Probably the development of surveying and mapping in China is too fast. First, the 54 coordinate system is unified into the 80 coordinate system, and now it has to be updated to the 2000 coordinate system. From July 1st, 2018, the 2000 National Geodetic Coordinate System will be fully adopted. At that time, the National Surveying and Mapping Geography Information Bureau will stop the surveying and mapping results under the non-2000 national geodetic coordinate system.
Every time the coordinate system is updated, it is accompanied by a huge waste of human and material resources. A mine student working in a geological survey unit said that the geological survey system of his province in the past two years has just forced the unification of the Beijing 54 coordinate system in operation to the Xi'an 80 coordinate system. Everyone is still confused. in. I am afraid that it will bring a lot of trouble and confusion.
Technical Guide for Converting Existing Surveying and Mapping Achievements to 2000 National Geodetic Coordinate System
I. Definition of 2000 National Geodetic Coordinate System
The definition of the national geodetic coordinate system includes the origin of the coordinate system, the orientation of the three coordinate axes, the scale, and the definition of the four basic parameters of the earth ellipsoid. The origin of the 2000 national geodetic coordinate system is the mass center of the whole earth including the ocean and the atmosphere; the Z axis of the 2000 national geodetic coordinate system points from the origin to the direction of the earth reference pole of the epoch 2000.0, and the epoch is given by the International Time Bureau. The fixed epoch is the initial point projection of 1984.0. The time evolution of the orientation guarantees that there is no residual global rotation relative to the earth's crust. The X-axis points from the origin to the intersection of the Greenwich reference meridian and the Earth's equatorial plane (epoch 2000.0), Y-axis and Z. The axis and the X axis constitute a right-hand orthogonal coordinate system. Use the scale in the sense of general relativity. The values ​​of the Earth ellipsoid parameters used in the 2000 National Geodetic Coordinate System are:
Long semi-axis a=6378137m
Flat rate f=1/298.257222101
Gravity constant GM=3.986004418×1014m3s-2
Autorotation angular velocity ω=7.292l15×10-5rad s-1
The tidal-free system is still used after the 2000 national geodetic coordinate system.
Second, point coordinate conversion method
(1) Model selection
Coordinate national and provincial scope of the conversion option converts two-dimensional seven-parameter model; the provincial level and below the three-dimensional coordinate conversion selectable four-parameter model or a flat four-parameter model. For the relationship between the relatively independent plane coordinate system and the 2000 national geodetic coordinate system, a planar four-parameter model or a polynomial regression model can be used. The coordinate transformation model is detailed in the sixth part of this guide.
(2) Coincidence point selection
Coordinate coincidence points can use points with coordinate results in both coordinate systems. However, the final coincidence point needs to calculate the residual coordinates of the coincidence point according to the determined conversion parameters, and determine according to the size of the residual value. If the residual is greater than 3 times, the error is eliminated, and the coordinate conversion parameters are recalculated until the accuracy is satisfied. The number of coincident points used to calculate the conversion parameters is related to the size of the conversion area, but not less than 5.
(three) model parameter calculation
Using the determined coincidence point coordinates, the model parameters are calculated using the least squares method according to the coordinate transformation model.
(4) Accuracy assessment and verification
When using the above model for coordinate conversion, the corresponding accuracy index must be met. The specific accuracy evaluation index and evaluation method can be found in the attached content. The partial coincidence point is selected as the external checkpoint, and the conversion parameter calculation is not involved. The conversion coordinates of these points are calculated by the conversion parameters and compared with the known coordinates for external verification. At least 6 uniformly distributed coincident points should be selected to check the coordinate conversion accuracy.
(5) Area selection for parameter calculation of point coordinate transformation model in database
For database under 1980 Xi'an coordinate system, using a set of model parameters calculated data satisfy national 1: 50000 and 250000 precision scale conversion database; six model parameters and calculated data partition to meet national 1 : Precision requirements for 10,000 scale database conversion. For the conversion of the database in the 1954 Beijing coordinate system, the model parameters of the six partitions calculated by the national data can meet the accuracy requirements of 1:500 and 1:25 million scale database conversion; according to (2°×3°) The partition calculation model parameters can meet the accuracy requirements of 1:10000 scale database conversion.
Third, 1:2.5-1: 250,000 database conversion
(1) A database organized by the national basic scale topographic map framing
The graphic data (DLG, DEM, DRG) organized by the national basic scale topographic map framing is converted according to the following scheme.
1, 1:2.5-1: 100,000 DLG database conversion
(1) 1:2.5-1 in the 1954 Beijing coordinate system: 100,000 DLG database conversion
a. According to the corresponding scale grading, the area is divided, and the coordinate conversion is completed in two steps. First, the ellipsoid transformation is performed, and the coordinate shifting is performed by using the X, Y coordinate translation amount of the corresponding scale frame area;
b. Perform data cutting according to the corresponding scale standard framing profile under the 2000 national geodetic coordinate system, and the data blank area in the area edge map is supplemented by the adjacent frame data;
c. Add the square grid layer under the 2000 national geodetic coordinate system to delete the original square grid data layer;
d. Complete post-processing and database construction work such as profile change, data editing, data edge, topology reconstruction, data warehousing, etc.
e, the frame is changed with the edge: when the right picture (Beijing coordinate system of 1954) is connected to the left picture (2000 national geodetic coordinate system), the ellipsoid and the band change of the right picture are first performed, and the left picture is used in the left zone. The amount of translation is the coordinate shift of the image on the right, and the result of the right image (backup) saved in the left band after the edge is completed. Return to the right picture to cancel the translation amount added by the previous band change, and perform the projection transformation. Finally, after the translation is completed by the translation of the right band itself, the adjacent right image can be connected to the edge;
f. Make changes to the metadata related to the underlying geographic information database metadata.
(2) 1:2.5-1 in the Xi'an coordinate system in 1980: 100,000 DLG database conversion
According to the corresponding scale grading, the region is divided, and the ellipsoid transformation is not considered. The X and Y coordinate translation of the corresponding scale frame area is used to coordinate the translation; then the b~f corresponding to the DLG database conversion in the 1954 Beijing coordinate system is used. The steps are carried out.
2, 1:2.5-1: 100,000 DRG database conversion
The original data is an RGB raster data generated by scanning and correcting the original printed map of 300 to 500 dpi, and there is no edge processing of the elements between the frames.
(1) 1:2.5-1:100,000 DRG database conversion under the Beijing coordinate system in 1954
a. Consider the ellipsoid transformation and the X and Y coordinate translation of the corresponding corner points of the figure, calculate the coordinates of the 1954 Beijing coordinate system framing angle point in the 2000 national geodetic coordinate system, and modify the corresponding data header file. Positioning coordinates
B, overlay 2000 at National Geodetic Coordinate System, new profile data in FIG blank new control land base layer (in the grid square profile and the like) or a data area showing the cut and is not supplemented in the Patterns DRG transactions;
c. Add a new control baseline description clause in the 2000 National Geodetic Coordinate System in the legend;
d. Complete the data layering and maintain the original resolution of the DRG data;
e. Change the relevant content in the metadata, increase the coordinates of the standard coordinates of the 1954 Beijing coordinate system in the coordinates of the 2000 national geodetic coordinate system, and calculate the coordinates of the four corners of the standard framing of the 2000 national geodetic coordinate system.
The converted data is the coordinates of the 2000 national geodetic coordinate system and the 1954 Beijing coordinate system.
(2) 1:2.5-1:100,000 DRG database conversion under the Xi'an coordinate system in 1980
Obtain the X, Y coordinate shift amount of the map corresponding to the scale point of the map, calculate the map positioning coordinates according to the shift amount, and modify the data header file; then follow the 1954 Beijing coordinate system to the 2000 national geodetic coordinate system 1:2.5 -1: The steps b to e of the 100,000 DRG database conversion are performed.
The converted data is the coordinates of the 2000 national geodetic coordinate system and the 1980 Xi'an coordinate system.
3, 1:2.5-1: 100,000 DEM database conversion
The original data is grayscale (256) raster data with a resolution of 25 meters, and the indirect side of the database data is well processed. There are two ways to convert this data: one is to regenerate the DEM according to the DLG related layer data (contour line, elevation point) in the 2000 national geodetic coordinate system (see DEM data production specification), and the other is to perform DEM data. Conversion. The DEM data conversion method is given below.
(1) 1:2.5-1:100,000 DEM database conversion under the Beijing coordinate system in 1954
a. According to the scale corresponding to the frame, add a corresponding scale frame to each adjacent side of the content to be supplemented;
b. Consider the ellipsoid transformation and the X and Y coordinate translation of the corresponding scale frame, and obtain the X and Y coordinate correction values;
c. Perform frame coordinate translation according to the coordinate correction value, and at the same time, determine the starting coordinates with reference pixel resolution for data resampling;
d. According to the new map of the 2000 national geodetic coordinate system and the overlapping pixels, the frame is cut and the positioning coordinates in the data header file are changed;
e. Modify the metadata related items.
(2) 1:2.5-1:100,000 DEM database conversion under the Xi'an coordinate system in 1980
a. According to the corresponding scale, the frame is divided into blocks, and a corresponding scale frame is added to each adjacent side of the content to be supplemented;
b. Perform frame coordinate translation according to the X, Y coordinate translation amount of the corresponding scale frame, and determine the starting coordinates to complete the data resampling with reference to the pixel resolution;
c, d according to the 1954 Beijing coordinate system 1:2.5-1: 100,000 DEM database conversion d, e steps.
4, 1: 250,000 DLG database conversion
(1) converting the coordinate plane shift amount 1:25 web is very warp and weft of the amount of translation or direct access to web map the latitude and longitude corresponding to the shift amount;
(2) According to the warp and latitude shift of 1:25 million, the conversion of 1:250000 latitude and longitude data to the latitude and longitude data of the 2000 national geodetic coordinate system is completed (in 1954, the Beijing coordinate system needs to consider both the ellipsoid change and the translation amount);
(3) According to the corresponding 1:250000 standard framing profile under the 2000 national geodetic coordinate system, the data blanking area in the regional edge map is supplemented by the adjacent frame data;
(4) Data post-processing, including: map change, new grid layer addition, data editing, data edge, topology reconstruction, data storage, etc.
(5) Change the metadata file.
5, 1: 250,000 DEM database conversion
(1) Re-interpolating to generate DEM by using the DLG data layer corresponding to the 2000 national geodetic coordinate system;
(2) Change the metadata file according to the new DEM.
(2) Databases established in other ways
1. Graphic database built by region
The graphic database (DLG, DEM, DRG) established by region (province, region, watershed, etc.) can be divided into layers to complete the conversion, and the conversion scheme of the corresponding scale basic geographic information database is converted and synthesized. 1:100,000-1:250,000 database, converted by block by block according to 1:25 million database conversion scheme, and then integrated and integrated; according to non-Gaussian projection, the original data will be 30'×30' or 15' The ×15′ intersection is used as the coordinate conversion reference point, and the coordinates of these reference points in the 2000 national geodetic coordinate system are calculated, and the geographic information software is used for pattern correction to complete the data conversion.
2, the graphical database established by linear strips
The graphic database established by linear strips (realms, rivers, traffic lines, pipelines, etc.) can be segmented according to the direction, length and length of the strips, and then stitched and synthesized; or through a certain density of objects in the strip Two sets of coordinates are corrected point by point through software. specific method:
Block correction: For the 1:10000 block, it will be corrected block by block according to the 1:10000 data conversion scheme; for the 1:50,000 block, it will be corrected block by block according to the 1:2.5-1:100,000 data conversion scheme. Joint synthesis;
Correction point by point: According to the accuracy of the data, establish a coordinate conversion reference point of a certain density (1:100,100 m grid point, 1:52,000 m2 grid point), calculate the coordinates of these reference points in the new coordinate system, use geography The information software completes the data conversion.
3, according to the graph database created without fixed framing partition
According to the coordinate data, the scale and the frame where the data body is located, the organization of the data, the product type (DLG, DEM, DRG), etc., refer to the conversion scheme of the corresponding scale to implement data conversion. .
4, DOM database conversion
The original data is black and white or color image data acquired by aerospace or aerospace remote sensing. It is continuous grayscale (full color) or RGB (color) raster data. There are many ways to resolve the resolution (mainly including 1:5 topographic map mapping). Aerial images of various resolutions, as well as satellite images of 10 meters, 15 meters, 30 meters for special investigations). Image data conversion can be performed as follows.
For DOM data that has been processed and processed according to database organization, the data conversion method of 1:2.5-1:100,000 DEM can be used, or the 4 points of the effective image edge of each scene image can be calculated under the 2000 national geodetic coordinate system. The way coordinates are repositioned.
For DOM data that has not been processed and processed in a database organization, a data conversion method of 1:2.5-1:100,000 DRG can be used, and no new control basic information is added.
For data with a resolution of 5m-30m, the comprehensive coordinate correction value of 1:250000 corresponding frame should be selected according to the 1:250000 frame area where the data subject is located; for the resolution between 2m and 5m The data needs to be based on the 1:50,000 map area where the data body is located to select the comprehensive coordinate correction value of the 1:50,000 corresponding map; thereby determining the coordinate values ​​corresponding to the number of translation pixels in the X and Y directions (directly 1:250000 or 1:50,000 composite coordinate correction value, or obtained by the number of pixels × pixel resolution). According to the high-resolution image data organized by Gaussian projection and image division (framing), the conversion is performed with reference to the 1:100 DOM conversion technology scheme.
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