What is the accuracy difference between Fixed and Float RTK?

Fixed RTK typically delivers ±8 mm horizontal and ±15 mm vertical accuracy. Float RTK carries ±300–1000 mm of positioning error depending on baseline length and atmospheric conditions.

Why does my RTK show Fixed but coordinates are still wrong?

Common causes are a datum mismatch (wrong coordinate system), an incorrect geoid model applied to elevation, or an antenna height entry error.

How do I know if multipath is affecting my survey?

Multipath typically shows as unstable repeated measurements — the same physical point measured three times gives results differing by 20–50 mm rather than the expected ±8 mm.

Can I survey during ionospheric storms?

RTK accuracy degrades during geomagnetic storms (Kp index above 5). For precision engineering or cadastral surveys, postpone sessions until the Kp index drops below 3.

What is the maximum reliable CORS baseline for centimetre accuracy?

Most CORS networks guarantee ±10–20 mm horizontal accuracy within 50 km of the nearest reference station. Beyond 70 km, deploy a self‑deployed base station within 15 km of the survey area.

Topographic Survey Equipment: Full RTK Lineup

Topographic Survey Equipment: Full RTK Lineup | APEKS GNSS

1408ch

Full-Constellation Tracking

120°

Calibration-Free IMU Tilt

25 km

MAX5 LoRa Base Range

±8 mm

RTK Fixed Accuracy

Modern topographic mapping demands equipment that handles open desert corridors, forested mountain terrain, and dense urban cores in the same project week. The right instrument depends on terrain, obstruction level, and correction infrastructure — not a single product. APEKS provides a complete RTK ecosystem: first-generation dual-purpose base/rover units, second-generation receivers with integrated laser and vision capabilities, a dedicated long-range base station, and a lightweight handheld — all running ApekSurv field software on the same project file.

The Core Challenges in Topographic Survey

SINGLE-OPERATOR EFFICIENCY ON LARGE SITES

Symptom: Two-person teams are expensive for bulk topographic pickup across large open sites. Single-operator GNSS is theoretically faster but in practice the operator spends as much time levelling the bubble as recording points.

Cause: Standard RTK receivers require the pole to be plumb within a degree for accurate measurement — the operator must stop, check, and level at every point. On uneven terrain this adds 5–10 seconds per point, accumulating to hours on a thousand-point survey.

Fix: APEKS receivers use a 120° calibration-free IMU with no magnetic calibration required. The operator plants the pole tip and records immediately at any angle up to 60° from vertical — no levelling step, no calibration reset. All models from AP10 to AP80 Pro carry this IMU as standard.

GNSS FAILURE UNDER CANOPY AND IN URBAN CANYONS

Symptom: Survey areas include forested sections, steep valleys, or built-up urban blocks where satellite geometry is insufficient for reliable Fixed solution. The GNSS team records what it can and leaves gaps — requiring a second mobilisation with a total station to fill them, doubling cost and creating two datasets to merge in the office.

Cause: RTK requires a minimum number of satellites across multiple constellations to resolve carrier-phase ambiguities. Under dense canopy or surrounded by tall buildings, usable satellite count drops below the threshold for consistent Fixed solution.

Fix: All APEKS receivers track 1408 channels across 7 constellations simultaneously — GPS, GLONASS, BeiDou, Galileo, QZSS, NavIC, SBAS. Full-constellation tracking maximises the usable satellite pool in any obstruction scenario. For points beyond GNSS reach, the AP40 Laser+ measures inaccessible features by laser from a clear vantage point — wall faces, embankment slopes, and features across drainage channels — without a second instrument setup.

REMOTE SITES WITH NO CORS COVERAGE

Symptom: The project is in a remote area — desert infrastructure corridor, highland agricultural survey, or coastal zone — where the nearest CORS reference station is 80+ km away. Single-rover NTRIP is unreliable at this baseline. Accuracy degrades, Fixed drops out, and the team wastes hours troubleshooting a connection that will never be adequate for the site.

Cause: RTK accuracy degrades with baseline length. Beyond 50 km, atmospheric decorrelation prevents reliable Fixed. Beyond 70 km, Fixed resolution is unreliable regardless of receiver quality.

Fix: Deploy APEKS Base+Rover 1+1. Any AP10 or AP20 serves as a lightweight base on a known control point, broadcasting via built-in 2W UHF radio to the rover within 8–15 km. For large project areas, deploy the MAX5 dedicated base station — 5W LoRa radio, 25 km range, 13,200 mAh battery for 8+ hours of continuous operation. No internet, no cellular dependency, no CORS subscription required.

APEKS Solution for Topographic Mapping

OPEN-TERRAIN PICKUP:
AP20 rover or any 2nd Gen receiver with MAX5 base station or CORS connection. 120° IMU single-operator pickup. ApekSurv records point codes, descriptions, and solution quality for every observation — office-ready data from the field. APS1 handheld supports lightweight GIS attribute collection alongside the main topo survey.

MIXED AND OBSTRUCTED TERRAIN:
Full-constellation 1408-channel tracking extends Fixed into light-to-moderate canopy. For inaccessible features — embankment slopes, features across drainage channels, building façades — the AP40 Laser+ measures by laser offset from a clear standpoint up to 120 metres away, without moving the instrument setup.
For inaccessible or hazardous features — live power lines, unstable slopes, or areas with no safe foot access — the AP60 Vision and AP80 Pro support visual measurement via the front-facing camera. The operator shoots a video sweep of the target area; the software automatically extracts stereo photo pairs and derives 3D absolute coordinates for each matched point. The resulting coordinate data carries full 3D positional information and can be imported directly into 3D modelling software. This also complements drone survey — covering blind spots and corners that aerial imagery cannot reach, with data from both sources combined into a single 3D model.

REMOTE SITES:
MAX5 base station on a known control monument. 5W LoRa covers up to 25 km across flat terrain from one base position. 13,200 mAh battery runs a full 8-hour session without external power. Multiple rovers can work simultaneously from the same MAX5 base.

Recommended Equipment for Topographic Survey

Instrument	Generation	Key Specification	Best For
AP10	1st Gen Rover/Base	1408ch, 120° IMU, 2W UHF, IP67/IK08	Entry rover, lightweight base for remote sites
AP20	1st Gen Rover/Base	1408ch, 120° IMU, 2W UHF, IP67/IK08	General rover, base+rover kits, developing markets
AP30 Laser	2nd Gen Laser	1408ch, 30m laser, front: laser aiming, bottom: AR stakeout	Urban topo, short offset measurement
AP40 Laser+	2nd Gen Laser	1408ch, 120m laser, front: laser aiming, bottom: AR stakeout	Infrastructure, slope faces, inaccessible features
AP50 Vision	2nd Gen Vision	1408ch, front: visual survey+3D, bottom: AR stakeout	3D modelling alongside topo pickup
AP60 Vision	2nd Gen Vision	1408ch, front: visual survey+3D, bottom: AR stakeout	High-volume sites, visual measurement
AP80 Pro	2nd Gen Flagship	1408ch, 120m laser, front: laser+visual, bottom: AR stakeout	All terrain, ALL IN ONE
MAX5	Dedicated Base	5W LoRa, 25km, 13200mAh, OLED, no controller	Remote base, desert, offshore, large area
APS1	Handheld RTK	1408ch, 60° IMU, 210g, IP67	GIS collection, asset inventory, light topo support

All instruments run ApekSurv field software. GNSS data from all models is recorded in a single project file format — no post-session conversion or dataset merge required.

COMPLETE RTK ECOSYSTEM. ONE SOFTWARE PLATFORM.

From entry base/rover to flagship all-in-one — APEKS covers every topographic scenario with 1408-channel full-constellation GNSS and 120° calibration-free IMU across the full range.

View APEKS GNSS Receivers →