Making maps from Tompkins County GIS data

I did not, thankfully, have to create the map on the ward page manually. Tompkins County Geographic Information Services provides publicly accessible data you can load into Google Maps to provide views tailored to your needs.

What were our needs? The city website provides a serviceable ward map, but as a PDF it’s not interactive and provides limited granularity (i.e., you can’t zoom into streets and properties). It also doesn’t clearly mark the city’s wards, and I wanted something that made that more explicit. Our ward map takes advantage of Google Map’s flexibility and familiarity to (hopefully) provide an easy-to-read and easy-to-use visualization of the city’s election districts.

You can do something similar with the other data that the Tompkins County GIS page provides. Here I’ll walk you through how to take shapefile data from public sources and import it into Google Maps to display it.

Getting the Data

You of course start with the information you’re trying to map. For this example, I went to the GIS Data page and clicked on Tompkins County GIS Datasets at CUGIR to get to the Cornell University Geospatial Information Repository. That particular link takes you to popular datasets, including what I’m interested in: Election Districts, Tompkins County, 2013. Whatever you happen to be interested in, download the associated zip file.

Converting the Data

The shapefile format is used by GIS software that most of us don’t have access to, the skills to use, or a reason to care about. All I really know is that Google Earth and Google Maps take KML files and that I need a way to turn those shapefiles into KML.

There are various standalone programs and plugins to professional software that do this, but the easiest way I found was to use this online converter by Mapsdata.

converter screenshot
From the converter at mapsdata.co.uk

Drag the zip file you just downloaded into the box on the website or click the button to bring up a file browser to find the zip file. Either way, you’re given a KML file to download.

Importing into Google Maps

Go to Google My Maps to create a new custom map.

Google My Maps screenshot
My Maps splash screen

Click Import to upload the KML file you just downloaded.

Click Import to upload your KML file
The Import link will bring up a dialog to upload your KML file

Wait a little while and see your map appear!

Import complete: basic outlines displayed
Import complete: basic outlines displayed

By default Google Maps just outlines the geometric boundaries of whatever regions are contained in the data. But also in that KML file is metadata associated with each region. In this case, information about each election district. You can use that metadata to color the map in a more useful way.

Click on the paint roller or the “Individual styles” text next to it. In the pop-up menu that appears, click on the box below “Group places by” to display visualization options. Here I want to group by ward.

Options under "Group places by"
Options under “Group places by”

When you’ve chosen a field to group by, Google Maps will assign a color to each. You can easily change these to meet your needs.

Much easier to look at
Much easier to look at

Pretty easy, right? There are other options for coloring the map and displaying labels. Play with it until you’re satisfied with the way your map looks. Then hit that Share button to embed your map in a website or distribute a link.

I hope this helps! Together we can better visualize the available city and county data to keep residents informed.