A Method and System for Spatiotemporal Data Analysis of Occultation Data

Abstract

The present invention discloses a method and system for spatio-temporal data analysis of occultation data. The method includes: acquiring the spatio-temporal data of occultation data, where the spatio-temporal data includes: the time when the occultation event occurs, and the geodetic longitude, latitude, and altitude of the occultation tangent point; dividing the Earth's surface into uniform grids in space; according to the spatio-temporal data of the occultation event, projecting and accumulating the occultation events into the corresponding grids in sequence according to the chronological order of their occurrence, to obtain the occultation spatio-temporal data divided by grids; according to the occultation spatio-temporal data divided by grids, calculating the number of occultation events and its spatio-temporal distribution data, where the spatio-temporal distribution data includes: global coverage rate and global uniform coverage index; according to the number of occultations and its spatio-temporal distribution data, drawing a global coverage situation diagram of occultation events and the trend diagrams of the number and coverage rate changing with time, and conducting analysis on the coverage rate, uniformity, and timeliness of occultation events in specific time periods and specific regions.

Description

Technical Field

[0001] The present invention relates to the field of earth atmosphere detection technology and its meteorological and climatic applications, and particularly relates to a method and system for spatio-temporal data analysis of occultation data. Background Art

[0002] Global climate change monitoring and numerical weather forecasting are scientific and technological issues jointly faced by countries around the world. The occultation detection technology has the advantages of high vertical resolution, self-calibration, and long-term stability, and is one of the main atmospheric detection data for climate change monitoring and numerical weather forecasting.

[0003] The improvement of the global navigation satellite system and the development of the earth's low-earth orbit satellite constellation provide richer signal resources for occultation detection, and provide favorable conditions for meeting the requirements of global climate monitoring and numerical weather forecasting for the quantity and spatio-temporal distribution of occultations. The World Meteorological Organization points out that more than 25,000 occultation events evenly distributed globally are required every day to meet the basic requirements of global numerical weather forecasting, and the increase in the number of occultations will effectively improve the accuracy of numerical weather forecasting. Therefore, the occultation detection system is developing towards multi-GNSS system compatibility and low-earth orbit satellite constellations. For example, the commercial aerospace company Spire Global in the United States is implementing the "hundred-satellite constellation" GNSS occultation detection mission.

[0004] The planning of the occultation detection mission of the multi-GNSS system compatible low-earth orbit satellite constellation and the evaluation of the effectiveness of large occultation detection missions should be oriented to the needs of global climate monitoring and numerical weather forecasting. However, the traditional statistical method combining the global distribution scatter plot of occultation events and the histogram of the number of occultations along the longitude and latitude is difficult to quantitatively describe and analyze the global distribution and timeliness of massive occultation data. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the prior art, and proposes a method for spatio-temporal data analysis of occultation data, and also proposes a system for spatio-temporal data analysis of occultation data.

[0006] To achieve the above purpose, the present invention proposes a method for spatio-temporal data analysis of occultation data, and the method includes:

[0007] Step 1) Obtain the spatio-temporal data of the occultation data, and the spatio-temporal data includes: the time when the occultation event occurs and the geodetic longitude, latitude, and altitude of the occultation tangent point;

[0008] Step 2) Divide the earth's surface into uniform grids in space;

[0009] Step 3) According to the spatio-temporal data of the occultation events, project and accumulate the occultation events into the corresponding grids in sequence according to the chronological order of their occurrence, and obtain the occultation spatio-temporal data divided by grids;

[0010] Step 4) Calculate the number of occultation events and their spatio-temporal distribution data based on the occultation spatio-temporal data divided by grids, where the spatio-temporal distribution data includes: global coverage rate and global uniform coverage index;

[0011] Step 5) Draw a graph showing the global coverage of occultation events, as well as the trends of the number and coverage rate changing with time according to the number of occultations and their spatio-temporal distribution data, and conduct an analysis of the coverage rate, uniformity, and timeliness of occultation events in specific time periods and specific regions.

[0012] As an improvement of the above method, step 2) specifically includes: taking the longitude and latitude (0°, 0°) as the reference origin, and dividing the Earth's surface into uniform grids with a size of L×L in space according to the horizontal resolution of occultation atmospheric detection, the scale of the occultation constellation, and the detection requirements, where the unit of L is km.

[0013] As an improvement of the above method, step 3) specifically includes:

[0014] Based on the universal time t when the occultation event occurs ro and the starting universal time t0 of the statistical period, the normalized time t is obtained as:

[0015] t = t ro - t0 (1)

[0016] Based on the geodetic longitude λ of the occultation tangent point ro and latitude project the occultation event into the grid to obtain the column number col and row number row of the grid matrix:

[0017]

[0018] where k is the scale factor, e is the eccentricity of the Earth reference ellipsoid, a is the semi-major axis of the Earth reference ellipsoid, is the reference latitude for scaling;

[0019]

[0020]

[0021] As an improvement of the above method, step 4) specifically includes:

[0022] Based on the occultation spatio-temporal data divided by grids, calculate the ratio of the grid area S visited by the occultation event occ to the sum S of the areas of all grids tot to obtain the global coverage rate GCR of the occultation event as:

[0023] GCR = (S occ / S tot)×100% (5)

[0024] Based on the occultation spatio-temporal data divided by grids, calculate the global uniform coverage index UCI(n) of occultation events according to the following formula:

[0025] UCI(n) = (N ≥n / N tot )×100% (6)

[0026] where n takes the average value of the number of occultation events relative to N tot , N tot represents the total number of grids, and N ≥n represents the number of grids where the number of visits to occultation events is greater than or equal to n.

[0027] As an improvement of the above method, step 5) specifically includes:

[0028] According to the number of occultations, add time and space constraint conditions to formulas (5) and (6), draw the global coverage of occultation events and the trend graphs of their quantity and coverage rate changing with time, and analyze the global coverage rate of occultation events and the global uniform coverage index in specific time periods and specific regions.

[0029] A spatio-temporal data analysis system for occultation data, the system includes: a data acquisition module, an earth surface division module, an occultation event projection module, an occultation event coverage rate and uniformity calculation module, and a data analysis module; where

[0030] The data acquisition module is used to acquire the spatio-temporal data of occultation data, and the spatio-temporal data includes: the time when the occultation event occurs and the geodetic longitude, latitude and height of the occultation tangent point;

[0031] The earth surface division module is used to divide the earth surface into uniform grids in space;

[0032] The occultation event projection module is used to project and accumulate the occultation events into the corresponding grids in sequence according to the spatio-temporal data of the occultation events according to the chronological order of their occurrence, and obtain the occultation spatio-temporal data divided by grids;

[0033] The occultation event coverage rate and uniformity calculation module is used to calculate the number of occultation events and their spatio-temporal distribution data according to the occultation spatio-temporal data divided by grids, and the spatio-temporal distribution data includes: the global coverage rate and the global uniform coverage index;

[0034] The data analysis module is used to draw the global coverage of occultation events and the trend graphs of their quantity and coverage rate changing with time according to the number of occultations and their spatio-temporal distribution data, and perform the analysis of the coverage rate, uniformity and timeliness of occultation events in specific time periods and specific regions.

[0035] As an improvement of the above system, the processing process of the earth surface division module includes: taking the longitude and latitude (0°, 0°) as the reference origin, dividing the earth surface into uniform grids with a size of L×L in space according to the occultation atmospheric detection horizontal resolution, the scale of the occultation constellation, and the detection requirements, where the unit of L is km.

[0036] As an improvement of the above system, the processing process of the occultation event projection module includes:

[0037] Based on the universal time t when the occultation event occurs ro and the starting universal time t0 of the statistical period, the normalized time t is obtained as:

[0038] t = t ro - t0 (1)

[0039] Based on the geodetic longitude λ of the occultation tangent point ro and latitude project the occultation event into the grid to obtain the column number col of the grid matrix and the row number row of the grid matrix:

[0040]

[0041] where k is the scale factor, e is the eccentricity of the earth reference ellipsoid, a is the semi-major axis of the earth reference ellipsoid, is the scale reference latitude;

[0042]

[0043]

[0044] As an improvement of the above system, the processing process of the occultation event coverage rate and uniformity calculation module includes:

[0045] Based on the occultation spatio-temporal data divided by grids, calculate the area S of the grids visited by the occultation event occ and the ratio of the sum S of the areas of all grids tot to obtain the global coverage rate GCR of the occultation event as:

[0046]

[0047] Based on the occultation spatio-temporal data divided by grids, calculate the global uniform coverage index UCI(n) of the occultation event according to the following formula:

[0048] UCI(n) = (N ≥n / N tot ) × 100% (6)

[0049] where n takes the number of occultation events relative to N totThe average value, N tot Indicates the total number of grids, N ≥n Indicates the number of grids where the number of occultation event visits is greater than or equal to n.

[0050] As an improvement to the above system, the processing process of the data analysis module includes:

[0051] According to the number of occultations, adding time and space constraint conditions to formulas (5) and (6), drawing a global coverage map of occultation events and the trend graphs of their quantity and coverage rate changing with time, and analyzing the global coverage rate of occultation events and the global uniform coverage index in specific time periods and specific regions.

[0052] Compared with the prior art, the advantages of the present invention are:

[0053] 1. The present invention first proposes the concepts of global coverage uniformity of occultation events and global uniform coverage index;

[0054] 2. The method of the present invention uses a grid map to statistically count the cumulative number of occultation events, calculates and stores the time series of the total number of occultations and the cumulative number of occultation events in each grid, and can realize the analysis of the coverage rate, uniformity and timeliness of occultation events;

[0055] 3. The method and system of the present invention are conducive to realizing the spatio-temporal distribution statistical analysis and visualization of a large amount of occultation data. Description of the Drawings

[0056] Figure 1 Is the flow chart of the spatio-temporal data analysis method of occultation data in Embodiment 1 of the present invention;

[0057] Figure 2 Is the block diagram of the composition of the spatio-temporal data analysis system of occultation data in Embodiment 2 of the present invention;

[0058] Figure 3 Is the trend of the number of occultations and the change of the coverage rate of occultation data drawn by the method of the present invention;

[0059] Figure 4(a) is a global grid divided into 400×400 (km 2 ) and the global coverage rates of 3, 6, 9, and 12 LEO satellite constellations in the multi-GNSS system compatible mode;

[0060] Figure 4(b) is a global grid divided into 400×400 (km 2 ) and the continuous change curve of the number of occultation events of 3, 6, 9, and 12 LEO satellite constellations with time in the multi-GNSS system compatible mode. Detailed Embodiment

[0061] The present invention is for the design of large-scale occultation detection missions and the evaluation of their effectiveness. It first defines the global coverage uniformity index for occultation events, proposes a spatio-temporal data analysis method and system for occultation data, and realizes the quantitative analysis of the number of occultation events, their global coverage rate, uniformity, and timeliness.

[0062] The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0063] Embodiment 1

[0064] As Figure 1 shown, Embodiment 1 of the present invention provides a spatio-temporal data analysis method for occultation data. Specifically, it includes:

[0065] Obtain the spatio-temporal data of occultation data, where the spatio-temporal data of occultation includes: the time when the occultation event occurs, and the geodetic longitude, latitude, and altitude of the occultation tangent point;

[0066] Divide the Earth's surface into uniform grids in space. Since the position of the occultation event is recorded by longitude and latitude, its atmospheric detection horizontal resolution is about 200 km, and the globe can be divided into grids of L×L (km 2 ), such as grids of 200×200 (km 2 ), or according to the specifications of the occultation constellation and detection requirements, divide the globe into uniform grids of 300×300 (km 2 ), 400×400 (km 2 ), 500×500 (km 2 );

[0067] According to the time and position data of the occultation event, project and accumulate the occultation events into the corresponding grids in the order of their occurrence time, and obtain the spatio-temporal data of occultation divided by grids;

[0068] According to the spatio-temporal data of occultation divided by grids, calculate the time series of the number of occultation events, their global coverage rate, and uniformity;

[0069] According to the number of occultations and their spatio-temporal distribution data, draw a trend chart of the global coverage of occultation events, their number, and coverage rate over time, and conduct analysis on the coverage rate, uniformity, and timeliness of occultation events in specific time periods and specific regions.

[0070] As an improvement of the above method, the spatio-temporal data of occultation includes: the time when the occultation event occurs, and the geodetic longitude, latitude, and altitude of the occultation tangent point;

[0071] As an improvement of the above method, the Earth's surface is spatially divided into uniform grids; specifically, since the positions of occultation events are recorded by longitude and latitude, and its horizontal resolution for atmospheric sounding is about 200 km, the globe can be divided into grids of L×L (km 2 ) such as 200×200 (km 2 ), or according to the specifications of the occultation constellation and the detection requirements, the globe can be divided into uniform grids of 300×300 (km 2 ), 400×400 (km 2 ), 500×500 (km 2 ), or grids of other resolutions;

[0072] As an improvement of the above method, according to the time and position data of occultation events, the occultation events are projected and accumulated into the corresponding grids in sequence according to the chronological order of their occurrence, obtaining the occultation spatio-temporal data divided by grids; specifically,

[0073] Based on the universal time t ro of the occurrence of the occultation event and the starting universal time t0 of the statistical period, the normalized time t is:

[0074] t = t ro - t0 (1)

[0075] Based on the latitude and longitude λ ro of the occultation event position, the occultation event is projected into the grid:

[0076]

[0077] where col is the column number of the grid matrix, k is the scale factor, e is the eccentricity of the Earth reference ellipsoid, a is the semi-major axis of the Earth reference ellipsoid, scale reference latitude;

[0078]

[0079] where row is the row number of the grid matrix,

[0080]

[0081] As an improvement of the above method, according to the occultation spatio-temporal data divided by grids, calculate the time series of the number of occultation events and their global coverage and uniformity; specifically,

[0082] Based on the grid division result of the above occultation data, calculate the ratio of the grid area visited by the occultation event to the total area as the global coverage of the occultation event;

[0083] GCR = (S occ / S tot ) × 100% (5)

[0084] Wherein, GCR is the global coverage rate, S occ is the sum of the grid areas visited by occultation events, and S tot is the sum of all grid areas;

[0085] Based on the grid division result of the above occultation data, calculate the Uniform Coverage Index (UCI) of occultation events;

[0086] UCI(n) = (N ≥n / N tot ) × 100% (6)

[0087] Wherein, N ≥n represents the number of grids where the number of visits of occultation events is greater than or equal to n, and N tot represents the total number of grids. When n takes the average value of the number of occultation events relative to N tot , UCI represents the global coverage uniformity of occultation events; By adding time and space constraint conditions to formulas (5) and (6), the coverage rate and uniformity of occultation events in a specific time period and region can be analyzed.

[0088] As an improvement of the above method, according to the occultation quantity and its spatio-temporal distribution data, draw a global coverage situation diagram of occultation events and the trend diagrams of their quantity and coverage rate changing with time, and conduct analysis on the coverage rate, uniformity and timeliness of occultation events in a specific time period and region, specifically including,

[0089] Based on the grid division of the above occultation data and the cumulative number of occultation events, plot and display the statistical situation of occultation events on a global or regional map with geodetic longitude and latitude coordinates;

[0090] Embodiment 2

[0091] As Figure 2 shown, Embodiment 2 of the present invention provides a spatio-temporal data analysis system for occultation data. It is implemented based on the method of Embodiment 1. This system specifically includes: a data acquisition module, an earth surface division module, an occultation event projection module, an occultation event coverage rate and uniformity calculation module, and a data analysis module; wherein,

[0092] The data acquisition module is used to acquire the spatio-temporal data of occultation data, and the spatio-temporal data includes: the time when the occultation event occurs, and the geodetic longitude, latitude and altitude of the occultation tangent point;

[0093] The earth surface division module is used to divide the earth surface into uniform grids in space;

[0094] Occultation event projection module, which is used to project and accumulate occultation events into corresponding grids in sequence according to the time and space data of occultation events according to the chronological order of their occurrence, so as to obtain occultation time and space data divided by grids;

[0095] Occultation event coverage rate and uniformity calculation module, which is used to calculate the number of occultation events and their time and space distribution data according to the occultation time and space data divided by grids, and the time and space distribution data includes: global coverage rate and global uniform coverage index;

[0096] The data analysis module is used to draw a global coverage situation diagram of occultation events and the trend diagrams of their quantity and coverage rate changing with time according to the number of occultations and their time and space distribution data, and conduct analysis on the coverage rate, uniformity and timeliness of occultation events in specific time periods and specific regions.

[0097] Simulation example

[0098] The globe is divided into grids of 400×400 (km 2 )), and the global coverage rate and timeliness of occultation events of occultation constellations composed of 3, 6, 9 and 12 LEO satellites are simulated and analyzed under the compatible mode of multiple GNSS systems. Figure 3 The upper, middle and lower parts respectively show the global coverage of occultation events of the 12-LEO occultation constellation in 6 hours, 12 hours and 24 hours under the compatible mode of multiple GNSS systems. From Figure 3 It can be seen that the global coverage rate of occultation events gradually increases with time accumulation, and the global coverage rates of occultation events in 6 hours, 12 hours and 24 hours are 90%, 99% and 100% respectively.

[0099] Based on the above time series data of the number of occultations and their global coverage rate, the changing trends of the number of occultations and the coverage rate of occultation data are drawn. As shown in Figure 4.

[0100] Figure 4 shows the continuous change curves of the global coverage rate and the number of occultation events of the constellations of 3, 6, 9 and 12 LEO satellites under the compatible mode of multiple GNSS systems. Figure 4(a) is the global coverage rate; Figure 4(b) is the continuous change curve of the number of occultation events with time.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the embodiments, those of ordinary skill in the art should understand that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for spatio-temporal data analysis of occultation data, the method comprising: Step 1) Obtain the spatio-temporal data of the occultation data, the spatio-temporal data including: the time when the occultation event occurs and the geodetic longitude, latitude and altitude of the occultation tangent point; Step 2) Divide the Earth's surface into uniform grids in space; Step 3) According to the spatio-temporal data of the occultation event, project and accumulate the occultation events into the corresponding grids in the order of their occurrence time, and obtain the occultation spatio-temporal data divided by grids; Step 4) Calculate the number of occultation events and their spatio-temporal distribution data according to the occultation spatio-temporal data divided by grids, the spatio-temporal distribution data including: global coverage rate and global uniform coverage index; Step 5) According to the number of occultation events and their spatio-temporal distribution data, draw a trend graph of the global coverage of occultation events and their number and coverage rate changing with time, and perform analysis on the coverage rate, uniformity and timeliness of occultation events in a specific time period and specific area; The specific content of the said Step 4) includes: Based on the occultation spatio-temporal data divided by grids, calculate the grid area S visited by the occultation event occ and the sum S of the areas of all grids tot The ratio is used to obtain the global coverage rate GCR of the occultation event as follows: GCR=(S occ / S to ) t ×100% (5) Based on the occultation spatio-temporal data divided by grids, calculate the global uniform coverage index UCI(n) of occultation events according to the following formula: UCI(n) = (N ≥n / N tot ) × 100% (6) where n is the average value of the number of occultation events relative to N tot ; N tot represents the total number of grids, and N ≥n represents the number of grids where the access times of occultation events are greater than or equal to n.

2. The method for spatio-temporal data analysis of occultation data according to claim 1, wherein The specific content of the said Step 2) includes: Taking the longitude and latitude (0°, 0°) as the reference origin, divide the Earth's surface into uniform grids with a size of L×L in space according to the occultation atmospheric sounding horizontal resolution, the scale of the occultation constellation and the detection requirements, and the unit of L is km.

3. The method for spatio-temporal data analysis of occultation data according to claim 1, wherein, The specific content of the said Step 3) includes: Based on the universal time t when the occultation event occurs ro and the starting universal time t0 of the statistical period, the normalized time t is obtained as follows: t = t ro -t0 (1) Geodetic longitude λ based on the occultation tangent point ro and latitude Project the occultation event onto the grid to obtain the column number col and row number row of the grid matrix: where k is the scale factor, e is the eccentricity of the Earth reference ellipsoid, and a is the semi-major axis of the Earth reference ellipsoid, is the scale reference latitude; 4. The spatio-temporal data analysis method of occultation data according to claim 1, characterized in that The specific content of the said Step 5) includes: According to the number of occultation events, and adding time and space constraint conditions to formulas (5) and (6), draw a trend graph of the global coverage of occultation events and their number and coverage rate changing with time, and analyze the global coverage rate of occultation events in a specific time period and specific area and the global uniform coverage index of occultation events.

5. A spatio-temporal data analysis system for occultation data, characterized in that, The said system includes: a data acquisition module, an Earth's surface division module, an occultation event projection module, an occultation event coverage rate and uniformity calculation module, and a data analysis module; wherein, The data acquisition module is used to obtain the spatio-temporal data of the occultation data, the spatio-temporal data including: the time when the occultation event occurs and the geodetic longitude, latitude and altitude of the occultation tangent point; The Earth's surface division module is used to divide the Earth's surface into uniform grids in space; The occultation event projection module is used to project and accumulate the occultation events into the corresponding grids in the order of their occurrence time according to the spatio-temporal data of the occultation event, and obtain the occultation spatio-temporal data divided by grids; The occultation event coverage rate and uniformity calculation module is used to calculate the number of occultation events and their spatio-temporal distribution data according to the occultation spatio-temporal data divided by grids, the spatio-temporal distribution data including: global coverage rate and global uniform coverage index; The data analysis module is used to draw a trend graph of the global coverage of occultation events and their number and coverage rate changing with time according to the number of occultation events and their spatio-temporal distribution data, and perform analysis on the coverage rate, uniformity and timeliness of occultation events in a specific time period and specific area; The processing process of the occultation event coverage rate and uniformity calculation module includes: Based on the occultation spatio-temporal data divided by grids, calculate the grid area S visited by the occultation event occ and the sum S of the areas of all grids tot The ratio of which gives the global coverage rate GCR of the occultation event as: GCR=(S occ / S to ) t × 100% (5) Based on the occultation spatio-temporal data divided by grids, the global uniform coverage index UCI(n) of occultation events is calculated according to the following formula: UCI(n) = (N ≥n / N tot ) × 100% (6) where n is the average value of the number of occultation events relative to N tot , N tot represents the total number of grids, and N ≥n represents the number of grids where the access times of occultation events are greater than or equal to n.

6. The occultation data spatio-temporal data analysis system according to claim 5, wherein The processing process of the earth surface division module includes: taking the longitude and latitude (0°, 0°) as the reference origin, dividing the earth surface into uniform grids with the size of L×L in space according to the horizontal resolution of occultation atmospheric sounding, the scale of the occultation constellation and the detection requirements, and the unit of L is km.

7. The occultation data spatio-temporal data analysis system according to claim 5, characterized in that The processing process of the occultation event projection module includes: Based on the universal time t when the occultation event occurs ro and the starting universal time t0 of the statistical period, the normalized time t is obtained as follows: t = t ro -t0 (1) Geodetic longitude λ based on the occultation tangent point ro and latitude Project the occultation event onto a grid to obtain the column number col and row number row of the grid matrix: where k is the scale factor, e is the eccentricity of the Earth reference ellipsoid, and a is the semi-major axis of the Earth reference ellipsoid, is the reference latitude for scaling; 8. The occultation data spatio-temporal data analysis system according to claim 5, characterized in that, The processing process of the data analysis module includes: According to the number of occultations, adding time and space constraint conditions to formulas (5) and (6), drawing the global coverage of occultation events and the trend charts of their quantity and coverage rate changing with time, and analyzing the global coverage rate of occultation events in specific time periods and specific regions and the global uniform coverage index of occultation events.

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