[CF-metadata] proposed UTM projection

From: Jonathan Gregory <j.m.gregory>
Date: Wed, 2 Feb 2005 08:16:08 +0000

Dear John

Thanks. This looks useful. I've had a look at the geotiff notes and I don't
find them very clear, so I think we need a bit more explanation.

> * UTM_Zone_Number - in range [1,60] (north) or [-1, -60] (south)
I suggest lower case (the software should be case-insensitive anyway, as in
CF standard 2.6). What does this parameter mean? In particular,
> The central meridian and
> false_northing parameters are specified by the UTM zone.
how is this done? Can we give the formulae? Otherwise the specification may be
incomplete.

> false easting parameters (50000 m)
That should be 500000 m i.e. 500 km.

> The ellipsoid parameters /semimajor_axis/ and /inverse_flattening /are
> optional. If not present, the standard ellipsoid for the given UTM zone
> should be used.
What are these default values? I think we need to say how they are chosen.

Since it has these extra parameters, it appears that the UTM projection is not
just a special case of TM. I am not sure that the formulae in the geotiff page
actually say what to do with these numbers, do they? They are hard to follow.
Do you think there is enough information there for an implementation of UTM?

best wishes

Jonathan
Received on Wed Feb 02 2005 - 01:16:08 GMT