From Synectics Technical Consulting comes an Online Coordinate Reprojection System; requires installation of the Silverlight 2 platform, available for Windows/Mac/Linux. Single point conversion only, unfortunately. Select the input and output projections by clicking on the “…” button next to each setting (default is OSGB 1936 for input, WGS84 geographic for output), then enter the coordinates in the Source coords box at the left separated by a comma; multiple points can be converted by putting each set on a separate line. Make sure you’ve selected the right coordinate order for the source coordinates and destination coordinates; e.g.. the top setting (Easting,Northing) is typical for Mercator-based projections like OSGB, while the bottom is typical for geographic coordinates (lat/long):
Click on “Transform”, and get the source coords re-projected; the input and output projection parameters will show up in the “Messages” box:
The “Swap” button swaps the input and output projection.
While probably not intended as such, you can also use this as a handy EPSG projection code lookup. Type an EPSG code into the box to the immediate right of “Projection In:” or “Projection Out:” , press the Tab key or click somewhere in the program window, and the projection corresponding to that entered code will show up to the right of it:
If you have a projection and want the EPSG code, click on either of the “…” buttons and scroll through the list of projections; the EPSG code is conveniently listed next to each projection:
HT to Andrew Blake.
Actually, the online coordinate conversion tool can convert multiple points in one go. Just paste multiple coordinate pairs – one per line and press convert.
Hope you find it useful.
Andrew