Mapping Hacks

Connect to Your GPS from Multiple Applications #57

Chapter 5, Mapping with Gadgets

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HACK

If this happens, it’s because gpsd was written against gcc headers that your

particular system no longer supports. Fortunately, this is easy to fix. Run the

following bit of perl, and then run make again. Everything should build just

fine:

$ perl -pi -e 's/varargs.h/stdarg.h/g' *.c

$ make

Running gpsd

First, you’ll need to make sure your GPS receiver is on and properly con-

nected to your computer (see “The Serial Port to USB Conundrum”

[Hack #50]

if your computer doesn’t have a serial port). Next, you’ll want to be sure

your GPS receiver is configured to output NMEA-0183. Chances are good

that the GPS receiver has an option for this in a setup menu, but check your

owner’s manual to be sure. Several new models of Garmin GPS units no

longer speak NMEA. There is discussion of extending gpsd to support the

proprietary Garmin protocol, but if you are in the market for a new GPS,

you may want to add standards compliance to your list of purchase require-

ments!

NMEA-0183 is an industry-standard protocol, published by

the National Marine Electronics Association, for transmit-

ting position data over a serial line. The protocol consists of

a continuous stream of ASCII text “sentences,” sent at 4800

baud, that convey not just position information but poten-

tially also accuracy, speed, bearing, time, satellite visibility, ...