[GRASS-user] Identifying Projection/Datum From Coordinates

[Bryan Keith]

Rich,

I've done this many times, and you really just have to guess.  It
helps to know what units your coordinates are in to narrow down your
choices.  Often you can figure that out if you have a general idea of
how far away a couple of your points are.  Then you guess it has to be
feet or meters.

Well, I just tried the 5 obvious choices (UTM NAD27 and NAD83; NV
stateplane east NAD27 and NAD83 and NAD83 with us-ft).  Here are the
results, and none looks right.  You can see that 32007 (NV stateplane
east NAD27) at least gets you in Nevada but not where you describe.

>cs2cs -f %0.6f +init=epsg:3421 +to +init=epsg:4326
371801.76 427253.14
-116.548880     -36.339992 0.000000

>cs2cs -f %0.6f +init=epsg:32007 +to +init=epsg:4326
371801.76 427253.14
-116.017176     35.923115 0.000000

>cs2cs -f %0.6f +init=epsg:32107 +to +init=epsg:4326
371801.76 427253.14
-113.731151     -33.652406 0.000000

>cs2cs -f %0.6f +init=epsg:26911 +to +init=epsg:4326
371801.76 427253.14
-118.154615     3.864647 0.000000

>cs2cs -f %0.6f +init=epsg:26711 +to +init=epsg:4326
371801.76 427253.14
-118.154603     3.864893 0.000000

Since 32007 was somewhat reasonable, I tried 32008 (central):

>cs2cs -f %0.6f +init=epsg:32008 +to +init=epsg:4326
371801.76 427253.14
-117.100541     35.923099 0.000000

Good luck.  Sorry it wasn't more conclusive.

Bryan

On Fri, May 20, 2011 at 09:38, Rich Shepard <rshepard at appl-ecosys.com> wrote:
>  I'd appreciate advice from folks here on a question of coordinates and
> projections.
>
>  I have been given a list of site coordinates such as these:
> easting: 371801.756688, northing: 427253.142826 located in northeastern
> Nevada. Because they are each 6 digits (left of the decimal point) I assume
> that they are in State Plane Coordinates for eastern Nevada (zone 4601) and
> I want to convert them to UTM (zone 11).
>
>  Using the NGS/NOAA SPC to GeoCoords converter results in latitudes of
> either 50 degrees N (for NAD83 in meters) or 47.5 degrees N (for NAD27 in
> feet), both of which are well off. I live about 45.5 degrees N and am well
> north of the area of interest.
>
>  Please suggest how I can identify the projection and datum for these
> points so I can use proj4 to re-project them.
>
> TIA,
>
> Rich
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