Cross-Sections for Dummies

cross sections have internal detail

Once our staffers have tagged potential DotD nominees for the next nomination round table, they go straight back to work looking for yet more laughable efforts by freelancers. Often, the piece they just finished reading will prompt another search term; which is exactly what happened with today's nominee. Research staffer "R" had just read some WiseGEEK dreck about section lines, which prompted him to see what kind of damage eHow.com's contributors had done to the concept of cross sections. Sure enough, first-timer Ana Sol was there to help with "How to Draw a Cross Section."¹

Just why a fashion blogger decided she knew anything about drafting and maps is a mystery to us, but her introduction is pretty much a dead giveaway that Sol was well out of her comfort zone. After all, only someone entirely unfamiliar with cross sections (or perhaps it's just geometry) would explain that,

"Cross sections, or schematics, are two-dimensional drawings that show a side view of an object sliced at a specific point."

Some corrections for Ana: A) a cross section is definitely not the same thing as a schematic, and B), a cross section does not show a side "at a specific point," it shows a side view along some arbitrary plane.  Sol continued her intro by, for some unknown reason, babbling about drawing a cross-section of a set design for the theater – a strange choice of examples, given that none of her references says anything about a set!

Some of Ana's more bizarre claims follow:

• "[T]he cross-section line... needs to be a straight line that can be viewed straight-on despite changes in shape of the surface." – First, cross sections are not always straight lines; second WTF is the crap about "changes in shape of the surface"? Isn't that the point of a cross-section?
• "Draw a frame for the cross-section. The frame should have three sides: left, right, and bottom. The bottom line represents the same line from Step 1 as overall width. The lines on the sides are there to help you with height. Your frame needs to be in the same scale as the drawing you are working from." – Clearly, Ana has never heard the term "vertical exaggeration."

"Use the frame like a graph to draw points along the cross-section line. You may want to start by drawing equidistant points on your line from Step 1. At each point, determine the height of that point and plot it in on your cross-section frame by measuring the distance of the line on the cross-section line so that it's the same as on the base line, and then measure vertically on the frame to the correct height. If there is a significant increase in height, or change in contour, draw in more points along this part so that you end up with the most accurate schematic view possible." – This one, Sol harvested from an article on drawing a topographic profile. Ana's problem is that all this would do is draw a profile of her object, not a cross section. Sol's curious desire to blather about drawing a cross section of a vase (ummm, no...) and her equally curious focus on theater set design are overshadowed, however, by the fact that she doesn't actually explain how to draw a cross-section. Why do we say that? because her drawing, such as it is, lacks any internal detail. The whole point of a cross section, is that such drawings, to use Ana's own words, "show a side view of an object." We would like to think that Ana knows that even the most prosaic object – say, a vase – has some measure of internal detail. On second thought, perhaps even an M.A. in "educational theater" is insufficient to teach as Dumbass of the Day about such realities...

¹ The original has been deleted by Leaf Group, but can still be accessed using the Wayback machine at archive.org. Its URL was   ehow.com/how_8549255_draw-cross-section.html

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