There is really no comparison between a Trimble GeoXT and one of the less expensive Garmin or Magellan units. At best, with WAAS enabled, you can obtain 2-3 m accuracy horizontally (and around 4-m or so vertically) with a Garmin or Magellan. Post-corrected data using a GeoXT can be sub-meter, and using a GeoXH can be on the order of 30-cm. There are several factors that drive the differences in accuracy of these units. First, there is NO way to post correct data collected from a Garmin or Magellan unit. You are stuck with the data that you have collected. Second, although your Garmin might tell you that there are 8 satellites in the sky, it likely isn't using all of them to calculate your position. The accuracy obtained from post-corrected data using a Trimble unit will be a function of number of points collected, distance to the nearest bay station, and the number and position of satellites in the sky during your data collection. Now, all of that said, you also need to think about the resolution of the GIS data that you are using for your analysis versus the GPS data that you are collecting, and the question that you plan to address. If you are using 30-m or 10-m DOQQ data, for instance, 30-cm GPS data might be overkill, or sub-meter might be overkill if you are tracking the movements of large ungulates (or something), in which case 1-m, or even 2-3-m might be good enough.
Mike Quoting Arvind Bhuta <[EMAIL PROTECTED]>: > Forumites > > I wanted to find out more about GPS units, a topic many people have asked > about on this listserv in the past. What I am trying to figure out is the > accuracy between an item like the Trimble Geo-Explorer XT compared to > something more economically available like a Garmin 12 or Magellan product? > Are people happy using simple GPS units like the Garmin 12 to collect data > especially if you want to conduct geospatial analyses and if so how do you > deal with spatial accuracy and post processing data if it can be done. > Also, what is the spatial accuracy compared to sub-meter GPS units. I would > assume that it couldnt but it might also be difficult to do. I know the > Trimble GPS unit and Pathfinder Office makes this easier and you have better > accuracy and precision, you even get a root mean square error with you data > so that could be discussed. I appreciate any input and help from any one and > look forward to hear what has to be said. You can reply to me and then I > can summarize what was said to the listserv if need be. > > Thanks, > > Arvind > > > Master's Student > Department of Geography > Virginia Tech > http://www.geography.vt.edu/people/Grad%20Students/bhuta.htm >
