[GRASSLIST:2200] Re: Another problem with r.proj

[Rich Shepard]

On Sat, 28 Jul 2001, Eric G. Miller wrote:

> > 	PROJ_UNITS:
> > unit: unknown
> > units: unknowns
> > meter: 1
>
> Does it help if you change the PROJ_UNITS to?
>
> unit: meter
> units: meters
> meter: 1.0

Eric,

  I didn't pick this up until I sent the response. I just changed it and,
no, it makes no difference.

> Also, it looks like you need to specify the input "mapset" for the
> location (i.e. "spc").

  Tried that, too. I posted to the list as well as to Len when he suggested
this.

> Actually, the datum transformation needs to be done via geodetic
> coordinates following the inverse projection from UTM.  Unfortunately,
> the projection routines in GRASS don't do this at the present.

  Would it be a Good Thing at this point for me to use r.out.ascii and
v.out.ascii on these data sets and then use the USGS 'proj' program? I don't
know if that does datum convertions as well as projection conversions.

> It may or may not be easier to use i.rectify to transform the DEM --
> provided you can find suitable control coordinates. (hint: select 6 or 8
> points spread across the input source; transform them to geodetic
> coordinates; use m.datum.shift to get the corresponding datum shifted
> geodetic coordinates; project the coordinates to your target projection;
> voila, you have control points in both coordinate systems).

  I can't see this as being easier. :-)

  So, does it look like a bug in r.proj to you?

Thanks,

Rich

Dr. Richard B. Shepard, President

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