Managing biomass stockpiles — especially irregular, fluffy wood chip piles — is challenging. Traditional ground surveys are slow, unsafe, and often imprecise. Drone-mounted LiDAR, combined with GNSS correction and smart ground control, offers a safer and more efficient solution. But how accurate is it in real-world biomass inventory management?
In this post, we’ll explore what results you can expect using DJI’s Zenmuse L2 LiDAR sensor, paired with D-RTK 3 base station and AeroPoints smart ground control points (GCPs), when measuring wood chip stockpiles.
Why Wood Chip Piles Are Tricky
Wood chip biomass piles are unlike gravel or ore: – Irregular and fluffy: Slopes aren’t clean, and pile tops are uneven. – Low surface texture: Photogrammetry struggles to find enough visual tie points. – Variable density: Wet vs dry chips, compaction, and chip size make bulk density highly unpredictable.
This means surface measurement accuracy is only half the battle — converting to tonnage requires good bulk density data.
The Role of D-RTK 3 and AeroPoints
- D-RTK 3 Base Station: Provides real-time kinematic (RTK) corrections, so every LiDAR scan is geotagged with centimeter-level accuracy.
- AeroPoints: Smart GCPs that log GNSS data independently, later corrected against reference stations. Placed around the pile base, they validate and adjust the LiDAR-derived surface model.
Together, they give you both efficiency (RTK in the air) and ground-truth validation (AeroPoints on the ground).
Expected Accuracy for Biomass Volumes
Let’s run the numbers on a 20,000 m³ wood chip pile:
RTK Only (D-RTK 3)
- Accuracy: ±5%
- Volume error: ±1,000 m³
- Mass error (assuming 300 kg/m³ bulk density): ±300 tonnes
RTK + AeroPoints (Hybrid Workflow)
- Accuracy: ±3%
- Volume error: ±600 m³
- Mass error (at 300 kg/m³ bulk density): ±180 tonnes
Why Density Matters More Than Volume
Even perfect volume calculations won’t solve the variability of wood chip density.
For example: – At 300 kg/m³ bulk density ±20%, the tonnage range for a 20,000 m³ pile is 4,800 – 7,200 tonnes — a 2,400 tonne swing. – By comparison, the volume measurement error (±180 tonnes with AeroPoints) is tiny.
This highlights the importance of regular bulk density sampling or weighbridge correlation.
Best Practices for Biomass Surveys
- Fly with RTK enabled and plan flight paths with full pile coverage.
- Place AeroPoints around the pile base on firm ground, not on the chips themselves.
- Process in DJI Terra, validating pile base elevations with AeroPoints.
- Sample density in the yard or correlate volumes with weighbridge data.
- Repeat consistently — same flight plan, AeroPoint positions, and processing workflow.
The Bottom Line
- RTK alone gives good accuracy (~5% volume error).
- Adding AeroPoints trims this down to ~3%, making results more reliable and audit-ready.
- Bulk density uncertainty dominates — without good density data, tonnage estimates will remain approximate.
In short, drones with LiDAR plus a hybrid RTK + GCP workflow make stockpile measurement safer, faster, and more accurate. For biomass operators, the real win comes from combining these precise volume measurements with reliable bulk density sampling.
Want to try this workflow? Start with your next stockpile survey by adding AeroPoints around the pile base. You’ll quickly see the difference in accuracy and confidence in your biomass inventory reports.