[GRASS5] projection-transformation

Helena Mitasova - staff helena at gis.uiuc.edu
Fri Dec 22 20:40:05 EST 2000


Here are my examples (sorry that the shift is not
too visible - it was not my intent to stress it in these images)

http://www2.gis.uiuc.edu:2280/modviz/wake/demrdstr.gif

http://www2.gis.uiuc.edu:2280/modviz/wake/ccsoil30m.gif

DEM and soil data(polygons) seem to fit,
streams and streets - lines are shifted

the data are from

streams are
EXP  1 G:\DATA\AGENCY\CENSUS\TIGER_DATA\TIGER95\NAD83\WATER83\WTR37183.00
soils
G:\DATA\AGENCY\CGIA\SOILSURVEY\NAD83\WAKE\WA83.E00
DEM is
F:\TEMP\DATA\AGENCY\USGS\DEMS\NED\BYCOUNTY\WAKE.E00

there is no projection involved in GRASS or m.in.e00 -
all imported data should be in the same projection and with
the same datum.
So I believe that this is not a GRASS projection problem.

So it seems to be  something in arcinfo export data that GRASS does not
understand correctly - are the coordinates relative and
arcinfo knows that they should be shifted but grass does not?
Or the shift is already in the arcinfo data and nobody has
noticed it - I am getting that checked.

At this point I don't remember whether I had this problem
with shape files (I did a lot of imports for those too - 
thanks to the developers who contributed the tools! it is now
much easier to use arcinfo data) but I can check. I have a few more examples
in several completely different locations - all involve
shift between the raster data (DEM, Land use) and vector
line data (streams) imported from arcinfo and the shift is always 
approximatelly the same.

However I must admit that it may be my problem of importing
data with different datums (although the ifnormation that I am
getting with the data says they are the same) or arcinfo problem.

I will let you know when I find something more concrete about the problem,

Helena

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