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I'm very new to GRASS.

I've imported some government files (from http://listdata.thelist.tas.gov.au/opendata/) that are available in ESRI and MapInfo format and they display successfully, and show coordinates in GDA94 / MGA zone 55, as expected.

I've also imported a CSV file with points in decimal degrees long and lat using:

v.in.ascii input="stops.txt" output=metro_stops format=point separator=comma skip=1 x=6 y=5 z=0 --overwrite

and I've imported a kmz file from Google Earth.

The points from the CSV file and the kmz file display with coordinates in decimal degrees, so they don't appear anywhere near the ESRI data.

I realize my problem is to do with telling GRASS the coordinate system of the data, or transforming it somehow, but I don't know where to look.

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GRASS-GIS (unlike other GIS software) will not do "on the fly" transforms of coordinate systems. You must always import data into a GRASS location defined to match the imported data's CRS. So you should:

  • first define a new location for all your WGS84 long/lat data. It's easiest to do this on startup, with the Location wizard
  • Import your csv (and kml) data into that location (v.in ascii, as you did)
  • Switch over to the GDA/MGA zone 55 Location (g.mapset location-<your GDA location> mapset=<your GDA mapset> )
  • Use the v.proj module to project the layers from the WGS84, creating new, projected layers in the GDA/MGA zone location (v.proj input=<your CSV based layer> location=<your WGS84 location> mapset=<your WGS84 mapset> output=<name for the projected layer> )
  • Thanks for the guidance, @Micha. It still took me a little while to get the right coordinate system for the WGS long/lat, but that was just my inexperience. (In the end I use the coordinate system of the kmz file, so 'cheated'.) – Richard A Aug 31 '16 at 0:13
  • Not cheating! That's what the "read location from georeferenced data" is for. – Micha Aug 31 '16 at 10:06
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    Got it :-). Keep with GRASS, The long learning curve is worth the effort. – Micha Sep 1 '16 at 9:46

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