Am 26.07.2015 um 17:13 schrieb James Keener:
If I want to use a PCS to do distance calculations over a large area. For instance, lets say I want to calculate a 650km buffer around Pittsburgh, Pa. The buffer would go outside the state plane for Pittsburgh and outside the UTM zone. I decided to punt and just put everything in UTM Zone 17N and do the calculation that way, but I'm not sure if that is the correct thing to do.
I would suggest to use one of the contiguos US CRS, see http://gis.stackexchange.com/questions/141580/which-projection-is-best-for-mapping-the-contiguous-united-states
http://jimkeener.com/posts/projections if anyone wants to see what I'm talking about or would be kind enough to give me feedback on the post (especially to point out if I'm wrong anywhere in it).
Actually, GCS and PCS are both 3D, becaue you always have a height above ellipoid as well. And you can desribe a place on Earth also with a XYZ coordinate system originating in the Earth's Center like GCS.
PCS can be valid for the whole globe too, think of Miller or Robinson projection: http://gis.stackexchange.com/questions/70411/qgis-display-world-country-shape-files-centered-on-pacific-ocean-using-robinson or even more exotic: http://gis.stackexchange.com/questions/1775/discontinuous-or-interrupted-map-projections
In QGIS can't figure out how to create a buffer not in the native units of the projection the layer is part of.
Since the buffer is drawn on a new layer, you can set the CRS of that layer independent from your source layer. You just have to reproject the buffer center into the new CRS.
HTH, André Joost _______________________________________________ Qgis-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-user
