source satellite height measurement data according to the embodiment of the present invention, as shown in fig. 4, the step S10 specifically includes:

step S11: first initial satellite altimetry data and second initial satellite altimetry data are obtained.

The first initial satellite height measurement data and the second initial satellite height measurement data are first satellite height measurement data and second satellite height measurement data which are not subjected to screening processing respectively.

Step S12: and screening the first initial satellite height measurement data and the second initial satellite height measurement data according to constraint parameters corresponding to the first initial satellite height measurement data and the second initial satellite height measurement data respectively to obtain first satellite height measurement data and second satellite height measurement data.

In a specific embodiment, for different satellite altimetry data, corresponding constraint parameters are also different, specifically, for the ATLAS data, the constraint parameters include a background photon existence degree flag qf _ bckgrd, an electromagnetic bias quality flag qf _ bias _ em, a height deviation fitting quality flag qf _ bias _ fit, and a cloud control flag layer _ flag _ atl09, and the screening for the ATLAS data specifically includes:

judging whether the ATLAS data meets the following conditions:

the background photon existence degree mark is more than or equal to 0 and less than or equal to 6 in qf _ bckgrd;

the electromagnetic bias quality mark-3 is more than or equal to qf _ bias _ em < 4;

the height deviation fitting quality flag-3 is more than or equal to qf _ bias _ fit < 4;

the value of the cloud amount control flag layer _ flag _ atl09 is equal to 0 or 1;

deleting data which does not meet any condition in the ATLAS data;

and after deleting the data which do not meet any condition in the ATLAS data, correcting the ATL13 water level value of the laser point of the effective lake by using an ATL13 First Photon Bias correction identifier (FPB).

For the laser height measurement data of the high-resolution seven-model satellite, the constraint parameters comprise echo peak number, echo pulse width, echo waveform saturation, cloud cover on a footprint image and the number of points falling on the water surface of a target object, and the screening of the laser height measurement data of the high-resolution seven-model satellite specifically comprises the following steps:

judging whether the laser height measurement data of the high-resolution seven-model satellite meets the following conditions:

the number of echo peaks is equal to 1;

the pulse width of the echo is less than or equal to the transmitting pulse width +0.5 ns;

whether the echo waveform is not saturated and the signal-to-noise ratio SNR of the waveform is greater than 15;

whether there is no cloud on the footprint image (i.e., whether the amount of cloud is 0);

whether at least 3 points fall on the water surface of the same target object;

and deleting data which do not meet any condition in the laser height measurement data of the high-grade seven satellite.

According to the water level measurement and change monitoring method based on the multi-source satellite height measurement data, after the first initial satellite height measurement data and the second initial satellite height measurement data are obtained, the first initial satellite height measurement data and the second initial satellite height measurement data are screened according to the constraint parameters corresponding to the first initial satellite height measurement data and the second initial satellite height measurement data, the first initial satellite height measurement data and the second initial satellite height measurement data are screened through the constraint parameters, height measurement data with poor quality can be removed, and therefore the accurate detection of the water level of a target object can be guaranteed.

In an optional embodiment, in the method for measuring and monitoring water level variation based on multi-source satellite altimetry data according to the embodiment of the present invention, as shown in fig. 5, after the step S10 and before the step S20, the method further includes:

step S51: and judging whether the elevation references of the first satellite elevation data and the second satellite elevation data are different, if so, executing the step S52, and if so, executing the step S20.

Step S52: and correcting the first satellite data and the second satellite data according to the target elevation datum.

In a specific embodiment, as shown in fig. 6, the basic principle of satellite height measurement is to measure the time difference between a downward sending pulse and a receiving pulse by a laser height indicator or a radar altimeter carried on a satellite, and calculate the instantaneous distance from the centroid of the satellite to the ground of a satellite, wherein the specific calculation formula is as follows:

H_ortho＝h_Alt-h_Ran-h_Geoid-(Δ_iono+Δ_dry+Δ_wet+Δ_set+Δ_pol)，

wherein h is_RanThe distance from the center of mass of the satellite to the ground; c is the speed of light; Δ t is the time difference between the transmitted pulse and the received pulse; h_orthoIs the lake water level is high; h is_AltIs the ellipsoidal height of the altimeter; h is_GeoidFor the ground levelElevation of the surface relative to a reference ellipsoid; delta_ionoAn ionospheric correction term; delta_dryA dry tropospheric correction term; delta_wetCorrecting terms for wet tropospheric; delta_setA solid tide correction term; delta_polIs an extreme tide correction term.

Because different height measurement satellite products have certain inter-satellite system deviation, and some elevation references are not uniform, for example, the elevation reference of the DAHITI height measurement data is EIGEN-6C4, and the elevation reference of the ICESat-2/ATL13 height measurement data is EGM 2008. In order to combine different satellite height measurement data to obtain long-time sequence data, system deviation among different height measurement satellites needs to be eliminated, height measurement products are unified to the same elevation datum, and then the data after the same elevation datum are combined.

In the embodiment of the present invention, taking the target elevation reference as the EGM2008 as an example, for the satellite laser height measurement data such as the seventh high score that adopts the ground height of WGS84, the formula for converting the satellite laser height measurement data into the positive height reference by using the EGM2008 model is as follows:

Hortho＝Hg-ξ，

hg is the geodetic height of the laser point under a WGS84 ellipsoid, xi is the geodetic plane correction value calculated by adopting an EGM2008 model, and xi can also be calculated according to other geodetic plane models.

For the ICESat/GLAS product elevation using the TOPEX/Poseidon (T/P) satellite reference ellipsoid, it is converted to the positive elevation reference formula using the EGM2008 model:

Hortho＝Hg-ξ-Δh，

wherein, Δ h is the height difference between two ellipsoids, and Δ h ═ cos² Bda-sin²And Bdb, wherein B is latitude, and da and db are the difference between the major axis and the minor axis of the two reference ellipsoids.

In an optional embodiment, the acquired first satellite altitude data and second satellite altitude data may have data missing, or data missing may be caused in the process of filtering and screening the first satellite altitude data and the second satellite altitude data, so that, in the water level measurement and change monitoring method based on multi-source satellite altitude data provided by the embodiment of the present invention, as shown in fig. 7, after the step S30, before the step S40, the method further includes:

step S60: and filtering the water level information which does not meet the preset condition in the water level information in the target time sequence by adopting a median absolute deviation method.

In a specific embodiment, the median absolute deviation method has strong gross error detection capability, and can effectively identify the lake water level elevation abnormal value, and the calculation method of the gross error detection is shown as the following formula:

MAD＝1.4826M(|a₁-M(a₁,...,a_n)|,...,|a_n-M(a₁,...,a_n)|)

H_outlier＜M(a₁,...,a_n)-3·MAD or H_outlier＞M(a₁,...,a_n)+3·MAD，

in the formula, a₁,...,a_nIs in an along-rail elevation sequence; m is the median elevation sequence; h_outlierIs the coarse difference in elevation.

In the embodiment of the invention, the rough elevation difference value along the rail is removed by adopting Median Absolute Deviation (MAD), so that the effective laser elevation points along the rail can be obtained, and the average value of the effective laser elevation points along the rail is calculated to be used as the water level value along the rail.

In an optional embodiment, in the method for measuring and monitoring water level variation based on multi-source satellite altimetry data according to the embodiment of the present invention, as shown in fig. 8, after the step S30 and before the step S40, the method further includes:

step S71: and acquiring the area information of the target object in the target time sequence.

In the embodiment, for the optical satellite image, a large inland lake-reservoir boundary data set (such as Hydrolake) is used to roughly locate the corresponding lake-reservoir position and boundary, and a buffer area of 2-5km is established. The Normalized Difference Water Index (NDWI) (normalized Difference Water index) is adopted, a single-band ratio is carried out by utilizing a green band (0.52-0.60 mu m) and a near infrared band (0.76-0.96 mu m), and the green band in which the high reflectivity of the Water body is positioned and the near infrared band in which the low reflectivity is positioned are taken as the ratio according to the principle, so that the area of the Water body is highlighted. The normalized water body index calculation formula is as follows:

in the formula: rGreen is a green band and rNIR is a near infrared band.

And when the NDWI is greater than 0, the corresponding pixel is a suspected water body, frequency histogram statistics is carried out on the water body object and the pixels of the buffer area, threshold segmentation is carried out by utilizing a double-peak histogram, the water body boundary is further determined, and therefore the area information of the target object is calculated according to the water body boundary.

Step S72: and acquiring missing water level information in the target time sequence according to a preset water level-area relation model and the area information of the target object in the target time sequence, wherein the preset water level-area relation model is established according to the corresponding relation between the water level information and the area information of the target object in the target time sequence.

In a specific embodiment, after the area information of the target object in different periods is obtained, the water level information in the same period as the area information is obtained, and then a water level-area relation model is established according to the area information and the water level information of the target object in each period. As shown in fig. 9, which is a corresponding relationship between the area of the Qinghai lake and the water level, when the water level-area relationship model is established, a polynomial model can be established according to the water level information and the area information:

h＝a₁s+a₂s²+a₃s³+...+b，

wherein h is the water level value and s is the area value.

In a specific embodiment, a first order polynomial, that is, a · s + b linear mode h may be directly used, and the model established as shown in fig. 9 is y 0.0084554x + 3158.4658.

After obtaining the water level-area relationship model, the water level information in the time period in which the water level information is missing may be supplemented according to the area information in the time period, so as to obtain complete water level information, in a specific embodiment, the water level information in the target time series after being filled according to the water level-area relationship model is as shown in fig. 10.

In an optional embodiment, after the water level of the target object in the preset time period is obtained in step S40, if the variation of the prediction result in the previous time period relative to the preset time period is greater than a preset threshold, the early warning operation is performed, where the value of the preset threshold may be determined according to the latest satellite laser height measurement data, for example, the preset threshold may be set to 0.5m, and if the variation of the measurement result in the previous time period relative to the preset time period is greater than 0.5m, the early warning operation is performed.

According to the water level measuring and change monitoring method based on the multi-source satellite height measurement data, provided by the embodiment of the invention, the water level of a target object in a preset time period can be predicted according to the water level information in a target time sequence, and when the variation of a prediction result relative to the water level in the last time period is larger than a preset threshold value, early warning work is executed, so that the target object can be protected in time by implementing the method.

An embodiment of the present invention further provides a water level measurement and change monitoring device based on multi-source satellite height measurement data, as shown in fig. 11, including:

the height measurement data obtaining module 10 is configured to obtain first satellite height measurement data and second satellite height measurement data of a target object, where the first satellite height measurement data includes water level information of the target object in a first time sequence, the second satellite height measurement data includes water level information of the target object in a second time sequence, and the first time sequence and the second time sequence have a cross time sequence, and details are described in the above embodiment with reference to the description of step S10, and are not described herein again.

The difference modification value calculation module 20 is configured to calculate a difference modification value between the first satellite altimetry data and the second satellite altimetry data according to the first satellite altimetry data and the second satellite altimetry data corresponding to the cross time sequence, for details, refer to the description of step S20 in the foregoing embodiment, and details are not described herein again.

The water level information correction module 30 is configured to calculate water level information of the target object in the target time sequence according to the first satellite altimetry data, the second satellite altimetry data, and the difference modification value, for details, refer to the description of step S30 in the foregoing embodiment, and details are not described here again.

The water level predicting module 40 is configured to predict the water level of the target object within the preset time period according to the water level information in the target time sequence, for details, refer to the description of step S40 in the foregoing embodiment, and no further description is given here.

The water level measuring and change monitoring device based on the multi-source satellite height measurement data provided by the embodiment of the invention has the advantages that when the water level of a target object is detected, the used data is the satellite height measurement data, compared with the data obtained through a hydrological station, the satellite height measurement data used in the invention is not limited by regions when being obtained, so that the first satellite height measurement data and the second satellite height measurement data both comprise more complete data of the target object, the time sequences of the first satellite height measurement data and the second satellite height measurement data obtained in the water level measuring and change monitoring device based on the multi-source satellite height measurement data provided by the invention have a cross sequence, the difference modification value between the first satellite height measurement data and the second satellite height measurement data can be obtained through calculation according to the first satellite height measurement data and the second satellite height measurement data corresponding to the cross sequence, and the first satellite height measurement data and the second satellite height measurement data are spliced according to the difference modification value, the water level information of the target object in the long time sequence is obtained, and the water level measurement of the target object in the long time sequence is realized. Therefore, by implementing the invention, even under the conditions that a single satellite has short service life, limited coverage capability and different satellite-mounted height measuring systems, the data of multiple types of satellites can be integrated, and the research on the water level change of a long-time sequence is realized.

An embodiment of the present invention further provides a computer device, as shown in fig. 12, the computer device mainly includes one or more processors 51 and a memory 52, and fig. 12 takes one processor 51 as an example.

The computer device may further include: an input device 53 and an output device 54.

The processor 51, the memory 52, the input device 53 and the output device 54 may be connected by a bus or other means, and the bus connection is exemplified in fig. 12.

The processor 51 may be a Central Processing Unit (CPU). The Processor 51 may also be other general purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) or other Programmable logic devices, discrete Gate or transistor logic devices, discrete hardware components, or combinations thereof. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The memory 52 may include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function; the storage data area may store data created from use of the water level measurement and change monitoring device based on the multi-source satellite altimetry data, and the like. Further, the memory 52 may include high speed random access memory, and may also include non-transitory memory, such as at least one magnetic disk storage device, flash memory device, or other non-transitory solid state storage device. In some embodiments, memory 52 optionally includes memory remotely located from processor 51, and these remote memories may be connected via a network to a water level measurement and change monitoring device based on multi-source satellite altimetry data. The input device 53 may receive user input of a calculation request (or other numerical or character information) and generate key signal inputs associated with the water level measurement and change monitoring device based on the multi-source satellite altimetry data. The output device 54 may include a display device such as a display screen for outputting the calculation result.

The embodiment of the invention also provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer instructions, and the computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions can execute the water level measurement and change monitoring method based on the multi-source satellite height measurement data in any method embodiment. The storage medium may be a magnetic Disk, an optical Disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a Flash Memory (Flash Memory), a Hard Disk (Hard Disk Drive, abbreviated as HDD) or a Solid State Drive (SSD), etc.; the storage medium may also comprise a combination of memories of the kind described above.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.