If you have decided to use a local base station, this document explains the important characteristics to consider.

What to Look for When Purchasing or Renting a Base Station 

Using a static base station with the qCam has become one of the most practical ways for field crews to achieve survey-grade accuracy without relying on a nearby CORS station or a rented local base network. But the quality of your final solution is only as good as the raw observation data your base station collects. Whether you're buying equipment for your organization or renting for a single project, the following factors will directly affect the accuracy, reliability, and convergence time of your post-processed results.

1. Multi-Frequency, Multi-Constellation Tracking

For base stations, dual-frequency (L1/L2 or L1/L5) tracking is non-negotiable. Dual-frequency receivers allow the processing software to model and remove ionospheric delay directly from the observations, which is one of the largest error sources in single-point positioning. Single-frequency receivers can still be corrected using external ionospheric models, but the resulting accuracy is noticeably worse and convergence takes much longer.

Beyond frequency, look for multi-constellation support (GPS, GLONASS, Galileo, and BeiDou) at minimum. More visible satellites mean:

• Faster ambiguity resolution and convergence
• Better geometry (lower PDOP) in obstructed or urban environments
• More redundancy if one constellation experiences an outage or degraded signal

Many free online PPP services (NRCan's CSRS-PPP, AUSPOS, APPS) support multi-GNSS processing now, but confirm compatibility before committing to a receiver — some services still process GPS-only or GPS+GLONASS observations most reliably.

2. Use a Proper Survey-Grade Antenna (Not a Consumer GPS Antenna)

The antenna is just as important as the receiver itself. Here's why: every GPS antenna has a tiny, built-in quirk — the exact point where it "hears" the satellite signal isn't perfectly at its physical center. Cheap antennas don't have this quirk precisely measured, which means your final position can be off by a small amount (usually in the vertical/height measurement) without you ever knowing it.

Survey-grade antennas come with a "calibration report" that tells the processing software exactly where that true signal point is, down to the millimeter. This lets the software correct for it automatically.

What this means for you:

• If you're renting equipment, ask the rental company whether the antenna is a recognized, calibrated survey model. Most professional processing tools (free or paid) keep a built-in list of known antennas — if your antenna isn't on that list, you'll get a small but avoidable error in your results, especially in elevation.
• Look for antennas designed specifically for surveying, not general navigation or consumer GPS units.

Bonus tip: if you're setting up near metal roofs, vehicles, or water, choose an antenna designed to block "bounced" signals (sometimes called a choke-ring or ground-plane antenna). GPS signals can bounce off shiny/reflective surfaces before reaching your antenna, which confuses the measurement — a better antenna design filters that noise out, especially important for long, all-day setups.

3. Data Logging Rate, Format, and Session Length

• Logging interval: 1 Hz or 15-second epochs are standard; you will need to confirm the receiver can log at a 1 second rate that is needed for the qCam compatibility.
• Output format: Native RINEX 3.x output (or software that converts cleanly to it) saves significant post-processing headaches. Some receivers only output proprietary binary formats requiring third-party conversion tools, which can introduce data loss or corrupted headers.

4. Stable, Repeatable Mounting

Since you have no baseline to a known point, all your accuracy depends on the base station's own position being solved precisely — which means the antenna cannot move or tilt during the occupation. Look for:

• A forced-centering tribrach or fixed pillar mount for repeat occupations of the same point
• A tripod rated for extended outdoor exposure (wind loading is a common source of subtle antenna tilt)
• Accurate antenna height measurement tools (fixed-height poles reduce operator error versus slant-height tape measurements)

5. Sky Visibility and Multipath Environment

Base stations are more sensitive to a clean sky view than relative/RTK positioning, since there's no nearby reference station to help cancel local atmospheric and multipath errors. When selecting a base location:

• Avoid canopy, buildings, or structures within roughly a 10–15° elevation mask
• Keep the antenna away from large reflective surfaces
• If renting equipment for a specific job site, scout the site (or use satellite imagery) beforehand to confirm a viable base location exists — this affects your choice of tripod height and cable length as well

6. Power and Data Storage for Long Occupations

Base station sessions often run far longer than RTK setups. Confirm:

• Battery life covers your planned occupation with margin (external battery packs or solar trickle chargers for 24-hour sessions)
• Internal storage capacity at your chosen logging rate —half a day at 1 second intervals across multiple constellations can be a surprisingly large file
• Whether the receiver supports remote monitoring (cellular/Wi-Fi status checks), which matters more for unattended long-duration times

7. Compatibility with Your PPP Processing Workflow

Finally, confirm the receiver's output plays well with your intended processing path:

• Free government services (CSRS-PPP, AUSPOS, APPS, OPUS for the US NGS network) each have their own accepted formats, minimum occupation times, and supported constellations — check compatibility before renting or buying.
• Commercial software (Trimble Business Center, Waypoint/NovAtel Inertial Explorer, RTKLIB) offers more control but requires more expertise; confirm your receiver's raw data format is supported natively or via a documented converter.
• If your workflow includes PPP-AR (ambiguity resolution) for faster convergence, verify the service or software you're using actually supports it — not all do, and support varies by constellation.

Buy vs. Rent — Quick Decision Factors

If renting, always ask the vendor directly for the antenna's calibration status, supported logging rates/formats, and battery/storage specs for your planned session length — these are the details that most often get glossed over in a generic rental listing but have the biggest impact on your final accuracy.