Basic Setup of the Trimble Pro XR GPS - Startup
III. Startup
Once all connections are made, take the ProXR out into a relatively open space to see if it is working properly.
A. Turn the unit on
1. Put on the backpack so that the antenna is properly positioned above your head.
2. Press the green button on the datalogger as shown below. Two introductory screens will appear before the main menu pops into view.
Above: The green start button. Below: The first of two opening screens. Allow both of the startup screens to load and pass, and the main menu will then pop up.
Below: The main menu. The message "Connecting to GPS" will appear as the receiver collects GPS data.
B. Understanding the Main Menu Status Line
After the receiver has collected sufficient GPS data, the status line in the bottom area of the Main Menu will display information on the status of GPS.
1. Battery Charge (Far Left)
Displays the relative charge of the batteries. If the battery is running low, you may simply switch the battery connections in the backpack to 2 other batteries. You need not worry about the GPS shutting off as you switch backpack batteries, as there is a smaller battery in the datalogger that will run the GPS while you change your connections.
2. Beacon Signal (Second from Left)
This icon appears when the receiver is obtaining the differential corrections from a radio beacon. This is necessary to acquire the most precise data possible. If the icon does not appear, it could be due to
a. no radio beacon in range
Solution: A previous user may have programmed the GPS to search for one particular radio signal, but you are now out of range. If this is the case, you can program the GPS to search for any beacon that may be in range. See
"c" below for instructions on how to program the GPS to receive any beacon.b. radio beacon blocked by topography (deep canyon, perhaps)
Solution: If you are in severe topography, the radio beacon may become sufficiently degraded so that the receiver can no longer detect it. You have 2 options at this point; 1) acquire the GPS data without the beacon (you can differentially correct the data later by obtaining the differential corrections from a base station), or 2) move out of the steep topography (if appropriate).
c. the receiver is not configured properly
Solution: The datalogger may not be properly configured to acquire the beacon data. To check, use the arrow keys to highlight the "Configuration" area in the main menu (then press the "Enter" key). Next highlight the "Communication Options" area (hit enter), then highlight "Real Time Input" and make sure the following are configured properly
Radio >Custom
Baud Rate>9600
Data Bits>8
Stop Bits>1
Parity>None
Station>Any (this is the critical setting if you can't pick up a beacon. If you know the frequencies of other nearby beacons, you can type those in and try them as well)
Age Limit>20 s (you can play around with this setting, but if you're not receiving a beacon it probably won't help.
Below: Bottom area of datalogger showing low battery state (far left), beacon reception signal (second from left), icon showing the reception from 5 satellites (third from left) and a PDOP reading of 6.4 (explained later).
3. Number of satellites (Third from Left)
The number in the center of the icon refers to the number of satellites that the receiver is obtaining data from. Below, the receiver is obtaining data from 6 satellites. Four satellites are required for GPS data, and typically 5 are necessary. More satellites will generally provide the best data. Note that in the photo below that no beacon is detected (beacon icon is not evident), and that 6 satellites are detected.
4. Dilution of Precision (PDOP Reading (5.1) near the center of the status line above)
This number reflects how "good" or precise you can expect your position data to be. Dilution of Precision is a function of the geometry of the receiver relative to satellites and obstacles. High PDOP readings (greater than 10.0) reflect relatively poor data, perhaps because of too few satellites, satellites that are too low on the horizon (signal is degraded through the atmosphere, or obstacles (trees, topography) interfering with the signal.
You can program the datalogger to record the PDOP readings with the position data. Choose "Configuration" from the Main Menu, then "Logging Options". Now locate the line that reads "Log DOP Data" and make sure that "Yes" appears next to it. This allows you to use Pathfinder Office once you return to the lab to remove any "poor" data points that result from high PDOP readings. You can also set a PDOP
"mask" that will filter out data that have too high of a PDOP reading. To set the PDOP mask, choose "Configuration" from the Main Menu, then "Rover Options", then "Position Filters", then "PDOP Mask". You can then type in a value that will filter out data with PDOP values above your typed value.