Choosing Contour Intervals for Dummies

Contour interval, shown on map legend

The staff here at the Antisocial Network long ago realized a simple truth: if you don't know anything about a topic, it's pretty likely that you not only don't know how to answer a question, you don't even understand what the person is asking. In case you haven't noticed, a lot of "answers" written by the contributors to the mother lode of misinformation, eHow.com, have precisely that problem – and today's DotD nominee is no different. Returning awardee Soren Bagley was obviously confused by the question "How to Calculate Contour Intervals,"¹ and his post (now at Sciencing.com) makes that pretty clear.

To be sure, this question is sort of ambiguous: if you know nothing about contour maps, you might think the question refers to determining the contour interval of a new map. In that case, the answer is, "Look at the legend, dummy!" People who've actually drawn contour maps might think it means "How do I choose a contour interval for my map?" which is a pretty good question. It's one that requires some knowledge of the range of contours, the size of the map, and the variability of local relief . In other words, it's like Justice Stewart and obscenity: you'll know it when you see it!

But that latter is too difficult for Bagley to cover in 300-500 words (not to mention that they don't study map design in English Lit), so he had to fall back on the stupidity defense, for which he was well-equipped. Yup, Soren says, "Contour lines are lines drawn on a map that indicate the elevation level of a geographical area. Contour intervals are the spaces between these contour lines..." ...both statements are utterly ridiculous: contour lines can represent any numerical quantity, not just elevation, and the contour interval is not the "[space] between... contour lines"! Once again, eHow's content editors prove worthless for correcting factual misstatements. More to the point, according to Soren,

"To prevent the map from becoming too cluttered, contour intervals are not always explicitly labeled with the interval that they represent."

Clearly, the boy does not realize that contours aren't always labeled with the value they represent. Ugh: this way lies madness...  We won't go into Bagley's long, drawn-out discussion of how to determine the contour interval by counting unlabeled lines between labeled lines, except to suggest that there has never in the history of contour maps (at least ones drawn by competent people) been a contour map with five unlabeled contours between labeled contours... What a yutz.
Around here, we think it's a good policy to never send a liberal arts major to do a STEM major's job, and Bagley has pretty much demonstrated why we have made that our mantra. Still, his only reward is another Dumbass of the Day award (number six for Soren).

¹ The original has been rewritten by the Leaf Group cleanup team, but it can still be accessed using the Wayback machine at archive.org. Its URL was   ehow.com/how_5344928_calculate-contour-intervals.html

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