The purpose of choosing projections is to make the nature of the selected projection, and is suitable for the map of the map, while considering that the map is small in the layout range and is uniformly distributed. The map used in the sea is multi-use manifold, because it can maintain the correct position of the azimuth.
China's basic scale topographic map (1: 5,000, 1: 10,000, 1: 25,000, 1: 50,000, 1: 10,000, 1: 250,000, 1: 500,000, 1: 1 million), greater than Equal to 500,000, Gauss-Kruger, is a striped cross-cut elliptical projection, also called transverse mercator; less than 500,000 topographic maps are used, etc. The angle positive axial macating garden cone projection, is a lambert conformal conic; a topographic map of less than 500,000 is multi-use and other angular positive axis cylindrical projection, and the Mercator is called. A map projection system consistent with my country's basic proportional topographic map series should generally be used. The map coordinate system is determined by the geodetic side and map projection, and the geodetic side is approximated using a particular ellipsoid on a particular region of Earth surface, so each country or region has its own geodetic side, and we usually call the Beijing 54 coordinate system. The Xi'an 80 coordinate system actually refers to the two geodes of my country. In the first Soviet Union, my country has established my country's Beijing 54 coordinate system from 1953. In 1978, I use the IAG 75 Ellipsoid recommended by the International Earth Measurement Association. - Xi'an 80 coordinate system, the result of the current GPS positioning belongs to the WGS84 coordinate system, the WGS84 reference surface adopts WGS84 ellipsoid, which is a coordinate system in the center of the ellipsoid. Therefore, there is a difference in the coordinates of their latitude and longitude relative to the same geographic location. The three ellipsoid parameters used (derived from the GB / T 18314-2001 "GB / T 18314-2001"
Ellipsoid
Half-axis
Short half shaft
Krassovsky
6378245
6356863.0188
IAG 75
6378140
6356755.2882
WGS 84
6378137
6356752.3142
The relationship between the ellipsoid and the geodetic side is a pair of relationships, that is, the reference surface is based on the ellipsoid, but the ellipsoid cannot represent the reference surface, the same ellipsoid can define different reference faces, such as Former Pulkovo 1942 of the Soviet Union, the Afgoye reference papers in Africa Somalia have adopted Krassovsky ellipsoid, but their land reference faces are obviously different. In the current GIS commercial software, the geodial reference faces are defined by the conversion of the local reference face to the WGS84, that is, three translation parameters Δx, ΔY, Δz represent the translation value of the two situats; three rotation parameters εx, εy, εz indicates that the local coordinate system is rotated in parallel to the central coordinate system, respectively, respectively, respectively, respectively, respectively, respectively, respectively, the proportional correction factor, for adjusting the ellipsoid size. Beijing 54, Xi'an 80 relative to the conversion parameters of WGS84 have not been open, and the actual work can be used in Beijing 54 or Xi'an 80 coordinate control points to carry out the conversion of WGS84 coordinate values in the work area. Only one known control point is Under (ever), the difference between Beijing 54 and WGS84 coordinates is used as a translation parameter, when the work area is not large, such as Qingdao, the accuracy is also enough. Take (32 °, 121 °) Gaussian-Krig projection results as an example, Beijing 54 and WGS84 reference face, the projection results of the two are about 63 meters in the north-south direction (see below), for dozens or millions of millions Map of this error is not enough, but it should be considered in the engineering map.
Enter coordinate (degree)
Beijing 54 Gauss Projection (Mi) WGS84 Gauss Projection (Mi)
Latitude value (x)
32
3543664
3543601
Sleek value (Y)
121
21310994
21310997
Gauss Kruger Projection
(1) Gaussian - Kluger projection nature
Gauss-Kruger projected a referred to as "Gauss Projection", also known "Isometrics", Earth ellipsoid and flat-faceted projection. German mathematician, physicist, astronomer Gauss (1777 1855) was developed in the 1920s, after the German earth surveyed Johannes Kruger, 1857 ~ 1928) in 1912 The projection formula is added, so the name. The projection is projected in a straight line and the length constant and the equatorial projection is a straight line, which determines the form of a function of Gaussi Lügue projection formula. After projection, in addition to the center of the middard and equator, other meridies are symmetrical in the curve of the central meridian. It is envisaged with an elliptical column to cross the central mid-sm on the ellipsoid surface. According to the above projection conditions, the ellipsoid surfaces of the central sidewhere must be formed in the ellipsoid surface on both sides of the middle. The elliptical cylinder is cut along the bus bar throughout the South Pole, which is the Gaussian projection plane. Take the projection of the central meridian and the equator intersection, the projection of the central meridian is a longitudinal width X-axis, the projection of the equator is the abscissa Y-axis, which constitutes the Gaussk Lüg plane right angle coordinate system.
Gauss - Krogger is very variant in length and area, and the central wire is not deformed. From the center of the circular, the deformation is gradually increased, and the deformation is maximized on the second end of the projection zone. Since its projection is high, it is small, and the calculation is simple (each of the projected belt coordinates, as long as one belt is calculated, the other belts can be applied), so it can be applied in a large-scale topographic map to meet the needs of the military. It can perform precise measurement calculations on the graph.
(2) Gauss - Krir projection zone
The earth ellipsoid is divided into several projection belts according to certain differences, which is the most effective way to limit the length deformation in Gaussian projection. When strip, the length deformation is controlled to make it no greater than the map error, but also makes the column countless to reduce the change calculation, according to this principle, the earth ellipsoid side is divided into the parallel melon zone. To bring a projection. It is usually divided into six degrees or three degrees by 6 degrees or 3 degrees. The six-degree belt from 0 degrees from the day from the west to the east, and the zone is selected as the first, 2 ... 60 belt. The three-degree belt is divided on the basis of the six-degree belt. Its central midway is coincided with the central meridian of the six-degree belt, and the divided strap is coincident, that is, from 1.5 degrees, every separation of 3 degrees from the west to the east, with The number is compiled as a three-degree belt 1, 2 ... 120 belt. my country's long-term range from 73 ° east to 135 °, can be divided into eleventh with six degrees, each with central warp line is 75 °, 81 °, 87 °, ..., 117 °, 123 °, 129 °, 135 °, or twenty-two. The six-degree belt can be used for medium and small scales (such as 1: 250000) map, and the three-degree belt can be used for large proportion (such as 1: 10000) map, the city construction is multi-three Gaussian bounce.
(3) Gaussian - Kluger projection coordinates
Gauss-Kluger is projected by the band method, so each belt is composed of independent systems. Taking the central warp line is projected as longitudinal axis (X), the equator is projected as a horizontal axis (Y), the two axis intersection is the coordinate origin of each belt. The ordinate is calculated by the equator, and the equator is north as the north, and the south is negative. my country is located in the northern hemisphere, and the ordinate is positive. If the horizontal line is zero, the central warp is east, and the west is negative, the absolute value of the horizontal coordinates, the inconvenience is used, so it means that the coordinate longitudinal axis is 500 kilometers as the starting axis, all in the belt The horizontal coordinate value is 500 kilometers. Because the coordinates of the Gaussian Kruger projection each projection belt is the relative value of the original coordinate original, the coordinates of each belt are exactly the same. In order to distinguish where a coordinate system belongs to, add the number before the horizontal axis coordinates For example, (4231898m, 21655933m), wherein 21 is a band number. (4) Gaussian - Krgger projection and UTM projection
Some foreign software such as ARC / INFO or foreign instruments, such as multi-beam data processing software, etc., often does not support Gaussian-Krd, but support UTM projections, therefore often treats UTM projection coordinates as Gaussian - The phenomenon of submitting the coordinates of Kluger.
UTM projection is known as "universal horizontal plum cartoography", is the angular horizontal shaft cutting cylindrical projection (Gaussian-Kluger is an angular horizontal shaft projection), and the cylinder cuts the earth from 80 degrees in the South, 84 degrees north latitude Two contours of two areas, which divides the earth into 60 projection belts, each with a difference of 6 degrees, has been mathematically as a topographic basis. UTM projection and Gaussian projection The main difference between the South-North network cable is maintained in the Central warping of the Gaussian - Krgger projection, that is, the proportional coefficient is 1, and the proportional coefficient of UTM is 0.9996. The UTM projection along each North-South network line proportional coefficient is constant, the direction of the things is variable, the proportional coefficient of the center network cable is 0.9996, and the center point is approximately 363 kilometers from the edge of the widest part of the north and south, the proportional coefficient is 1.00158 .
Gauss - Krgger projection and UTM projection can be approximately XUTM = 0.9996 * x Gauss, YUTM = 0.9996 * Y Gaussian coordinate conversion. The following example (the reference surface is WGS84):
Enter coordinate (degree)
Gauss Projection (Mi)
UTM projection (m)
XUTM = 0.9996 * x Gauss, YUTM = 0.9996 * Y G G G G
Latitude value (x)
32
3543600.9
3542183.5
3543600.9 * 0.9996 ≈ 3542183.5
Sleek value (Y)
121
21310996.8
311072.4
(310996.8-500000) * 0.9996 500000 ≈ 311072.4
Note: The coordinate point (32, 121) is located in the branch of the Gaussian project, the first two "21" in the Gaussian Projection Y value 21310996.8 is the number; the coordinate point (32, 121) is located in the UTM projection 51 band, the UTM projection Y value in the table Did not bring a zone. Due to the mount of the coordinate shaft, the Y value must be subtracted from 500,000 to the proportional factor and then add 500000 when the conversion is transferred. Returns 5. Single point conversion single point conversion steps are as follows: (1) Select whether Gaussian forward conversion or reverse transformation, default to the latitude and longitude to Gaussian projection coordinates, projected coordinate units are rice. (2) Select the geodetic side, default Beijing 54, if it is GPS positioning data, don't forget to switch to WGS84. (3) Select the band, 3 degrees or 6 degrees, default is 6 degrees. (4) Enter the central tape (114 ° E ~ 120 ° e) central height of 117 degrees, 21 (120 ° E ~ 126 ° E) central height of 123 degrees. (5) If a forward projection, select the latitude and longitude input data format, there are three options, default to decurity format. The specific input method is as follows: format
Original latitude value
Original longitude value
Input latitude value
Enter longitude value
Decimal system
35.445901 °
122.997344 °
35.445901
122.997344
Degree
35 ° 26.7541 '
122 ° 59.8406 '
3526.7541
12259.8406
Degree
35 ° 26'45.245 "
122 ° 59'50.438 "
352645.245
1225950.438
(6) Positive projection According to the selected format, enter the latitude and longitude value in the "input" field, and the anti-projection input is based on the x, y coordinate value of the meter unit. (7) Click the Single Conversion button. (8) View the calculation result in the "Output" column. Returns 6. Batch conversion batch conversion steps are as follows: (1) Prepare input data files that need to be converted, require a text file, divided into two columns, first column latitude or longitudinal coordinate values, second columns or lateral coordinate values The two columns are separated from spaces. When projected, the latitude value and the longitude value format may have three options (see table), the default is treated as a decimal system; when reverse projection, the longitudinal and lateral coordinate values must be in meters. Below is an example of, hour (the WGS84) of 6 ° with the orthographic projection of the input data file testdata.txt 352645.245 1225950.438 353800.402 1230000.378 351600.519 1225959.506 345800.101 1225959.8 343600.336 1230000.26 341400.018 1225959.897 335159.17 1225959.46 333000.08 1230000.28 (2) is a Gaussian positive selection or conversion inverse conversion, The default is the latitude and longitude to the Gaussian projection coordinates, the projection coordinate unit is rice. (3) Select the geodetic side, default Beijing 54, if it is GPS positioning data, don't forget to switch to WGS84. (4) Select the band, 3 degrees or 6 degrees, default is 6 degrees. (5) Enter the central tape (114 ° E ~ 120 ° E) central height of 117 degrees, 21 tape (120 ° E to 126 ° E) in the center of 123 degrees. (6) If positive projection, select the latitude and longitude input data format in the input data file, there are three options to default to the decimal format. (7) Click the "Batch Conversion" button. The Open File dialog box will enter your data file name. (8) Enter the conversion result file name, click "Save", the program starts to calculate. (9) Open the output file to view the calculation result, the result is divided into five columns, the first sequence number, the second column input latitude value or the longitudinal coordinate value, the third column input longitude value or the lateral coordinate value, the fourth column conversion latitude value or portrait Coordinate values, fifth columns are converted to the manid value or the lateral coordinate value.
