when using the trimble GPS you can also set one as base and leave it there to correct over the data you will recover with the other (active/ moving) Trimble GPS... but as you have heard... you need open areas to get this level of accuracy.
good luck! Bruno Ghersi Lima, Peru. 2012/10/28, Jay Guarneri <[email protected]>: > Tim: > > Differential GPS should get you that sort of accuracy in most situations > where you are not under dense canopy cover or in a canyon. You do NOT need > permission from the govermnent for that precision, as differential GPS is a > civilian workaround to get similar accuracy as the military-only GPS bands. > > At that level of accuracy, you would want a mapping grade GPS: standard > recreational grade GPS just won't cut it, and a survey grade GPS would be > overkill and way more expensive. I've only used Trimble GeoXH data > collectors, but I believe there are others on the market. They should come > with software that will allow you to set up data collection forms (data > dictionaries), plan for the best GPS measurement times, retrieve data from > the GPS, differentially correct it using the CORS (continuously operating > reference station) network, and export the data to a shapefile, table, > etc.. With good satellite geometry and no canopy or other obstructions, > you can get accuracies in the 10-20cm range without to much difficulty. > Recording more GPS readings per record (I usually use 30-60 for a point) > will improve your accuracy via averaging. Mapping grade GPS aren't cheap, > but I saw at least one used Trimble on Ebay. > > This tutorial should walk you through DGPS concepts: > http://www.trimble.com/gps_tutorial/dgps.aspx > > Let me know if you need any further clarification. > > Best, > > Jay > > > -- > Jay Guarneri > 403 S Main St Apt 1 > Monticello, AR 71655 > (631) 813-8218 > [email protected] >
