Real chalkboard made of5/26/2023 ![]() ![]() Using the chalky image as the picture fill for these polygons gives us a nice chalkboard-looking “basemap.” You can use whatever file you want, as long as it covers your whole view. I have a shapefile of continents, and a shapefile of oceans, which happen to combine to fill the screen. I’ve made a chalkboard texture image to fill my background shapes. Since I want the map to look as much like a chalkboard as possible, a simple black or slate colored background won’t cut it. Let’s style this sucker up! Did you know that you don’t have to use a solid color to fill polygons? You can use a hatched pattern (fun), a gradient (use judiciously), or a picture. Now we have some slightly weird, but more truthy, polygons. Running a “ dissolve by attribute” merges the geometry of same-named sites. The orange lines represent the within-site divisions that we’ll have to dissolve. Remember those pesky sites that had multiple places in their name (akron/canton, dallas/ftworth, etc.)? So far, we have a zone for each named place in a craigslist site. Don’t worry, Alaskans and Hawaiians, I’ve included you too, you just don’t play well for screen-captures. Using a “ clip” tool, we can chop off the parts of the polygons that don’t intersect land. Let’s pull in a shape of the US land and have a look. ![]() Speaking of natural barriers, the Thiessen polygons stretch out into the oceans. In real life, there are lots of practical conditions that would alter these, like natural barriers or road network conditions, etc. Thiessen (or “Voronoi” to non-map people) polygons divvy up areas that are considered the closest to a seed point, before getting closer to another seed point. Now for some whiz-bang polygon generation! I used the “ generate Thiessen polygons” tool. Fortunately for me, a cartographer, this means I marvel a lot. I marvel at the goodness of visualization every time a table is accribitzed into a map. While Craigslist shows their own point-map of sites, we need to be more specific, since we’re turning them into polygons. I went to Craigslist’s sites page, and copied all the sites for the United States, dropped them into an Excel table (splitting up all the multi-city sites) and geocoded them. Let’s take a crack at generating some new states, based on pragmatic economic zones. If you’ve ever read this book, or watched this show, you are keenly aware that the United States were carved out in a surprisingly arbitrary, and sometimes accidental, fashion. Ok, time to start dragging our fingernails down this map… How These States Got Their Shapes This will save you lots of time! Also included is the over-the-top-skeuomorphic image overlay with cute little pieces of chalk and dusty corners, etc. It’s not easy making a texture image that repeats without obvious edge patterns. This is the green chalkboard texture used for the background.
0 Comments
Leave a Reply. |