Our organisation have 6 Mobile Mapper 100 and 4 mobile mapper 120. Mobile Mapper 120 (around 4000$ with Glonass Option) And a Trimble Geo XT (around 8000$ glonass option) We use it to do forest inventory, the goal is to send people where we want them to go and not let them choose an area where there is less trees to count (because garmin or other old gps without glonass were not as precise and they had a distance flaws). 95% of the time, points are below a 3.5m distance of the intended target for all brand of gps after post-processing at the office (in the woods). Sometimes 5cm, sometimes 3.4m, it all depend of a variety of factors (weather, terrain, time of day, distance of the base for the post-processing correction, number of satellites, etc...) But the best of those kind of gps is thier accuracy in the field. You go right on the target. Best and bad of each GPS: Trimble geo XT = a tank, it's heavy and big but handled, it never miss to record data for post-processing. It's a little difficult to learn to use it but when you are use to it, you like it. Problem : Cost a lot, the internal software as a annual licence fee to upgrade it (around 600$-800$). Same for the post-processing software Trimble geo office (expensive annual licence fee). When you record, it record everything (bad or good signal) and you sort it with the post-processing software. it use waypoints thay you create with the post-processing software, that it's kind of pain in the ass to create. Why we have just one, because of the price.(and none of the companies that works with us bought it for the same reason) We can have 2 MM120 for the price of one XT. ------------------------------------------------------------------------------------------------------------------------------ MM100 (ashtech) and MM120 (spectra precision/trimble) are similar, the only difference is the présentation of the internal software. A littlle smaller very good GPS with SBAS/GLonass features. The good is you create your target (waypoints) in arc/gis and you put the shapefile in the GPS, for arg/gis user it's the best. Easy and user friendly. And the result is a shapefile/points with data for post-processing. You can choose your PDOP maximal and the GPS will not record the signal above it. For us, in the woods, we set up a pdop of 4 and 99% it works well. If we dont get a signal, we put it at 6 for getting a position (rare) The bad, is that sometimes (not often) it bugs for unknown reasons. you have to use it seriously, step by step like a robot. And sometimes the data for post-processing is missing...but never the shapefile/point before post-processing. The internal software is free of licence and free for upgrating as the software for post-processing. ----------------------------------------------------------------------------------------------------------------------------- I recommand all those GPS. Very accurate. We use them for a specific purpose but they can do lot more .
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