Coordinate Conversions for Dummy Cartographers

topographic map

One of the staffers is a map collector. Whether it's AAA state maps, USGS topo maps, gas station city maps, or whole-state gazetteers; she's a fan. As a result, she knows quite a bit more about maps than the average bear; so when she runs across utter bullshit about maps she's in a hurry to point it out. The other day, our map fan turned up a Leaf Group rewrite special that, to be charitable, was moronic. Meet Lisa Maloney and her ill-considered attempt to rewrite the Sciencing.com post, "How to Convert Eastings and Northings."

Maloney's task was to rewrite an original by Kelvin O'Donahue that, according to the map lady, was well-nigh flawless. O'Donahue pointed out that, in the world of maps, easting and northing are the X- and Y-coordinates of a map projection such as Universal Transverse Mercator (UTM). According to Maloney, however,

"Eastings and northings are simply x and y coordinates, just as you'd use on a graph – but they can be overlaid on different coordinate systems as a way of designating specific places on the Earth's surface."

"Well that's stupid," our map fan snorted. "Eastings and northings aren't 'overlaid on different coordinate systems,' they're measurements within the coordinate system. Sheesh!" More derision ensued when the young woman noted that Lisa referred to something she called the "State Place Coordinate System (SPCS)" not once, not twice, but three times; mangling the name of a state plane system every time. What's most amusing is that Maloney actually got "plane" right... once.
Maloney was sort of on track when she said that,

"The SPCS system is literally a Cartesian graph or grid system – but its origin is located in such a way that the primary area being measured is always located in quadrant I of the graph, or the area where both x and y values are positive."

The "quadrant I" information is accurate, but that business about a "Cartesian graph" system? Definitely an undersell. She also goes on at length about how the origins of different state plane systems are at different locations, which – gasp! – is also accurate. Where Lisa fails in her description of SPCS is the lack of information about map projections. Maloney says not one word about why different states have different state plane coordinate systems, doesn't mention that some states have several state plane systems, and never says that not all of them use the same map projection.

In fact, the only map projection Maloney mentions in her post is UTM, and – again – she neglects to mention that the projection is an attempt to display arts of a sphere on a flat piece of paper; something she should have picked up from O'Donahue's version. She also misinform her readers by claiming that, "In order to use northings and eastings with UTM coordinates, you need to know two things: First, which of those 60 zones you're in; and second, where you are in relation to the central meridian of the zone and where you are in relation to the equator."

Yes, knowing which zone you're in and whether you're in the northern or southern hemisphere is critical to a UTM projection, but "where you are in relation to the central meridian"? Someone should tell our Dumbass of the Day that the northing and easting values are what tells you that!

copyright © 2019-2022 scmrak

SI - MAPS