Mapping Hacks

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Chapter 5, Mapping with Gadgets

#62 Build a Car Computer

HACK

This code requires a Python module called pySerial. This module is avail-

able at http://pyserial.sourceforge.net/.

Displaying GPS Data in a GUI Application

Text-based mapping software is not very exciting. A more useful approach is

to render map data onto a 2-D window. In the following example, we will

see how to build a cross-platform Python application that uses the Tkinter

GUI library to display GPS data, with the ability to zoom and pan.

Figure 5-42 shows this application displaying a captured GPS session along

with Wi-Fi locations located using NetStumbler (a free wireless-network

sniffer for Windows). You can also use this program to display waypoints

captured on a hike, general points of interest, geocaches, and so on.

It is easy to be intimidated by mapping software, but it is really quite simple

after you master coordinate conversions. There are two coordinate planes

involved in our application: the latitude/longitude plane and the x/y pixel

plane on our GUI drawing surface. Real-world coordinates are bounded by

(–90,–180) and (90,180), whereas GUI surfaces are bounded by (0,0) and

Figure 5-42. Our sample application displaying a GPS log and Wi-Fi hotspots in the area

Build a Car Computer #62

Chapter 5, Mapping with Gadgets ...