[aprssig] Tomtom's For APRS (Question)

[Bob Burns W9RXR]

At 01:48 AM 4/1/2012, Pat Cook wrote:

>How reliable are they?

They are probably as reliable as any other piece of mass-marketed 
consumer-grade electronic equipment.

Are they accurate? The "accuracy" of a GPS-based navigation unit 
depends on three factors: 1. the ability of the GPS receiver to 
acquire signals from enough GPS satellites to accurately determine 
the location of the GPS receiver, 2. the correctness and currency of 
the mapping data installed in the unit--an expensive nav unit that 
has two-year-old data may give you false information about the local 
road system, and 3. the ability of the navigation routing engine to 
determine the correct route from where you are to where you want to 
go. Of these three factors, only #1 matters for APRS.

Is a TomTom suitable for APRS? Only if it has a means for outputting 
NMEA 0183 data over an RS-232 serial connection at 4800 or 9600 baud. 
Virtually every APRS tracker/TNC on the market requires lat/lon data 
in the form of NMEA strings over a RS-232. Virtually every 
consumer-grade GPS-based automotive nav unit is _not_ suitable for 
APRS because they do not have this output. If the TomTom you are 
looking at does not have a serial port with NMEA output, then it is 
of little use for APRS.

The APRS Wiki has links to lists of GPS receivers that are suitable for APRS:

http://info.aprs.net/index.php?title=Hardware#APRS_Compatible_GPS_Units

These lists are by no means all inclusive, but it will give you some 
shopping ideas. The best bang for the buck, in my opinion, is a 
"puck-type" GPS receiver such as the Argent Data ADS-GM1 or Byonics GPS2.

Bob...