Data Hacking

162 Part II — Software Hacks
You may also find a positional error. Positional errors are likely caused by GPS errors or communication
errors. Try these steps to resolve the problem:
1. Ensure that the cable is properly connected at both ends. Problems here can cause data
corruption and a degradation of signal quality.
2. Verify that the GPS has a clear view of the sky and is receiving a good signal.
USB-to-Serial Converters
If you are using a USB-to-serial converter, you might encounter a few problems specific to your
setup.
For example, you might find that the number assigned to the port creates changes occasionally,
and you might have to reconfigure any software you are using if this has happens.
Another problem is that a USB-to-serial converter can assign ports from COM 1 to COM
255. However, some software packages can only use ports 1 to 4. Most modern applications
allow you to choose any active port for GPS communication, but if you use an older software
package you might be limited to ports 1, 2, 3, or 4.
Only versions 4.0 and later of the Garmin MapSource mapping program will interface with a
GPS through a USB-to-serial connector. Any previous versions will fail to work.
USB-to-serial converters are not supported in Windows 95, even the OSR 2.1 version that
included USB support. You will need a minimum of Windows 98.
Summary
This chapter looked at problems you might encounter when transferring data between the GPS
and a PC or handheld device. As I’ve said a few times, you don’t have to have a connection in
place, but it makes life a lot easier and enables you to process and display data in a much more
versatile and customizable way than is possible with most GPS units.
If you are unfortunate enough to have problems with your connection, following either the
generic or specific instructions in this chapter should help you fix the problem and get your
system working again.