Geo

Do you know how it compares with Proj4?
See http://trac.osgeo.org/proj/

It is not as flexible as PROJ4, but is a LOT easier to use.

Off the top of my head, without checking the Geotrans for Android version:

GEOTRANS supports fewer projections and datums/GeoCRS.

No grid/file-based transformation support except for EGM84/96/2008 geoid models.

Does support 3 and 7 parameter (coordinate frame only) transformations. Doesn't support Molodensky-Badekas. All transformations are to WGS84.

Does support geocentric (3D Cartesian) and local Cartesian systems.

Does support MGRS, USNG, GARS, GEOREF, UTM/UPS.

Does NOT support EPSG:3857 out-of-the-box, and at least the last time I tried, it was difficult (maybe impossible) to set up a custom sphere-based datum.

Doesn't support non-Greenwich prime meridians, IIRC.

As far as I recall, PROJ.4 doesn't support MGRS/USNG, etc.

Melita

GEOTRANS for Android

Now that I've installed and opened the Android app...

Weirdly includes NAD27, NAD83, and WGS84 only (and the associated transformations). A subset of GEOTRANS for Windows/UNIX/Linux projections and "notations".

Geodetic
Lambert conformal conic (1 standard parallel + scale factor or 2 std parallel)
Mercator (std parallel or scale factor)
Polar Stereographic (std parallel or scale factor)
MGRS/USNG
UTM/UPS

Does include some version of EGM2008 geoid model. It's called MSL_EGM2008_15M_BCS_HEIGHT.

Oh yes, GEOTRANS (any version) doesn't support State Plane coordinate system.

Melita

AND, 3.4 has new datums and transformations.

*Rubs hands together in glee*

😀