Converting from local coordinates to coordinates GPS?

Question

i am working with business object tool traying to make a kml file to be imported on google maps. I dont know much about geographic systems, but i begin to understand some basic things.

I have a database which give me a local coordinates i know that because the gps has an appfile which has a grid configured and the database says me that units are meters.

The app file shows this information:

Site Point Pairs: 
 Number Of Points: None
Ellipsoid: 
 Name: (WGS 84)
 Semi Major Axis: 6,378,137.000
 Semi Minor Axis: 6,356,752.314
 Flattening: 1/298.2572215381
 Eccentricity: 
 First: 0.0818191911
 Second: 0.0820944382
Datum Transformation: 
 Name: (WGS 84)
 Method: Molodensky
 Parameters: 
 Direction: WGS84 to Local
 Translation X: 0.000
 Translation Y: 0.000
 Translation Z: 0.000
Geoid Model: 
 Name: Subgrid of MEXICO97 (Mexico) 
 Method: Grid
 Geoid Grid File Name: 
Coordinate System: 
 Name: 12 North
 Group: UTM
Projection: 
 Type: Mercator Transversa
 Parameters: 
 Latitud central: 0°00'00.00000"North
 Longitud central: 111°00'00.00000"West
 Falso norte: 0.000
 Falso este: 500,000.000
 Factor de escala: 0.9996
 AZI Parameters: 
 Azimuth Direction: North Azimuth
 Positive Coordinate Direction: NorthEast
Embedded Data: True
Embedded Geoid Grid Extents
Minimum Latitude: 30°53'60.0000"North
Maximum Latitude: 31°18'0.0000"North
Minimum Longitude: 247°03'60.0000"East
Maximum Longitude: 247°33'60.0000"East
CSIB Version: 10.50
CSIB Format: Big Endian

the database shows me this kind of values

vehicle x y z
VE-28 328279 3457947 -48 
VE-28 328295 3459609 192 
VE-28 328288 3459617 193 
VE-28 328304 3459622 192 
VE-28 328220 3457362 -112 

I would like to convert this unit into gps information through some formula. or get the gps to give the gps coordinate to the database instead of the local coordinate.

• BradHards: Its called coordinate transformation or projection. gdal.org/gdaltransform.html is one tool. spatialreference.org/ref/epsg/26912 is UTM12. 4326 is WGS84 (standard GPS output).
• nickves: Check your database, if your database is spatially enabled there's a good change that already provides a build-in function for transforming coordinated from one system to another.

Answer 1

Best method to visualize your data is the free software Quantum GIS. You can add your data with Layer -> Add delimited text. Select space as delimiter; x and y will be automatically selected.

From the information you gave, the projection is WGS84 UTM 12N, EPSG:32612.

You can add Google satellite background with the openlayers plugin to see if the points are on the right spot.

Then you can rightclick on the point layer -> Save as, select keyhole markup language (KML) as format, select a new filename, and EPSG:4326 as CRS for the kml.

You can check to add the kml to the canvas, and the new points should fall on the same place as the first ones.

• Miguel: Thanks Andre, sorry for being late, I have a list with local coordinates in meter, if posible with this software to plot this local coordinates? how can i start i just downloaded this tool. Thanks in advanced
• Miguel: Andre, i have a list of local coordinates based in a base station, where do i put the information of coordinates of the base station, the local coordinates that i have are relatives to that base station, does this work for me even with this condition?
• AndreJ: If you have the coordinates of the base station, use an excel sheet to calculate the sum of coo1(base) + coo2(relative to base). Then export as delimited text and add it as a new layer.
• Miguel: Thanks Andre, i got wrong the idea about coordinates are relatives to base station, it is only used for enhance the accuracy, the coordinates the database gives me are about the grid, thanks for your time your solution, software you suggested worked for me, thanks again. See you Andre, this site really rocks becouse of people like you.

Answer 2

It seems that you want to have longitude and latitude (i.e. WGS84 coordinate system) instead of the projection used in your system. The key is to identify your source SRID (http://en.wikipedia.org/wiki/SRID) and your target SRID (i.e. 4326). If your database is postgis, check the ST_Transform(geometry,SRID) function.

• Miguel: Thanks Fabrice Marchal the database is oracle but i am not allowed to manipulate it, i have to do something out of it. I am goint to ask.