Converting utm to lat long with different datums (data?)

Question

I'm a GIS novice, but have code to convert lat/long to UTM coordinates, and it assumes the WGS84 datum.

I also have a list of different values for the earth's radius, roundness, etc:

    Datum      Equatorial Radius (m)  Polar Radius (m)  Flattening

    WGS84         6,378,137            6,356,752.3142      1/298.257223563
    Airy 1830  6,377,563.4             6,356,256.9         1/299.32

etc...

Is calculating a different projection as simple as substituting these different constants? I can't find anything that supports or refutes this possibility..

Thanks

Answer 1

There are many online tools to perform this conversion, this one for instance. That tool provides this reference which has an excel spreadsheet including the required formulas. In programming terms, you can use GDAL/OGR and PROJ4 to effect the conversion seamlessly using Python, for example. Any GIS software package will also be able to reproject the data for you without the hassle.

To answer your last question, no, changing the constants is not sufficient to do the conversion. You are correct, however, that the way the conversion is done is datum-dependent.