![]() ![]() If you don’t already have QGIS, download it now. We will be preparing the data using a popular open source GIS ( geographic information system) program called QGIS. For example, the administrative boundaries for the U.S can be downloaded from the Census Bureau. ![]() You can easily find Shapefiles for different administrative boundaries for free online. If you have your own location data in a spreadsheet you can follow this tutorial that explains how to convert a spreadsheet into a Shapefile. Despite its singular name, it is in fact a collection of files – with a minimum of four key files: (.shp. The data is in Shapefile format which is the de facto standard for sharing map data. The objective is to create a "heat map" that lets us see which counties have the highest number of colleges. The second dataset is US counties (polygon data).The first is US colleges (point data) which contains the locations of all US schools.To create our quantity map, we’re going to be using two datasets: Create an online quantity map of colleges per county Calculate the number of points in each county 3. In this tutorial, we’ll cover the following: 1. What we'll be creating today is an online Choropleth map, sometimes referred to as a Quantity map. In visual terms, the difference is quite clear: A heat map shows a change across a geographic landscape as a rasterized dataset–conforming to an arbitrary, but usually small, grid size. Renowned cartographer Gretchen Peterson, has a succinct definition:Ī choropleth map shows a change across a geographic landscape within enumeration units such as countries, states, or watersheds. Sometimes choropleth maps are referred to as "heat maps". Lucky for you, we've written a step-by-step tutorial to run you through the whole process of merging data from one shapefile into another, so that we have the required quantity data to create an online choropleth map. 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. ![]()
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