RTK GNSS for Mining Survey: Face Mapping, Blast Holes & Stockpiles

The modern RTK mine survey discipline encompasses the entirety of open-pit surface operations. Key applications include:

• Open-pit face mapping and progressive bench surveys for volume reconciliation.
• High-speed blast hole setting-out across expansive drill patterns.
• Routine stockpile volume measurements and toe-and-crest delineations.
• Haul road alignment, gradient checking, and ongoing subsidence monitoring.
• Infrastructure as-built surveys, including crusher pads, overland conveyor routes, and tailings dam embankments.

RTK has replaced the total station for the majority of open pit survey GNSS work. The reasons are operational: RTK offers faster acquisition times, requires only a single operator, and eliminates line-of-sight constraints across wide, undulating pit floors. However, the total station remains necessary for specific use cases, primarily underground control extension and high-precision tunnel alignment where GNSS satellite geometry is absent.

Implementing RTK in mining demands hardware engineered for distinct environmental challenges. Receivers must boast an IP67 rating to combat fine mineral dust and mud. An IK08 impact rating is required to survive blast vibrations and field drops. Equipment must maintain operational integrity in high heat (up to +75°C), and operate in remote locations using autonomous base-and-rover configurations without reliance on external CORS infrastructure.

Open-pit face and highwall surveying presents a clear safety challenge in mining geometry. The standard problem is structural: to measure a bench face or highwall accurately, the surveyor traditionally needs to stand at the toe or the crest of the face with a survey pole. This places the surveyor inside an active blast exclusion zone, or at an unstable crest edge, introducing safety risks.

The AP40 Laser+ mining workflow addresses this hazard. Utilising a 120m green laser fired from a safe standpoint situated outside the exclusion zone or back from the crest, the surveyor can measure face positions, toe coordinates, and crest-to-toe slope geometry. This eliminates the need for physical pole access to the face.

The practical standpoint setup is direct: the surveyor establishes a Fixed RTK position at a safe location on the bench above or below the target face. The laser is then aimed at target points across the face, requiring 3 observations per point to calculate precise coordinates via the integrated IMU and laser-ranging algorithms. Typical applications include geotechnical face mapping, blast damage assessment immediately following a blast, establishing slope stability monitoring setups, and conducting progressive pit surveys for volume reconciliation.

Note: For complex operations, the AP80 Pro adds visual measurement capabilities of face surfaces, allowing for detailed geometry capture where multiple face coordinates are required from a single standpoint.

The requirement for blast hole setting-out is defined by tight schedules. Complex blast hole patterns, comprising between 50 and 500 individual holes, must be set out rapidly on a freshly prepared bench. This task must be completed before the drill rig moves into the sector—typically allowing a 2 to 4-hour operational window.

RTK is the standard choice for this workflow. While a traditional total station setup on a mine bench takes 20 to 30 minutes to establish control, an RTK rover achieves a centimetre-accurate Fixed solution in under 30 seconds from any position on the bench, requiring no local instrument setup or backsight procedures.

The workflow involves loading the drill pattern CSV directly into the ApekSurv field software. Surveyors then utilise Augmented Reality (AR) AR stakeout or standard map navigation to locate each hole position, marking it with survey paint or a peg, and logging the as-staked coordinate for blast design reconciliation. The standard accuracy requirement for blast hole setting-out is typically ±50–100mm horizontally, which is within the RTK Fixed capability. The optimal instrument for this task is the AP20 AR, which provides AR stakeout overlays on the controller screen, accelerating navigation across dense drill patterns. A single operator can set out 200 to 400 holes per day on an open bench.

Accurate stockpile volume measurement is necessary for mine site inventory control. The standard mining stockpile survey RTK workflow involves carrying an RTK rover over the stockpile surface at methodical intervals, recording a grid of surface coordinates that are processed into a Digital Terrain Model (DTM) for volumetric calculation within survey software. This reconciliation occurs on a monthly or quarterly basis for ore, waste rock, and tailings stockpiles.

While drone survey photogrammetry offers a faster alternative for massive, open stockpiles, RTK remains vital for specific operational constraints. RTK is utilised for stockpiles situated adjacent to infrastructure, under overland conveyors, or located in active zones where flying a drone poses regulatory or safety risks.

For complex terrain, the AP40 Laser+ is used for measuring inaccessible stockpile faces. Retaining bund walls, steep retaining faces, and stockpile slopes adjacent to active haulage roads can be measured via laser offset from a safe standpoint, ensuring the surveyor does not enter the active machinery zone. Conversely, the APS1 handheld receiver provides a lightweight option (210g) for walking over smaller, accessible stockpile surfaces, reducing operator fatigue during repeated surveys across multiple stockpiles in a single session.

Establishing reliable GNSS control is necessary for GNSS mining Africa and remote site operations. Because cellular networks are often non-existent, mines require self-contained radio transmission. There are two primary base configurations tailored for mining environments:

LIGHTWEIGHT BASE (AP10 OR AP20):
This configuration involves setting up the base on a known mine survey control monument (typically an embedded bolt in bedrock or a concrete monument on stable ground outside the active mining area). The base broadcasts corrections via an internal 2W UHF radio to rovers operating within an 8–15km radius. This is suitable for single-bench or single-pit operations where all work remains within 15km of the base. No internet and no SIM card are required for the correction link.

MAX5 FOR LARGE OR MULTI-PIT OPERATIONS:
For expansive operations, the MAX5 base station is deployed on the central mine survey control monument. The integrated 5W LoRa radio covers a 25km radius. This is sufficient for single-pit operations from one base position, and for multi-pit operations where satellite pits are located within 25km of the central facility. The 8+ hour battery covers a full production shift. An OLED display on the unit confirms satellite tracking and base status without requiring a field controller—meaning the base can be deployed and left unattended while all survey crews work independently across the site.

Accuracy Note: Local base setups yield the same ±8mm Fixed accuracy as CORS-based RTK, provided the base station is established on a correctly coordinated mine control monument.

Scenario 1 — West Africa Gold Mine (No CORS):
In a remote gold operation in West Africa lacking regional CORS infrastructure, a MAX5 base is erected on the central mine control monument. Two survey teams operate simultaneously. Team Alpha uses the AP20 AR for setting out blast holes on the active bench. Simultaneously, Team Beta uses the AP40 Laser+ to map the steep bench face from a stable crest standpoint. Both rovers receive RTK corrections from the single MAX5 via the 5W LoRa protocol. Full Fixed RTK status is maintained throughout the pit. The MAX5's battery covers the full production shift. No cellular data is required, and all spatial data is referenced to the same local mine coordinate system, ensuring accurate volume reconciliation.

Scenario 2 — Open Pit Highwall Survey (Exclusion Zone):
Geotechnical engineers require a survey of a highwall section deemed unsafe. An AP40 Laser+ rover is positioned on a stable crest standpoint 15m back from the edge. Fixed RTK is confirmed via the local MAX5 base transmission. The surveyor fires the green laser down the highwall face, recording points at 3m vertical intervals across the designated face width. Capturing three observations per point ensures strict algorithmic redundancy. The complete face geometry is captured without personnel entering the hazardous exclusion zone. The dataset is exported to geotechnical software for slope stability analysis.

Scenario 3 — Stockpile Volume Survey (Active Operations):
End-of-month reconciliation requires surveying an active ROM stockpile. The lightweight APS1 handheld is carried over the accessible upper stockpile surfaces by one operator, capturing a grid of points. Simultaneously, the AP40 Laser+ is utilised to measure the inaccessible, steep bund wall faces and the lower stockpile slopes that run adjacent to active haulage routes. By taking laser offset shots from secure standpoints, the surveyor avoids the heavy machinery traffic. The combined dataset is imported into civil volume calculation software. The survey programme is completed during a single shift changeover window, ensuring zero disruption to haulage operations.