[GRASS-user] Manually Defining Location

[Bryan Keith]

Rich,

I'm not convinced that's a valid wkt description of the coordinate
system you want.

If I convert that to proj.4, I get

+proj=longlat +ellps=clrk66 +datum=NAD27 +no_defs

which is clearly wrong.

If I use the GRASS location wizard and point it to that wkt, it thinks it is

+proj=longlat
+no_defs
+a=6378206.4
+rf=294.9786982
+towgs84=-22.000,157.000,176.000

which is also clearly wrong.

If I try to manually make a proj.4 string from that wkt, I come up with this:

+proj=tmerc +lat_0=34.75 +lon_0=-115.583333 +k=0.9999
+x_0=152400.3048006096 +y_0=-609601.21920243837 +ellps=clrk66
+datum=NAD27 +units=us-ft +no_defs

Check my numbers there because maybe I did something wrong.  When I
use that proj.4 to convert your coordinates, the results are

cs2cs -f %0.6f +proj=tmerc +lat_0=34.75 +lon_0=-115.583333 +k=0.9999
+x_0=152400.3048006096 +y_0=-609601.21920243837 +ellps=clrk66
+datum=NAD27 +units=us-ft +no_defs +to +init=epsg:4326
371801.76 427253.14
-116.051661     41.414985 0.000000

which is SW of

41.87 N, -115.43 W

but I understand that you think you should be NW of that point....
Don't know if this helps or just adds confusion.

Bryan

On Fri, May 20, 2011 at 15:50, Rich Shepard <rshepard at appl-ecosys.com> wrote:
> On Fri, 20 May 2011, Rich Shepard wrote:
>
>> GEOGCS["GCS_North_American_1927",
>> DATUM["D_North_American_1927",
>> SPHEROID["Clarke_1866",6378206.4,294.9786982]],
>> PRIMEM["Greenwich",0.0],
>> UNIT["Degree",0.0174532925199433]],
>
>  I now understand that the above is angular units. However, the problem
> that the location wizard wants local units in meters for tmerc, nad27 rather
> than US feet remains.
>
> Rich
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