How to customize a projection (eg. Austrian Grid MGI 31)?

[Balazs Hober]

Question

We are the German distributor of Magellan GIS products. We sold a MobileMapper6 with DigiTerra software to a German customer.
The German customer (is on CC) wants to use that device in Austria.

The user choose Austrian Grid MGI 31 and imported a DXF file. The dxf file with the coordinates are exact as they were checked with a High end GPS surveying system. On the Digiterra Software the GPS position is several hundred meters away from the drawing.

We checked the parameters and saw that you are using different ones as the surveying world. The parameter form a surveying solution are:
Dx 586 Dy 89 dz 468 rx 5.1 ry 1.4 rz5.4 and a scale of +1.1

Answer
Look at the following flash tutorial to learn how to change and customize the selected projection in DigiTerra Explorer 5


Please note, that the software will save the customized parameters to the Windows Registry. In case you want to use the modified parameters on different devices please apply the above parameters in the Grid.txt file. You can find the mentioned file in the \BIN path of the SD card (or in the "c:\Program Files\DigiTerra Explorer v5\Grid.txt" path on the Desktop version.).

A "manual" way of editing the appropriate projection in Grid.txt
1. Open Grid.txt in your text editor (eg. Notepad)!
2. Based on the header of the Grid.txt you can edit the necessary parameters in line 2711 (or you can create your own projection in a new line):
HEADER:

Code: Select all

Region   Country   Grid   Datum   Algorithm   FalseEasting   FalseNorthing   LongitudeOfOrigin   LatitudeOfOrigin   GridScale   Angle1   Angle2   SemiMajorAxis   InverseFlattening   DeltaX   DeltaY   DeltaZ   RotX   RotY   RotZ   DatumScale

EDITING:


3. Finally save the file and restart the software.

[plavadinho]

Dear All,

I tried to do the same using a Portuguese projection (Igeo_Military Coordinates):

PROJCS["Lisboa_Hayford_Gauss_IGeoE",GEOGCS["GCS_Datum_Lisboa_Hayford",DATUM["D_Datum_Lisboa_Hayford",SPHEROID["International_1924",6378388.0,297.0]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",200000.0],PARAMETER["False_Northing",300000.0],PARAMETER["Central_Meridian",-8.131906111111112],PARAMETER["Scale_Factor",1.0],PARAMETER["Latitude_Of_Origin",39.66666666666666],UNIT["Meter",1.0]]

I tried this in the Mobile Version of DigiTerra because my maps were not in the place where they suposed to be. When i tried this the software gave me an error message:

Program: dtExp.exe
Exception: 0xC000001D
Adress: 00321730

Then the DigiTerra closes and we need to restart the software.

What i want is to use Portuguese raster images in the Mobile version of DigiTerra because our clients use raster images on the field.

The GPS position (target) is not corresponding with the raster image (our position is many kms from the raster image).

We have the raster image and the correspondent prj file along with the jpx, jpg and tab file.

Can someone give me any clues how can i use this correctly?

Thanks in advance.

[Balazs Hober]

Please attach your modified Grid.txt as a .TXT or as a compressed .RAR or .ZIP. We need to test it!
Thanks!