Contours for the Dummy Topographic Map Reader

D and K are easy, Dave, but what's the elevation of A?

It's been a while since we harped on how cartographically illiterate the average person seems to be. Yeah, sure, we understand that a version of a Barbie doll once said, "Math class is hard!" but did any doll ever say, "Maps are hard"? What is it about maps that seems to turn off the brains of otherwise average freelancers? We assumed that a "former reconnaissance marine" would have a better than average understanding of "How to Determine Elevation from a Contour Map," but the David Chandler post at GoneOutdoors.com just plain disappointed us...

...Chandler's post disappointed us from his second sentence, in which David claimed that,

"A contour line connects points of similar elevation."

No, David, that's not correct: a contour line connects points of equal elevation. A contour line doesn't connect points with the values of 660, 658, and 663; it connects points with the values 660, 660, and 660! With that bit of stupidity completed, Chandler then explained the lines themselves:

"Index contour lines are labeled with their elevation value and are dark brown. Intermediate contour lines are lighter brown and are placed at equal elevation intervals between index contour lines. Supplementary contour lines appear at half the elevation interval of an intermediate contour line and are used in areas where there is gradual change in elevation."

A) intermediate contour lines are not "lighter brown," they are lighter weight. B) supplementary contour lines are dashed, if anyone cares (and Dave doesn't even mention hachured contours...) Once Chandler gets his glaring error and his lesser boo-boos out of the way, he gets down to business. It takes a total of 224 words, including some heavily gilded lilies, to get to his step 7:

"Add the product to the value of the nearest contour interval if your location is higher than the index contour line. Subtract if your location is lower than the nearest index contour line."

No duh... except for one small problem: his instructions, wordy as they are, only tell someone how to determine the elevation of an unlabeled contour line. Chandler says jack about finding the elevation of a point that is between contour lines! Idiot!

The word David wanted was "interpolate," but he never used it. To estimate the elevation of a random point on a topographic map, you must interpolate an intermediate elevation value based on the distance between the two closest contour lines and the direction of the slope. Chandler wrote all that rubbish and never got to the point – typical Dumbass of the Day work.

copyright © 2018-2022 scmrak

DD - MAPS