Geolocation in iOS

Chapter 6. Drawing Heat Maps

One of the more obvious missing features of the Map Kit framework is the ability to render heat maps on top of map views. However, while you’ve only met polygon overlays so far (see Chapter 3), it is also possible to use the overlay images on top of maps. You can use that to draw heat maps on top of your maps that will be fixed in the map view and move around as the user scrolls the map back and forth.

Note

The demonstration application we’re going to build in this chapter makes heavy use of heat map code written by George Polak at Skyhook Wireless. Thanks to him and the all the team at Skyhook Wireless, both for the code and assistance. The SHGeoUtils class is copyright Skyhook Wireless and used with permission; it is distributed under an MIT license.

Building an Earthquake Map

You’re going to build a demonstration application with a heat map from data representing the Richter scale magnitude of a recent earthquake in New England.

Open Xcode and choose Create a new Xcode project in the startup window. Choose the Single View Application template from the iOS section of the New Project popup window. When prompted, name your new project HeatMap. In the Company Identifier box, enter the root part of your Bundle Identifier (see the iOS Provisioning Portal) used in your Provisioning Profile; for me, this is uk.co.babilim. You should leave the Class Prefix box blank. Ensure that the Device Family is set to iPhone, the checkbox for ARC is ticked, and the boxes for ...