Quick Answer
How do you set up a base and rover RTK GPS system?
Set the base receiver on a known control point, enter coordinates and antenna height, start broadcasting corrections via UHF radio or cellular NTRIP, then power up the rover and confirm RTK Fixed status before beginning stakeout. Always verify rover accuracy against a second known control point before trusting positions for construction layout.
How to Set Up Base and Rover RTK GPS for Construction
Applies to: Trimble R10/R12i, Topcon HiPer HR/VR, Leica GS18 T, Spectra Geospatial SP80
A base-and-rover RTK GPS system is the standard setup for construction stakeout and topographic survey. The base provides the correction reference that transforms each rover from meter-level GPS accuracy to centimeter-level RTK accuracy. Getting the base set up correctly takes 10-15 minutes; doing it wrong costs hours of rework. This guide covers the complete setup workflow for a two-person crew using their own base station rather than a network correction service.
Step 1: Set Up the Base Station
Select a control point with clear sky view (avoid locations under trees, near tall buildings, or in radio shadow for your working area). Set up a tripod over the control monument and attach the tribrach. Mount the GNSS receiver and center it precisely over the point using the optical or laser plummet. For base station work, aim for centering within 2-3mm of the monument center.
Level the tribrach using the footscrews until the electronic bubble is centered. Measure the vertical height from the monument top to the antenna reference point (ARP) — typically the bottom edge of the receiver housing or a labeled reference mark. Record antenna height to the nearest millimeter. An error of 10mm in antenna height shifts all rover elevations by exactly 10mm.
Step 2: Configure Base Coordinates
Connect the field controller to the base receiver via Bluetooth. Open the survey software and start a new base setup. Select "Known Point" and enter the control point ID, northing, easting, and elevation in the project coordinate system. Confirm the coordinate system and datum — NAD83(2011), NAD83 State Plane, WGS84, or a localized site calibration system depending on the project.
Enter the measured antenna height. Double-check the antenna height entry before confirming — this is the single most common setup error on construction sites. Start the base. Most systems will show a satellite count and PDOP as the receiver tracks satellites; wait for the satellite count to stabilize (typically 8+ satellites) before proceeding.
Step 3: Configure the Correction Broadcast
For UHF radio: confirm the radio frequency and correction format (RTCM 3.2 or CMR+ are most common) match your rover configuration. The base radio transmit light should flash at the configured broadcast interval. Extend the radio antenna fully and orient it vertically for maximum range. Typical UHF range is 3-8 km in open terrain.
For cellular NTRIP: configure the base to broadcast to an NTRIP caster using your account credentials. Create or select a mount point name that rovers will connect to. Cellular broadcast eliminates radio range limits but requires cell coverage across the site.
Step 4: Set Up the Rover
Mount the GNSS rover on a range pole at the correct pole height. Extend the pole to the standard height used in the project (most commonly 2.0m) and confirm the height is entered correctly in the rover software — pole height errors shift all elevations by the height error amount. Connect the field controller to the rover via Bluetooth.
Start a rover survey in the controller software, selecting the same project and coordinate system as the base. Configure the rover to receive corrections on the same frequency/protocol as the base broadcast. The rover will begin tracking satellites and searching for the correction signal. RTK Fixed status typically appears in 30-90 seconds of good sky view.
Step 5: Verify on a Known Control Point
Before beginning any stakeout or data collection, occupy a second known control point that was not used as the base. Compare the rover's reported coordinates against the published control point coordinates. Acceptable residuals: under 0.025m horizontal, under 0.050m vertical for most construction stakeout work. Tighter tolerances (0.010m horizontal) apply to structural layout.
If residuals exceed tolerance, recheck base antenna height, base coordinates, and coordinate system before proceeding. Do not begin layout work until the check shot passes — errors that propagate from an incorrect base position affect every point set on the job.
Frequently Asked Questions
What is RTK Fixed status and why does it matter?
RTK Fixed means the receiver has resolved carrier phase ambiguities and is computing positions at centimeter-level accuracy (typically +/-10-20mm). Float status means ambiguities are not fully resolved and accuracy is sub-decimeter but not centimeter — not suitable for construction stakeout. Always wait for Fixed status before beginning layout.
How do I know if my base and rover are using the same coordinate system?
Check shot verification tells you. If your rover reads within 25mm of a known point with published coordinates, the coordinate system is consistent. Systematic errors of 0.5m+ indicate a datum or projection mismatch — typically WGS84 vs. NAD83 or a wrong State Plane zone.
Can one rover work with multiple base stations?
A rover listens to one correction source at a time. In the field, if the primary base signal is lost, the rover will lose RTK Fixed and degrade to Float. Some crews deploy two base stations on large sites and configure rovers to switch between them, though this requires careful coordinate system management to ensure both bases produce consistent results.
What causes the rover to lose RTK Fixed during work?
Common causes: moving out of base radio range, obstructions blocking the radio or cellular link, sudden sky obstruction reducing satellite count below threshold, and multipath from large metal structures nearby. When Fixed is lost, wait for re-initialization before continuing high-accuracy work.
Document every base setup, control point, antenna height, and check shot in Gradelog — automatic GNSS session logging built for construction crews. Free to start at gradelog.com.
