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I was about to calculate the area of some polygons and before I did I did some research. I found that the area of the polygon will be represented in the units of the projection used. So I did some digging to find that the projection I need is BC Albers, but when I went into the list of projections in QGIS, I found that there were two that could the correct ones. The first is EPSG:3005 NAD83 BC ALBERS, and the second one is EPSG:3153 NAD83(CSRS)/BC ALBERS

I have projected the polygon as both and saw no difference in the result. I was looking on http://prj2epsg.org/epsg/3005 and it says:

"This CRS name may sometimes be used as an alias for NAD83(CSRS) / BC Albers. See CRS code 3153"

Just wondering if anyone knows why there are two seemingly identical projections and if there is any difference. Also what does CSRS stand for?

Thanks!

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My guess is that as a NAD you have to determine your location in the NAD projection and that will give you the code you are looking for. Canadian Spatial Reference System, As an Alias it would not matter, same as. –  lewis Mar 18 '13 at 18:38
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A review of this community wiki might be helpful: gis.stackexchange.com/questions/664/… –  mkennedy Mar 18 '13 at 20:06

1 Answer 1

up vote 2 down vote accepted

CSRS stands for the Canadian adoptation of NAD83:

http://www.geod.nrcan.gc.ca/userguide/guideline/guideline4/guideline4a_e.php

In fact, there are several projections with identical definitions. Some of them are intended to reflect tectonic moves, but usually this is not yet implemented in GIS software.

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Cool, thanks for the direction. –  Chewy Mar 18 '13 at 20:07

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