The GeoXT is the most accurate and precise GPS on the market. As you = are probably aware, when you record a data point using a GPS unit you = can have varying degrees of accuracy and precision. Most of the = over-the-counter GPS are fairly simple to use, but also give fairly = unreliable data. They average all of the datapoints together. In order = to have a true 95% precision you must record about 150 data points when = you log your location, for a 99% precision you must use 180 data points. = You cannot do this with Garman or Magellan. This data distribution = then allows you to manually correct your data and even remove = influential outliers for good reasons. Most Garmins and Magellans = automatically remove the outliers and do averaging so you have no idea = what the real data looked like. It gets even worse if you are dealing = with a 3D environment such as in the mountains. In other words, if need = to get back within 3 ft of your location, you better use a Tremble = Geoexplorer XT or comparable GPS. If you only need a rough idea of = where you are, any will do. But a garmin can get you anywhere from 3ft = away (on a perfect day with no canopy) to a football field away. You = should talk to a rep about the differences and they should be able to = explain it to you. Or talk to a GIS guru. When I was working on NPS = work, they required Tremble. =20 =20 Malcolm L. McCallum Assistant Professor Department of Biological Sciences Texas A&M University Texarkana 2600 Robison Rd. Texarkana, TX 75501 O: 1-903-233-3134 H: 1-903-791-3843 Homepage: https://www.eagle.tamut.edu/faculty/mmccallum/index.html =20
________________________________ From: Ecological Society of America: grants, jobs, news on behalf of = Arvind Bhuta Sent: Mon 3/27/2006 2:41 PM To: [email protected] Subject: GPS units and accuracy data 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?=20 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.=20 Also, what is the spatial accuracy compared to sub-meter GPS units. I = would assume that it couldn't 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
