By selecting this section the coordinate operation will perform a conversion of coordinates using formulas introduced by the user. The constants and accepted functions are presented on the page Supported transformations and conversions - Table no.7: Predefined constants and functions. The functions allocated for introducing the formulas are functions generally used to calculate the projections.
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Examples of how to use this section:
- the calculation of a simple projection not defined in the program;
- coordinates inversion;
- coordinates scaling;
- other conversions.
Accepted characters and functions
In this box there are presented information about the characters and functions that can be used to write the formulas. This box can be minimized or maximized by pushing the button from the top left corner of the box.
Introducing calculation formulas
The coordinates of the source system are marked with x, y, z and those of the destination system with X, Y, Z. The source and destination coordinates can be: geocentric Cartesian coordinates, projected coordinates system or geographic coordinates.
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The correspondence of the coordinates, both at input and at output from the coordinate
operation, for:
- 1st ordinate (x) is X, E or φ;
- 2nd ordinate (y) is Y, N or λ;
- 3rd ordinate (z) is Z, H or h.
Note: When the source coordinates x, y are geographic coordinates (φ, λ) and when they are used in trigonometric functions, then it is necessary to convert the angular values from decimal degrees to radians by using the dtor function. When the destination coordinates X, Y are (φ, λ) and the final result is in radians, then it is necessary to convert the angular values from radians to decimal degrees by using the rtod function.
Domain
Select whether the application of this coordinate operation is made on the 2D or 3D domain.
Forward calculation
Introduce the formulas for forward calculation of the coordinates.
Use the reverse calculation
Check this option if you want to introduce formulas for reverse calculation of the coordinates.