0

I am using QGIS 2.10.1 with some Chicago data (from https://data.cityofchicago.org/browse?tags=gis) and the Google Streets plugin.

My issue is with the CRS's for the Chicago layers and the Google Streets layer. Google Streets is in WGS 84/Pseudo Mercator (EPSG 3857) and the other layers are in a User Defined Coordinate Systems CRS. When I leave them as is, they line up perfectly on top of each other, everything matching where it should be. However, if I change the Chicago data CRS to WGS 84 it moves the vectors to Central Africa respective to the Google Streets layer.

What is the reason for this? And can I still perform meaningful analyses using both the Chicago data and the Google Street layer together with different CRS's?

moman822
  • 1,904
  • 3
  • 19
  • 33

1 Answers1

0

That's because when you open them up, QGIS performs an on-fly transformation to line them up correctly based on what CRS they are on.

So when you change the Chicago data CRS to WGS84 you tell them system that you know that this is the correct CRS. But in your case the chicago data is in NAD_1983_StatePlane_Illinois_East_FIPS_1201_Feet as it appears correctly in the prj file.

So you have to right click your shp and click save as. Then you enter the name of the new shp and you choose what CRS you want the new file to have. THis process transforms the CRS from the current CRS to WGS84.

PS I believe https://gis.stackexchange.com/ is the more suitable place for GIS questions. You'll get more answers there.

Community
  • 1
  • 1
geoSAM
  • 203
  • 2
  • 8
  • Thanks a bunch, that seemed to work. I just had trouble with re-saving one shapefile because it has an attribute with _NULL_ for each value and I cannot do any editing on it (because it is in a different CRS?). – moman822 Oct 07 '15 at 22:41
  • I will also head to the other spot for future GIS questions. Thanks! – moman822 Oct 07 '15 at 22:42
  • Glad it worked. I believe being in a different CRS has nothing to do with your trouble with re-saving the shapefile. Something else should be the problem. Since you found my answer helpful could you please upvote it. I just want to earn the privilige of commenting other questions...Thanks – geoSAM Oct 08 '15 at 04:58
  • I have, something to do with my reputation score here, not sure- I think its just not shown publicly yet. – moman822 Oct 08 '15 at 22:26