As a spatial professional, projections and geodesy have become second nature to me – often to a point that I take them for granted.  In many cases, the projection becomes like a font in a presentation – if you used Helvetica on page one, you had better use it on page two.  Generally, the consistency is more important than the overall effect.  When it comes to fonts, there’s only a handful of professional looking typefaces to choose from, and one is little different from another.  Projections can sometimes feel this way, especially if you spend most of your time looking at similar projections, such as adjacent state plane systems.

Occasionally, though, you get a chance to see just how much difference a projection can make.  Over the weekend, I downloaded a grid of bathymetry and hypsometry of Michigan’s Great Lakes from NOAA’s NGDC Grid Translator.  The grid was in geographic form, but had neither projection nor datum applied to it – just raw latitude and longitude.  The raster I created from it looked somehow flattened and lazy:

This is a reasonably accurate view of the area, but it’s not the view we’re accustomed to seeing.  Although a worldwide coordinate system might make sense when viewing a whole hemisphere, a localized projection that minimizes certain kinds of distortions is more suited to a smaller area.  As it happens, most of Michigan’s Great Lakes happen to fall within Universal Transverse Mercator (UTM) Zone 16.  Which gives a much nicer looking image:

This is more like the Great Lakes most of us recognize.  The UTM projection preserves the shapes and angles our eyes have grown accustomed to, at the expense of distance and area.  Notice, of course, how this image looks more like a slice from the outside of a sphere, unlike a typical rectangular map.  Although I wouldn’t normally use this kind of shape for a presentation map, I think it illustrates nicely just how the UTM projection modifies the mathematics of the raster to create the correct image.

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