Using the Pro XRS System for Locating Points, Lines, or Areas in 3-Space

The Pathfinder PRO XRS is one of Trimble’s mapping grade GPS systems. We have two of them, Avocet and Bobolink, and they can be configured a number of different ways to acquire GPS data at different levels of uncertainty. The complete setup consists of an antenna connected to the receiver which resides in a backpack, a handheld data collector, and batteries (which regularly need recharging). Most of your interaction will be with the data collector and the affiliated software package, Pathfinder Office.

In the Lab

• Planning a survey with Quickplan software
• Remove the batteries and put them back in the charger when you return from the field. Do not leave the batteries connected to the instrument - they will be discharged.

Options in the Data Collector's Main Menu (Lab or Field):

• Configuring the Pro XRS’ Data Collector for Real-Time Data Collection at Survey Points
• Checking Satellite Information - shows where visible satellites are in the sky.
• Checking Receiver Status - gives fairly self-explanatory statistics.
• Using the File Manager - rename files, delete files, transfer data, or select data dictionary (see manual).
• Collecting Data - Trimble thinks of points, lines and areas as being "features" (e.g. "Point Feature" means point):
  • Points - this is the normal mode for gravity stations, etc.
  • Lines - for mapping a path, ridgeline, etc. This is not much different than collecting Points other than you select Line Generic rather than Point Generic in the Start Feature menu discussed under Points. In Configuring you will need to select the sampling rate that is correct for your experiment. Then walk out your line while the recorder collects points.
  • Areas - for measuring areas, outcrops, etc. This is not much different than collecting Points other than you select Area Generic rather than Point Generic in the Start Feature menu discussed under Points.

Downloading Data From the Data Collector to the Lab PC with Pathfinder Office

• Start Pathfinder Office - it is installed on Veruna.
• When Pathfinder Office asks you for a project name, hit the New Button and make a project with your name or go to one you already have named. Keep the directory structure clean and orderly.
• Plug the data transfer cable into the Data Recorder
• Turn on the Data Recorder. It will try to connect to the GPS unit - Hit ESC to stop it from trying to connect to the GPS system (or wait it out).
• Go to the Data Recorder's File Manager/Data Transfer menu
• In Pathfinder Office go to Utilities/Data Transfer. It should tell you it is connecting to the data recorder. When connected, your rover files should show up in the Available Files box. If it isn't working make sure DEVICE = GIS LOGGER in the Pathfinder Office Export window.
• Select and Add the files you want to transfer
• Set the Destination directory - it should do so on its own.
• Hit the Transfer Button and Pathfinder Office does the rest while you watch the progress bar. Your data are now in your subdirectory (project folder) on Veruna.
• When Pathfinder is done, hit disconnect and close the window.
• If you will be differentially correcting those data you will need to get the appropriate base station data from the USFS. Otherwise, you are ready to proceed to Exporting Data from Pathfinder Office.

Acquiring Base Station Data from the County for Differential Corrections (the old USFS station is defunct)

• You have to wait an hour or two in order for the appropriate base station files to get uploaded to the county site. The rover files are stamped (named) with local time to help you remember where you were. The USFS base station files are in Greenwich Mean Time (GMT) which is 7 hours ahead of Mountain Standard Time (MST) and six hours ahead of MDT.
• Once the files are uploaded to the county server they will appear there with names that encode the day, time and date. Select those that overlap your data. If you miss this on the first try, Pathfinder Office will tell you that you do not have complete coverage for the differential corrections.
• To download a base station file, just right click on it, select "Save Target as" and specify the Base Station subdirectory under your project folder; double clicking works too. These are .EXE, self-expanding compressed files.
• To expand the base station file once it is in your subdirectory, open windows explorer, drill down to your subdirectory, and double click on the basestation.EXE file and it will self-expand. You will then have two base files with the same name but one will be .SSF and the other .EXE. You can delete the .EXE's once they are expanded as Pathfinder Office works on the .SSF files.
• Additional base station data are available from Lewiston and Helena

Differentially Correcting Carrier-Phase Data to get Sub-meter GPS locations

• In Pathfinder Office's menu bar click Utilities/Differential Correction and you get the Differential Correction window.
  • Select the Rover files you downloaded that you wish to differentially correct. If you do more than one at a time Pathfinder will run all the results together into one file. So if you want to keep things separate, differentially correct your files one at a time. This can be annoying because of Pathfinder's desire to name all exported files the same thing (posnpt.dat) - so rename them in Windows Explorer, with rational names as you go. Basically just keep track of everything as you will have a bunch of files.
  • Select the Base Files from the Base subdirectory. Pathfinder will popup a window that tells you if you have 100% coverage or not. If you do not have 100% coverage, you need to download another base file from the USFS or county. Click OK.
  • Pathfinder then pops up the reference position window which gives the base station's position. Whether you are using the USFS files or Missoula County files, leave this as it is. If you happen to be working with our older files using USFS base station information, you have to correct its mislocation later as the USFS antennae was mislocated about 1.16 meters too low. If you are using the USFS files, just add 1.16 meters in one column in a spreadsheet rather than sometimes doing it here and other times forgetting to do so - make it an obvious column in your spreadsheet and mention it in your report. Click OK.
  • Let Pathfinder put the corrected files in the Output folder in your project.
  • For Processing, pick Smart Code and Carrier Phase Processing.
  • Click OK and Pathfinder starts processing.
• When Pathfinder finishes you have a new, differentially corrected file with a .COR file extension; that's the one you want to export.

Exporting Data from Pathfinder Office for Spreadsheet Manipulation

• Start Pathfinder Office and, when the initial screen appears, open your project folder.
• Go to Utilities/Export on the menu bar
• In the Export Popup Window:
  • Browse the folder under Input Files and select the file (file_id.COR) you wish to export data from (it is probably the default).
  • Set the output folder. Just use the default which is a subdirectoy under your project, called export
  • Hit the Change Setup Options command button to make sure those parameters are set correctly.
  • Hit OK to create the export file. Watch the progress bar.
• When your file gets "exported" to the "export" subdirectory under your project name, the file ends up being named "POSNPT.DAT" for some peculiar reason that Trimble likes...
• You now have differentially corrected, carrier-phase data. Import the file POSNPT.DAT into Excel to average results, calculate standard deviations, etc. If everything was done correctly then the exported file should be in these coordinates: