Sunday, December 18, 2022

Local Paper Maps: Finding Them

This post is part of a series on creating and using local printed maps. Start here.

As I mentioned in my opening post on this topic, finding local US maps is relatively straightforward. Head over to the USGS and download a freely available 7.5 minute quadrangle for your area of interest. In practice, there are some steps you can take to vastly streamline this process.

First off, you should watch this USGS tutorial: Lesson 4a – Using The National Map Download Application. When I initially saw 'download application' I imagined some crufty Windows program I would have to download to access maps. But that's totally wrong; the 'download application' is merely a straightforward webapp.

One point of confusion is that the USGS has a number of websites that offer map downloading capability. There's this slick site let's you explore both modern and historic maps. You can fiddle with the opacity of the maps to visualize different eras in one view.

And then there's the National Map Viewer, which allows you to visualize different layers of map data, as well as measure distances, elevations and overlay data sets on a map.

However, if you're interested in downloading maps, you really want to make your way to this relatively basic looking downloader site. This site has two useful tricks up its sleeve to help us in the local maps department.

First, you can opt to show just 7.5 minute topo maps, the type we're after. Next, you can opt to show just recent versions, which cuts down on having to wade through multiple years of these maps. In this screenshot I'm asking for the USGS to tell me which up to date topo maps define the area that is the DC Beltway.

The other notable feature of this site is that once you see a list of maps, you'll see both download links and the ability to add the items to a cart. If you're downloading a single map, by all means click the download link. But in my case, I've got 20 different maps to download. Rather than add them one-by-one to the cart, I can click the relativey subtle 'txt' link provided:

Doing so will download a text file where each line contains a URL to a single map. It's then trivial to use a tool like wget to download these files in bulk. Note: the downloaded text file has DOS style end of lines, so the first order of business to use this file on Linux was to strip these.

$ dos2unix data.txt
dos2unix: converting file data.txt to Unix format...
$ cat data.txt
$ for u in $(cat data.txt) ; do wget $u; done

I've now got my maps. Next up: preparing them for printing.

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