[GRASS-user] Identifying Projection/Datum From Coordinates

GRASS GRASS user
1

   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

2

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@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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3

Am 20.05.2011 um 17:38 schrieb Rich Shepard:

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).

Hello I just checked here: http://www.earthpoint.us/StatePlane.aspx
and it seems that the zones for Nevada are 27XX (4601 is Washington)..
..maybe that helps.

/Johannes

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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grass-user mailing list
grass-user@lists.osgeo.org
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4

On Fri, 20 May 2011, Bryan Keith wrote:

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.

Bryan,

   I can give that a try, but ...

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.

   None are close. Jarbridge is 41.87 N, -115.43 W and that would be a bit
southeast of the area of interest.

   Nuts. I've no idea when, where, or how these numbers were generated. But,
this summer I'm sure there will be opportunities to get valid locations with
my little GPS.

Thanks,

Rich

5

On Fri, 20 May 2011, Johannes Radinger wrote:

Hello I just checked here: http://www.earthpoint.us/StatePlane.aspx and it
seems that the zones for Nevada are 27XX (4601 is Washington)..
..maybe that helps.

Johannes,

   From what I found on the Web, the FIPSZONE is 27 and the ADSZONE is 4601.
The example zone on the NGS/NOAA converter page had four digits so I used
the ADSZONE.

Thanks,

Rich

6

On Fri, 20 May 2011, Bryan Keith wrote:

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.

Bryan/Johannes,

   I think I know what they might be; I'll be checking this afternoon and
will post the results later.

   The shapefiles from the project are projected in Transverse Mercator/NAD27
so these might be feet in the tmerc projection rather than in state plane.
I'm importing the maps I have now and will create a sites/points file with
these locations and see if they properly overlap.

   Since some of the data files were corrupted when sent to me I did not look
at them until I received a replacement disk with the missing files. Now I'm
importing them into GRASS and that's why I know the projection of the maps.

Rich