Converting coordinates between projection systems

This tool is intented to provide a fast and easy-to-use way for converting coordinates between systems commonly used in France (Lambert, UTM, ...). It can be used by all public but can not replace in accuracy professional tools.
CatCo rejects any responsibilty about the use made from results provided by this online service.

Follow steps below: :

1: Pick a source and target system in the dropdown lists
2: Enter data in the frames to the left, X and Y in 2 separate columns
500 lines maximum. Points after 500 will be ignored.
You can directly copy/paste X Y columns from spreadsheets like Excel or OpenOffice
In this latter case, even if data look disorganized at the screen, the tool takes care of reformating them properly when 'Calculate' button is being clicked on.
3: Click on 'calculate'. Results are displayed in the right frames
4 : Map your points to check if the locations are what you expected. If not you might want to use the extra tool "Retrieve the projection system of your data when you don't know it" at the bottom of the page.
5 : Click on 'Select X or Y target' then Copy/Paste to the software of your choice using the mouse right click.

Remarks:
- The tool will take care either of '. or ',' decimal separator
- For American and British users, beware that decimal separator in outputs is ',' (comma)
- Be careful not to use formated data with 1000's separators like commas or blanks ! The converter will not recognize them
- The accuracy of calculation is about 1E-5 degrees for longitude/latitude and 1 to 2 meters for rectangular coordinates X Y at the latitudes of France mainland , except when the Clarke 1880 to WGS84 ellspoid grid is involved (for instance lambert II to lambert 93) in which case the accuracy is in the decimeter range, ie 6 decimals for geographic projections (degrees) or 1 decimal for other projections (meters)
- The GRS80 ellipsoid used in RGF French projection system is assumed to be equivalent to the WGS84 ellipsoid, almost identical.
- Transformations from ellipsoid Clarke 1880 (Lambert II etendu) to ellipsoid WGS84 (Lambert93) are obtained by translation using the official grid of parameters provided by IGN -the French equivalent of Ordnance Survey in the UK or USGS - as opposed to fixed translation values. This methodology leads to fairly accurate results. Discrepancies with other conversion tools might come from processors's accuracy or double/single precision of numbers as well as approximations used in coding.This grid is valid for a lon/lat window of -5.5 <= lon <= 10. et 41 <= lat <= 52. Outside these limits, the standard average parameters are used.
- Input data is checked in a basic way by the converter. Thanks for verifying that input data have been entered or copied/pasted properly
- For geographic projections in Longitude/Latitude 3 ellipsoids are available : WGS84, ED50 (Hayford 1909) and NTF (Clarke 1880). WGS84 is the current international standard. If you don't know the ellipsoid used for your data, WGS84 is probably your best bet. However there might be an error in the positionning up to 10-3 degrees approximately if you picked the wrong ellipsoid.
- For UTM projection, 2 ellipsoids are available: WGS84 and ED50
- To prevent abusive use or jamming the server, the number of points in input has been limited to 500. In any case GeoFree (CatCo) remains free of deciding to suspend the service or limit its access in case of abusive use