I'm trying to get a better grasp of coordinate systems, datums, projections etc. I understand that certain systems preserve different things; distance, shape, angles, area. I'm wondering how you can tell what a certain system is preserving. What portion of the CRS name indicates this? Specifically, I'm wondering about a UTM system in Alberta, Canada. NAD83(CSRS)/Alberta 10-TM (Forest)
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1The key here is UTM, your angles and bearings won't be so great but distances should be fairly correct. Wiki has a fairly good article on map projections en.wikipedia.org/wiki/Map_projection that covers the basics.– Michael StimsonCommented May 16, 2016 at 23:47
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3Thanks! @MichaelMiles-Stimson I found this paper referenced in the article you suggested and thought it was worthwhile to post here. Dated perhaps, but quite helpful. pubs.usgs.gov/pp/1453/report.pdf– LisaCommented May 17, 2016 at 0:12
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2Raw list of readings here: github.com/mdsumner/reading-list/blob/master/projections.md - start at the top– mdsumnerCommented May 17, 2016 at 0:38
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1@MichaelMiles-Stimson : As a conformal projection, UTM preserves angles and bearings exactly.– Martin FCommented May 17, 2016 at 20:03
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1 Answer
From the links posted as comments I identified a couple of misconceptions I had about projections and gathered this quick summary.
It should be mentioned that many projections don’t truly preserve any attribute. Their intent is typically to minimize all types of distortion thereby not eliminating it in any specific property. Jack of all trades, master of none sort of idea. Also I want to mention most GIS environments group CRS by properties in one way or another. This can give a pretty good clue as to what you’re dealing with and what other systems it may be similar to. So it’s probably a good idea to start there.
Now on to answer the question, ‘Is there a place in the CRS name that indicates this?’ Yes, and no. Sometimes. If it is in the name it’s probably one (or more) of these cartographer words.
An Album of Map Projections, John P. Snyder & Phillip M. Voxland
If it’s not in the name, it’s probably just the guy’s name who came up with it. Projections like Robinson, or Eckert, or even Mercator come to mind. In these cases a quick internet search will likely get you what you need. And probably before too long you’ll be familiar with at least a few of them to have a general idea at first glance.
There’s also many other cartographer names for different things (like aspect), which give you other information about the projection but are not as explicit about distortion as the ones listed above.
As for the example of Alberta 10-TM (Forest). In this case distortion isn’t explicitly mentioned and this is where prior knowledge or the aforementioned internet search will come in handy. Like others pointed out, UTM projections are good at angles and are pretty useful when the area of interest has a primarily north-south extent – much like Alberta.