Monday, November 7, 2016

Crime Analysis with Google Earth

I originally wrote this post for a software company’s blog in 2014. This company was bought out and recently their blog and website have been removed from the web permanently. I am reposting it here for posterity. 

I am very fortunate to work for an agency that can provide a lot of very nice tools with which to do my job. We have a full blown enterprise Geographic Information System or GIS along with quite a number of features and enhancements for it.

What's funny is that while I have and use this very powerful GIS, I often find that most of the mapping tasks I need to perform don't require that kind of sophistication. Firing up the GIS application just to locate a street is kind of like swatting flies with a shotgun. The tool I turn to most often for simple mapping tasks is Google Earth.

There are a lot of advantages to using Google Earth for many tasks. Here's a few:

Cost: The basic version of Google Earth is free. Not only the application itself but the data it uses, streets, satellite imagery, etc. If you've ever purchased GIS data you know that it is not cheap. The same goes for GIS applications, extensions, etc.

Ubiquity: Since Google Earth is free and it's offered on a number of computer platforms, it's very easy to share data with another user. You can create a map and save it as a .KML file and then you can email the file to them. No worries about file format, data compatibility, projection, etc.

Ease of Use: Unlike a GIS application with a steep learning curve, a Google Earth user can map meaningful data very easily. Google Earth is often used in grade schools and secondary schools to help kids learn geography. If a school kid can learn it, we should be able to figure it out.

So what kind of maps can we create with Google Earth?

The most basic map is just one that shows geographic features such as streets, lakes, etc. Maybe you just need a simple map of a neighborhood showing the streets in it.

You can also create a point map. Maybe you have a series of armed robberies that you want to look at to see their geographic relationship. You can use the "Add Placemark" command to place  marker at a location, give it a location and an icon. Do this for all the robberies and you have your map. The downside is that the free Google Earth does not come with the ability to batch geocode. If you have hundreds of points to plot you'll have to turn to an outside tool or upgrade to Google Earth Pro.

You can create boundary maps by drawing polygons on the map with the appropriately named "Add Polygon" tool. This works great for drawing beat boundaries, enforcement zones, etc. You can label these polygons and set the colors and symbology to create your maps.

It's also possible to draw maps with routes using the "Add Path" tool. This works well for creating maps of parade routes, maps showing the route a criminal took between crimes, etc.

Another feature I use quite often is the "Show Ruler" tool. This tool allows you to measure distances on your maps. There are a number of criminal law penalty enhancements in Texas that increase penalties for offenses if they occur within a specified distance of a school. This tool allows you to easily determine just how close the offender was to that certain geographic feature.

Google Earth also makes it very easy to export your map as an image file that you can then drop into a report or presentation. I use this feature quite often when I create briefings on crime series or other types of bulletins. The old adage about a picture being worth a thousand words is true. By including maps in your presentations or briefings you can easily communicate geographic relationships. They also make your reports visually appealing.

Since I have access to GIS, I also use it to help create content layers for use in Google Earth. I use ESRI's ArcGIS which comes with tools that will convert GIS layers to Google Earth compatible formats. For instance, I'll export our city limit boundary file from GIS to Google Earth so I can easily add it to Google Earth maps. I have also done this with our Beat Boundaries, Policing Districts, etc. These two tools work very well together.

Do you use Google Earth as part of your crime analysis toolbox?

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