I just came across something that is very disturbing.
I imported a batch of points from a CSV file.
2 points have the same geographic location (they are a single archaeological site occupied at different time periods)
I import them into a UTM Zone 30 European Datum 1950 location and they are georeferenced using the following values:
x coordinate = -31415 and y coordinate = 4116150
Once they are in GRASS, however, they show up in 2 different places on my map. I captured the coordinates from the screen and did a query on both points and the results agree. Here are the reported locations of the 2 points
East = -31418.8180586, North = 4116177.13863
East = -30639.9940711, North = 4116551.27956
The coordinates are significantly different from each AND from the imported coordinates of the 2 points. It looks like one of the points is place close to (but not exactly) on the original north coordinate and the other points is placed close to (but not exactly) on the original east coordinate.
What is going on here???
Michael
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Arizona State University
voice: 480-965-6262 (SHESC), 480-727-9746 (CSDC)
fax: 480-965-7671 (SHESC), 480-727-0709 (CSDC)
www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu
On Sat, Jun 8, 2013 at 8:55 PM, Michael Barton <Michael.Barton@asu.edu> wrote:
I just came across something that is very disturbing.
I imported a batch of points from a CSV file.
2 points have the same geographic location (they are a single archaeological
site occupied at different time periods)
I import them into a UTM Zone 30 European Datum 1950 location and they are
georeferenced using the following values:
x coordinate = -31415 and y coordinate = 4116150
Once they are in GRASS, however, they show up in 2 different places on my
map. I captured the coordinates from the screen and did a query on both
points and the results agree. Here are the reported locations of the 2
points
East = -31418.8180586, North = 4116177.13863
East = -30639.9940711, North = 4116551.27956
The coordinates are significantly different from each AND from the imported
coordinates of the 2 points. It looks like one of the points is place close
to (but not exactly) on the original north coordinate and the other points
is placed close to (but not exactly) on the original east coordinate.
What is going on here???
Can you provide CSV file with the 2 points and the exact commands you
used? A simple import should not change the coordinates.
Markus M
Here is the command:
v.in.ascii --overwrite input=/Users/cmbarton/sites_out/sites_out.csv output=sites_test separator=, skip=1 x=15 y=16 cat=0
Here is the projection
g.proj -p
-PROJ_INFO-------------------------------------------------
name : Universal Transverse Mercator
proj : utm
zone : 30
no_defs : defined
datum : eur50
ellps : international
towgs84 : -131,-100.3,-163.4,-1.244,-0.020,-1.144,9.39
-PROJ_UNITS------------------------------------------------
unit : Meter
units : Meters
meters : 1
Here is the csv file:
Once imported, take a look at the sites in the lower left. You can see the pairs of sites that should be the same location.
Michael
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Arizona State University
voice: 480-965-6262 (SHESC), 480-727-9746 (CSDC)
fax: 480-965-7671 (SHESC), 480-727-0709 (CSDC)
www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu
On Jun 8, 2013, at 12:37 PM, Markus Metz markus.metz.giswork@gmail.com
wrote:
On Sat, Jun 8, 2013 at 8:55 PM, Michael Barton Michael.Barton@asu.edu wrote:
I just came across something that is very disturbing.
I imported a batch of points from a CSV file.
2 points have the same geographic location (they are a single archaeological
site occupied at different time periods)
I import them into a UTM Zone 30 European Datum 1950 location and they are
georeferenced using the following values:
x coordinate = -31415 and y coordinate = 4116150
Once they are in GRASS, however, they show up in 2 different places on my
map. I captured the coordinates from the screen and did a query on both
points and the results agree. Here are the reported locations of the 2
points
East = -31418.8180586, North = 4116177.13863
East = -30639.9940711, North = 4116551.27956
The coordinates are significantly different from each AND from the imported
coordinates of the 2 points. It looks like one of the points is place close
to (but not exactly) on the original north coordinate and the other points
is placed close to (but not exactly) on the original east coordinate.
What is going on here???
Can you provide CSV file with the 2 points and the exact commands you
used? A simple import should not change the coordinates.
Markus M
(attachments)
sites_out.csv (11.8 KB)