RTK Setup Guide


The following is a concise step-by-step guide to setting up the Trimble equipment for RTK surveying. It does not cover the theory of operation; these instructions are much more useful after an introduction to the system.

    Base Station Setup - do this first
  1. GPS Receiver
    1. Setup GPS antenna tripod and tribrach; insure that the optical plummet is aligned with the base station benchmark, and that the tribrach is level.
    2. Attach GPS satellite antenna ("GPS antenna") to the tribrach via the brass adapter. Attach GPS antenna cable (yellow 3-shell [large] Lemo to right-angle coaxial connector) to the antenna.
    3. Connect the base station battery (use the attached cable) to port #2 of the GPS receiver.
    4. Connect the GPS antenna cable to the receiver's antenna port (labelled, and the only port that fits).
    5. Connect the data collector I/O cable to receiver port #1; the cable is black, with 0-shell [small] Lemo connectors on each end. One end is straight, the other a right-angle. Connect the right angle connector to the receiver.
    6. Place the receiver inside the transport case (for weatherproofing). Be sure not the have any sharp bends in the cables, and do not clamp the lid on any cables.
    7. Connect the data collector to the other end of the data collector I/O cable connected to receiver port #1.
    8. Turn on the data collector and GPS receiver by pressing the green power button on the data collector.
    9. Measure the GPS antenna height using the Height Rod. Measure at 3 points (120 degrees apart). Always measure from the benchmark stamp to the bottom edge of the groundplane, inside a notch. Record the three measurements; if they are different by more than a few mm, check level and centering of the GPS antenna. Average the readings and enter the average into the data collector when prompted; either enter in meters, or type in the number followed by the unit (e.g. cm for centimeters). Check that the measurement type is set correctly.
  2. Base radio
    1. Choose a location more than 10' from the GPS antenna. Do not choose a location near trees, cars, buildings, etc.
    2. Setup tripod with tribrach, levelling at the highest possible stable height.
    3. Attach the radio antenna cable to the tribrach with the brass adapter. If possible, use 2 pieces of the radio mast to increase the height of the radio antenna; save the 3rd piece for the Rover system, if not using the 2m rangepole.
    4. Attach the radio antenna, with tip (0dB or 5dB), to the radio antenna cable.
    5. Put the base radio near the radio antenna, preferably in a sheltered location. At the very least, place the cooling fan downhill without restricting airflow.
    6. Connect the radio antenna cable to the radio; there is only port that will work, and it is labelled.
    7. Connect the power cable to the radio; there is only one port that will work, and it is labelled. Be sure to align the red dot and mark before pushing with any force.
    8. Connect the donut lugs on the power cable to the battery; red to positive. DO NOT CONNECT WITH REVERSE POLARITY; the 10A fuse in the cable will blow, and it is possible to damage the radio.
    9. Connect the green ground cable (spade lug to alligator clip) to a real Earth ground. If no metal is readily available, use a piece of metal bar driven into the ground.
    10. Turn on the radio; remove the removable faceplate, and use the black knob. This is also the volume control.
    11. Select a channel that is not in use. Preferably avoid channels 15 and 16, as the FCC has an unusually large number of complaints on these channels. Make sure that the status light is green, indicating the use of Carrier Detect; changing carrier detect requires use of a PC and the COMMSET program.
    12. Once a channel is selected, close the faceplate and note the channel number; this will be needed for the rover.
    13. Connect the base radio data cable (30m flat yellow jacket, 1-shell Lemo [medium] to 0-shell Lemo) to the GPS receiver port #3.
  3. Start the base station measurements
    1. Make sure that the correct Job is selected on the data collector. New Jobs may be defined in the Files mode.
    2. On the hand controller, choose Survey, and then choose the appropriate Survey Style; typically Trimble RTK or a custom style. New styles may be defined at this stage, or in the Survey Styles option in the Configuration mode.
    3. Choose Start base station. Type in the benchmark name, and the position, if known. If no position is known, the Here softkey will use the current GPS position. This is not very accurate, and is not recommended for precision work.
    4. Press the measure softkey, and disconnect the data collector when instructed to do so. Do not turn off the base receiver. Check that the satellite LED (red) is blinking slowly on the GPS receiver, and the transmit light (labelled "TX") on the base radio blinks once per second. This indicates everything is working correctly.
    Rover setup - do this after the base station is running
  1. GPS receiver
    1. Place 2 charged camcorder batteries in the holders at the bottom of the rover backpack.
    2. Connect the battery cables to the batteries, and use the Velcro straps to secure the batteries and cables in place.
    3. Strap receiver into the backpack, upside down. Use the lower set of straps, which have 2 black foam pads underneath.
    4. Connect the battery cables to ports #2 & #3 on the GPS receiver.
    5. Thread the radio antenna cable through a top cable pass-through, and attach the antenna mount to a brass threaded mount on the backpack. (The radio cable is normally left in the backpack, so this step is normally skipped.)
    6. Connect the radio antenna cable to the GPS receiver.
    7. Attach the radio antenna, with the correct tip (0dB or 5dB).
    8. If not using the 2m rangepole, attach the GPS antenna to the 3rd piece of the radio mast, and attach that to the other brass mount on the backpack.
    9. If using the 2m rangepole, attach the antenna to a Quick-Connect shaft, and attach the quick-connect to the assembled rangepole.
    10. Thread the GPS antenna cable through the other top cable pass-through and coil neatly above the receiver. Do not kink the cable. Connect the 3-shell Lemo [large] to the GPS receiver, and the coaxial connector to the antenna.
    11. Connect the data collector I/O cable to receiver port #1.
    12. Thread the data collector I/O cable through the lower pass-through on the same side as the GPS antenna cable. Connect to the data collector.
    13. Tie down loose cables in the pack, and zip it closed.
    14. Put on and adjust the pack for a comfortable fit.
    15. Turn on the data collector (and hence the GPS receiver).
    16. Measure vertical height of the antenna; this is measured to the bottom of the antenna mount, and can be done with the Height Rod. Check that the measurement type is correct.
  2. Start the rover measurements
    1. Make sure that the correct Job is selected on the data collector. New Jobs may be defined in the Files mode.
    2. On the hand controller, choose Survey, and then choose the appropriate Survey Style; typically Trimble RTK or a custom style. New styles may be defined at this stage, or in the Survey Styles option in the Configuration mode. Be sure to choose the same style as for the base station.
    3. Choose Start survey.
    4. Choose Measure Points, Continuous Topo, etc.
    5. When measuring points (of any type), the Rover will attempt to initialize on-the-fly (OTF). This can only be done if 5 or more satellites are visible and tracked by both the rover and base station.
    6. When the radio link is locked, and the receiver has completed the OTF initialization, the status line on the data collector will have estimated uncertainty and "RTK Fixed" displayed. You can know begin measuring points.
    7. If less than 5 satellites are visible, it is possible to initialize on a known point. However, the data quality is liable to be poor due to the low number of satellites. It is often advisable to change locations or try the survey at a later date with more satellites.
    8. For all GPS surveying, try to keep the PDOP < 6.0 - the best yet seen was 1.7 (8 satellites in open terrain), and PDOP tends to average about 3.0 with 5 or more satellites.

Written by Paul Gettings
Last modified