blunoz

I own a Garmin GPSMAP 60CSx. Overall, I am very pleased with it. In my opinion, the SiRF III chip does NOT get you more accurate fixes. What it DOES enable you to do is get a fix under a tree canopy or amongst tall buildings were my previous GPSr would not have gotten any fix at all. So in this sense, SOME fix is better than NO fix. In the woods in the winter before the trees turned green though, I actually found my fixes were LESS accurate. The problem is that the SiRF III chip is so sensitive, it picks up multi-path arrival. In other words, it picks up the very weak signals from the satellites bouncing off the trees (or buildings), which introduces a time delay error in the signal and degrades the position accuracy. Like I said before, this is a GOOD thing under a tree canopy or amongst tall buildings because SOME fix is better than NO fix. However, I have found in situations where I have a clear view of the sky and can readily receive the strong direct-path signals from the satellites, if there are a lot of trees or obstacles around, the GPSr also receives the multi-path bounces. The result is if I stand in one place, my plotted position will wander around the map a little bit. It would be nice if in the next upgrade Garmin does if they would make it so you could adjust the threshold sensitivity of the receiver so that if you HAVE good strong direct-path signals, then you could tell it to ignore the weaker multi-path bounces. If you go to the NoVAGO (Northern Virginia Geocaching Organization) yahoo group, message 343 gave a link that compared the performance of the Magellan to the Garmin, and it showed graphs of the Garmin's position wandering around like that. You'll also see the follow-on rebuttals to that posting talking about how the data could be misrepresented. Kevin / Blunoz

Unfortunately, it's not a cheap or readily accessible solution, but if you know anyone who has ESRI's ArcGIS software, it can do all the things you are talking about. It's a very powerful Geographic Information System software package that we use at my work. Of note - I just finished taking an online class in ArcGIS where they provided us a copy of the ArcGIS software and a "student" license to use it for the 3 month duration of the class. It was a really good class. A lot of major universities like Penn State are offering graduate certificates in GIS now. Anyway, like I said, I know it's not cheap, but if you know anyone in your local county planning office, you might ask if you could sit and use their computer for a half hour or so. (It was actually a friend of mine who works in a county planning office that introduced me to GIS). Kevin/Blunoz