As a cutting-edge technology GPS, can be convenient and efficient manner determination of the coordinate points, whether operational or accuracy than the conventional total station and other measuring equipment has obvious advantages. With differential GPS stations all over the country continued to establish and abolish the U.S. SA policy, making stand-alone positioning accuracy is improved greatly, and some have reached the sub-meter accuracy, to meet the national land resources survey, land use change, remote sensing, sea the right to use the application inventory and so on. In general, we use the coordinate system of 1954 or the 1980 Beijing Xi'an coordinate system (hereinafter referred to as 54 lines and 80 lines), while the GPS coordinates of the determination of WGS-84 coordinate system coordinates, the need for coordinate transformation. For non-working staff for the surveying profession's, although the GPS positioning operation is very easy, Dan coordinates Zhuanhuan Ze Nan Yi master, EXCEL is Bijiaopuji's spreadsheet program, can Chuli more complicated math calculation and use it to 进行 GPS coordinate transformation, Mian Ji calculation will be very comfortable and natural. To the coordinate system conversion, can not do without Gauss projection conversion, the following description were carried out using EXCEL GPS coordinates conversion method and conversion method.
1, using EXCEL for Gauss projection conversion
BL conversion from latitude and longitude to the Gaussian plane rectangular coordinates XY (Gauss projection is counted), or converted from the XY BL (Gaussian inverse projection), generally require specialized computer software to complete, in the popular conversion software, there is an common deficiencies is less flexibility, most still require a point to carry out a point, not done in batches, to the actual work and caused much inconvenience. I found that EXCEL can be very intuitive to use, easy to complete the coordinate conversion work does not require the preparation of any software, only the corresponding cell in the EXCEL enter the appropriate formula can be. The following 54 lines as an example, the calculation method.
BL to complete the latitude and longitude coordinates XY plane rectangular conversion, in EXCEL need to occupy approximately 21, of course, the reader can be simplified formula or intuitive to consider the appropriate percentage increase or decrease in the number of columns. In EXCEL, enter the beginning of the formula cell is different, reflected in the different formula to formula on line 2 column 1 (A2 format) as the starting cell, for example, the cell formula is as follows:
Cell
Cell content
Explanation
A2
Enter Central Meridian, to degrees. Minutes form input, such as 115 degrees 30 minutes, enter 115.30
Initial Data L0
B2
= INT (A2) + (INT (A2 * 100)-INT (A2) * 100) / 60 + (A2 * 10000-INT (A2 * 100) * 100) / 3600
Degree into the L0
C2
Degree of latitude in decimal form input values, such as 38 ° 14'20 ", enter 38.1420
Initial Data B
D2
To enter decimal degrees longitude value
Initial data L
E2
= INT (C2) + (INT (C2 * 100)-INT (C2) * 100) / 60 + (C2 * 10000-INT (C2 * 100) * 100) / 3600
The degree of B into
F2
= INT (D2) + (INT (D2 * 100)-INT (D2) * 100) / 60 + (D2 * 10000-INT (D2 * 100) * 100) / 3600
The degree of L into
G2
= F2-B2
L-L0
H2
= G2/57.2957795130823
Transformed into radians
I2
= TAN (RADIANS (E2))
Tan (B)
J2
= COS (RADIANS (E2))
COS (B)
K2
= 0.006738525415 * J2 * J2
L2
= I2 * I2
M2
= 1 + K2
N2
= 6399698.9018/SQRT (M2)
O2
= H2 * H2 * J2 * J2
P2
= I2 * J2
Q2
= P2 * P2
R2
= (32005.78006 + Q2 * (133.92133 + Q2 * 0.7031))
S2
= 6367558.49686 * E2/57.29577951308-P2 * J2 * R2 +(((( L2-58) * L2 +61) *
O2/30 + (4 * K2 +5) * M2-L2) * O2/12 +1) * N2 * I2 * O2 / 2
Results X
T2
=(((( L2-18) * L2-(58 * L2-14) * K2 +5) * O2/20 + M2-L2) * O2 / 6 +1) * N2 * (H2 * J2)
Results Y
Formula table EXCEL software sources and methods of operation, please refer to the information, not repeat them here. According to the formula in the table above, enter into the appropriate cell, the latitude and longitude can be easily obtained from the plane rectangular coordinates. When you enter the latitude and longitude of all, the drop-down with the mouse can get all the calculations. Many of the table cell formulas for the intermediate course, you can use the column hide function of EXCEL is no need to show these hidden columns, formed on the surface of the calculation of standard reports, so that the whole computation is simple. In theory, calculate the amount of data is infinite, when the first enter the formula, the equivalent of their own to complete the establishment of a software can save them for future reuse, once and for all.
Second, GPS coordinates transformation method and area calculation
GPS coordinate system used by the U.S. Department of Defense 1984, the world coordinate system, referred to WGS-84, which is a protocol terrestrial reference system, coordinate origin in the Earth's center of mass. GPS measurements of 54 and China 80 Coordinates department or a difference of tens of meters to more than 100 meters, with regional differences, differences are also different, with crude down to statistics, about 70 meters difference in western China, about 140 meters northeast of the southern 75 meters, 45 meters or so central. Thus, the need to WGS-84 coordinates transformation coordinate system for plotting to use. Coordinate system transformation between the seven parameters commonly used method or three-parameter method, seven parameters for X translation, Y translation, Z Pan, X Rotation, Y Rotation, Z Rotation and scale ratio parameters, if we neglect the rotation parameters and scale ratio parameters was three-parameter method, three-parameter method for the special case of seven-parameter method. Where Z, Y, Z Cartesian coordinate system of space geodetic coordinates, the median for the conversion process. In practice, we used the plane rectangular coordinates, can skip the space Cartesian coordinate system, omit the complex calculations, a simple change it? To this end, the author conducted a long-term practice, proved to be feasible. Its principle is: not measured by the GPS coordinates as the WGS-84 WGS-84 coordinates, but as a systematic error of 54 has a Department of coordinates, then known by the State points to correct and eliminate the system error. The method was temporarily called the coordinate correction method, the following coordinates to WGS-84 coordinate system into 54 as an example, data processing method:
First, select a country near measurement point is known, the known point in the determination with GPS latitude and longitude coordinates WGPS-84 B and L, to this coordinate system as coordinates of the 54 errors, using the latitude and longitude of 54 Department of EXCEL BL into plane rectangular coordinates X'Y ', and then compared with known coordinates of the offset can be calculated:
△ X = X-X '
△ Y = Y-Y '
Type in the X, Y control point for the country known coordinates, X ', Y' for the determination of coordinates, △ X and △ Y is the offset.
Obtain the offset, you can use this offset to correct the other measuring points measured in the region has. GPS measurements of other points of latitude and longitude measurements, converted into a plane coordinate X'Y ', in the XY coordinates directly with offsets have been converted on 54 Coordinates:
X = X '+ △ X
Y = Y '+ △ Y
EXCEL calculation sheet in the last two columns, attached on the correct number and were obtained with the calculated sum of XY, that are converted result. If the measurement line is a closed region, then the results can be ordered up by line, and then enter the appropriate formula can calculate the area of the region. Calculate the coordinates of the area with the principles and formulas, and is not described, the reader may refer to the relevant information. Be noted that the area of precision largely unaffected by the precision of coordinate transformation, if the operator only required area, then converted from time to coordinate this step, just take into XY on the line BL.
On the 1:1 million scale mapping, the County Administrative Region in the context of the general (such as 40Km × 40Km), with this simple correction method to convert the coordinates and the more complex seven-parameter method is not much different. 1:1 million scale change can meet the requirements of the investigation, depending on the accuracy of GPS receiver itself, with little to do with the choice of conversion method. When the area is large, the use of the method may make the error increases, then may consider sub-regional transformation.