map trouble

I read a blog post a couple weeks back (sorry, I can't remember where) about trying to make sense of conflicting data on a topographic or geologic map. It’s true that sometimes you find yourself floundering of a thicket of aerial photographs, geologic maps, and your own (or someone else’s) mapping notes.

In the modern era, it seems like this problem shouldn’t come up. We can pull up aerial photos from google earth and other sources, and we have GIS to pull all the different layers together, right?

Well, that’s the way things should go. But sometimes you inherit a project that has conflicting spatial data. It all looks good when you look at the figures, but when your surveyor goes out and adds some new locations or you read their own survey reports, you find that your site appears to have a major fault running through it. It’s worse if everything looks subtly distorted when you import it, because then it’s nigh-impossible to figure out what’s causing the error. In worst-case scenarios, the only solution is to go out and re-survey every blessed thing, but that’s not feasible for some large-scale projects.