[GRASS-user] Correctly Converting LL to LCC

[Glynn Clements]

Rich Shepard wrote:

> > All of the built-in ellipsoids which can be selected by the +ellps=...
> > option use metres. If you want proj or cs2cs to provide or receive
> > coordinates in units other than those used when specifying the semi-major
> > axis, you need to use the +to_meter=... option to specify the scale
> > factor, e.g. +to_meter=0.3048 if you want units of 0.3048 metres (i.e.
> > feet).
> 
>    This must be where I went off. The metadata tells me that the state uses
> international feet so I need to have that translated to meters, or specify
> in the location definition that the units are international feet.
> 
> > This is determined when you create the location.
> 
>    Your advice, please. Should I use the +to_meter conversion or specify all
> distance units in international feet?

The former. Specifying *all* distance units in feet would require
specifying +a= in feet along with one of +b=, +f=, +rf=, +e= or +es=,
rather than using +ellps=grs80. In turn, this would confuse GRASS,
which assumes that the ellipsoid is specified in metres.

-- 
Glynn Clements <glynn at gclements.plus.com>