In a spreadsheet, this would be simple enough - just copy the entire count column from the college spreadsheet, and paste in the County spreadsheet.īut when dealing with spatial files, it's not quite that simple. To create a quantity web map, we need a numerical column in the County data that lists the schools per county. The points aren't in the county layer, so there's no way to create a choropleth map showing the quantity of schools per County. We’ll just go to the layer style settings for the counties and select the points and… wait. Now, say we want to shade each county by the number of colleges. From the point markers we can see that some counties have lots of colleges, some have fewer. Let's say points are all the colleges and universities across the US, the the polygons are all the counties in the US.Īdding them both to a web map will give us two layers. Sometimes it just all comes together and we’ve got everything we need to make a great map: we’ve got a spatial file with our points, and we’ve got a spatial file with our regions. This tutorial will show you some GIS magic to get a count of markers in a county and create a stunning quantity map for your online GIS.

Depending on what we're trying to visualize, we might find that we're missing a key attribute, or that the data we need is in a different dataset.

Magic maps tutorial