1. Why your processing workflow determines whether the field data was worth collecting
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A drone survey is only as valuable as the deliverables it produces. You can fly a perfect mission — RTK fixed throughout, 80% overlap, ideal GSD — and still deliver unusable data if the processing workflow is wrong. The alignment settings, the camera optimisation parameters, the depth filtering choice, the CRS configuration — each of these decisions affects the accuracy of the final orthomosaic, DEM, and point cloud. Get any of them wrong and the checkpoint residuals will tell the story before the client does.
This matters commercially because the processing stage is where you create the deliverables that clients actually pay for. The flight is logistics. The processing is the product. For mining clients expecting audit-quality volumetrics, or construction clients comparing your DEM against a design surface, the difference between a disciplined Metashape workflow and a rushed one is the difference between a defensible report and a liability.
Agisoft Metashape Professional is the processing platform I use for every technical deliverable. It handles the full pipeline from RTK/PPK-geotagged image import through to GeoTIFF, LAS, and DXF export. It runs offline — critical for processing in the field on a laptop when internet access is unreliable — and gives the operator full control over every parameter. That control is the advantage over cloud platforms, but it also means the operator must understand what each setting does and why it matters.
2. The Metashape processing pipeline — six stages, one project file
Every Metashape survey project follows the same six-stage pipeline. The stages are sequential — each depends on the output of the previous one. Understanding this pipeline as a single continuous process, not six separate operations, is what separates a reproducible workflow from ad hoc processing.
The project file (.psx) stores every intermediate result. Save after each major stage. If a dense cloud build fails or a checkpoint review reveals a CRS error, you can revert to the alignment stage and reprocess without re-importing images. This is one of Metashape’s structural advantages over platforms that run the full pipeline as a single black-box operation.
3. Project setup and image import
3.1 Project creation and folder structure
File → New. Save immediately to a dedicated folder named with the date, site, and client: 2026-04-15_Omai_StockpileSurvey. Consistent naming is not optional — when you have 40 projects across repeat-survey clients, searchability is what keeps the archive usable.
Keep the Metashape project file (.psx) and its associated data folder in the same parent directory as the source images. Do not move images after import — Metashape stores relative paths and will lose the image links.
3.2 Importing images — the two PPK paths
There are two routes for getting PPK-corrected geotags into Metashape, and which one you use depends on the job.
Path A: PPK in DJI Terra first, then import corrected images to Metashape. This is the faster route for straightforward jobs. Run Local PPK in DJI Terra — load the PPKRAW.bin and base station DAT file, enter base coordinates, calculate. Terra overwrites the EXIF geotags with corrected positions. Import the corrected images into Metashape via Workflow → Add Photos. The geotags are already PPK-corrected; Metashape reads them directly.
Path B: Use Metashape’s GNSS/INS processing tools. For complex jobs where you need finer control over the correction process, or when working with third-party base station RINEX data that Terra does not accept natively, import the raw-geotagged images into Metashape and use Tools → GNSS/INS Offset to apply corrections within the Metashape environment. This path keeps the entire workflow inside one application.
For RTK missions where the flight log shows uninterrupted Fixed solution, import the images directly — the RTK-corrected geotags in the EXIF are already centimetre-accurate.
Before importing any images, go to Tools → Preferences → Advanced and enable ‘Load camera location accuracy from XMP meta data’. Without this, Metashape assigns a default accuracy of 10 m to all camera positions — effectively discarding the precision of your RTK/PPK measurements. The alignment will still run, but the georeferencing quality will be dramatically degraded.
3.3 Setting the coordinate reference system
In the Reference pane, set the CRS to WGS84 / UTM Zone 21N (EPSG:32621) for all Guyana work. Verify that camera positions display correctly on the map view after import. If positions cluster at the origin or scatter randomly, the CRS is wrong or the geotags did not import correctly — fix this before proceeding.
If XMP import is enabled, Metashape reads accuracy values from the image metadata automatically. If not, set manually:
RTK Fixed: Horizontal 2 cm, Vertical 3 cm
PPK Fixed: Horizontal 2 cm, Vertical 3 cm
RTK Float / Standalone GPS: Horizontal 500 cm, Vertical 500 cm (or exclude these images)
These values tell Metashape how much to weight the geotags during bundle adjustment. Too loose and the model drifts. Too tight and internal distortions are suppressed rather than resolved.
4. Photo alignment — settings, thresholds, and what to do when it fails
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Workflow → Align Photos. This is the most consequential step in the pipeline. Alignment determines camera positions, orientations, and the initial tie point cloud. Everything downstream — dense cloud, DEM, orthomosaic — inherits whatever errors exist in the alignment.
- Accuracy: High for standard production jobs (300–500 images). Use Highest for small, high-detail projects under 200 images where processing time is not a constraint. For large-area surveys exceeding 800 images, Medium is acceptable to manage processing time — the accuracy trade-off is minimal for broad-area mapping.
- Generic Preselection: Enabled. This groups image pairs by approximate position before feature matching, dramatically reducing processing time on large datasets.
- Reference Preselection: Source. This uses the RTK/PPK geotags to pre-filter which images are compared, which is critical for georeferenced datasets.
- Key Point Limit: 40,000 (default). Increase to 60,000 for complex terrain with high surface variability.
- Tie Point Limit: 4,000 (default). Sufficient for most survey work.
- Adaptive Camera Model Fitting: Enabled. Allows Metashape to select the appropriate lens distortion parameters during alignment rather than requiring manual specification.
4.1 Alignment success threshold
Target: ≥95% of images aligned. Below 95%, inspect the unaligned images — they are usually caused by motion blur, insufficient overlap at mission edges, or images captured during turns. Below 90% alignment, the dataset has a structural problem: either the overlap was insufficient, the geotags are corrupted, or lighting conditions caused widespread feature-matching failure.
| Alignment rate | Assessment | Action |
|---|---|---|
| ≥98% | Excellent — proceed | Review unaligned images but no intervention needed |
| 95–97% | Good — proceed with inspection | Disable unaligned images; verify they are not over critical areas |
| 90–94% | Marginal — investigate | Check for systematic cause (blur, shadow bands, overlap gaps) |
| <90% | Failed — do not proceed | Diagnose root cause before reprocessing or re-flying |
4.2 Tropical lighting and alignment quality
In Guyana, the equatorial sun at midday produces harsh overhead light that eliminates surface texture on flat, light-coloured materials — sand, concrete, laterite. This directly reduces tie point density over those surfaces, which in turn creates weak areas in the alignment where the dense cloud will have holes. Fly at 07:00–09:00 or 15:00–17:00 to get raking light that reveals surface texture. If you must process a midday dataset, expect lower tie point density over low-contrast surfaces and inspect the sparse cloud carefully before proceeding to dense cloud.
5. GCP and checkpoint integration
Even with RTK/PPK geotags delivering centimetre-accurate camera positions, GCPs and checkpoints serve distinct and non-redundant functions. GCPs constrain the model to ground truth. Checkpoints validate the accuracy independently. You can skip GCPs on RTK/PPK jobs if the geotag quality is confirmed — but you should never skip checkpoints. Checkpoints are what allow you to write an accuracy statement in the client report.
5.1 Importing and marking GCPs
- Tools → Import Reference. Load GCP coordinates from CSV (columns: Label, X, Y, Z). Set delimiter, CRS, and column mapping.
- For each GCP marker, right-click in the Reference pane → Filter Photos by Marker. Metashape displays the images where the marker should be visible based on position.
- Mark each GCP in a minimum of 4–5 images. Place the marker precisely at the centre of the ground target. Subpixel accuracy matters — zoom in fully before placing.
- After marking all GCPs, run Tools → Optimize Cameras. Enable all standard parameters: f, cx, cy, k1, k2, k3, p1, p2. For DJI M4E data, Agisoft recommends excluding k4 as it can introduce instability. Enable ‘Fit additional corrections’ if checkpoint residuals are not meeting target.
- Review the Reference pane → Errors tab. GCP residuals should be below 2 cm horizontal and 3 cm vertical. If any GCP shows residuals above 5 cm, recheck the marking in all images.
5.2 Setting checkpoints
Checkpoints are GCPs that are excluded from the optimisation — they provide an independent accuracy assessment. In the Reference pane, right-click a marker and uncheck the ‘Control’ checkbox. That marker becomes a checkpoint: Metashape reports its residual error but does not use its coordinates to constrain the model.
Minimum standard: 2 checkpoints per survey area, at different elevations and positions. For mining audit-quality work, 3–5 checkpoints distributed across the site.
6. Dense cloud generation
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Workflow → Build Point Cloud (Metashape 2.x) or Build Dense Cloud (earlier versions). This step generates the full 3D surface reconstruction from the aligned imagery. It is the most computationally intensive stage and the one most affected by GPU performance.
- Quality: High. This is the production default. Ultra High doubles processing time for a marginal improvement in point density that is rarely necessary for survey deliverables. Medium is acceptable for fast-turnaround reconnaissance but does not meet the standard for volumetric or earthworks deliverables.
- Depth Filtering: Moderate. This balances noise removal with detail preservation. Mild retains more surface detail but also more noise — useful for complex structures but not standard for mapping. Aggressive removes too much legitimate surface variation for survey work.
- Calculate Point Confidence: Enable. This allows you to filter low-confidence points later if needed.
6.1 GPU acceleration
Go to Tools → Preferences → GPU. Enable all available NVIDIA GPUs. Dense cloud generation on an NVIDIA RTX card processes a 300–500 image dataset in 30–60 minutes at High quality. Without GPU acceleration, the same dataset can take 3–5 hours on CPU alone. If you are processing in the field on a laptop, this is the difference between delivering same-day results and telling the client to wait.
6.2 Inspecting for holes and artefacts
After the dense cloud builds, inspect it visually before proceeding. Rotate the 3D view and look for:
- Holes over smooth, reflective, or dark surfaces — common on wet laterite, standing water, polished metal roofing, and fresh asphalt. These areas lack texture for stereo matching.
- Canopy edge artefacts — in Guyana interior operations where forest clearings border the survey area, the transition from canopy to open ground produces noisy reconstruction at the tree line. Crop the dense cloud to exclude non-essential canopy areas.
- Noise clusters above the ground surface — caused by birds in flight, dust, or moving vehicles during the mission. Delete these manually with the selection tools before building the DEM.
7. DEM and orthomosaic generation
7.1 Building the DEM
- Workflow → Build DEM. Source: Dense Cloud (not Sparse Cloud or Mesh).
- Interpolation: Enabled. This fills small gaps in the dense cloud with interpolated elevation values. Disable only if you need the gaps preserved for analysis.
- CRS: WGS84 / UTM Zone 21N (must match the project CRS).
- Resolution: Leave at default (derived from dense cloud density). For a typical 2.2 cm/px GSD dataset, the DEM resolution will be approximately 4–5 cm/px.
7.2 Building the orthomosaic
- Workflow → Build Orthomosaic. Surface: DEM (uses the DEM you just built as the projection surface).
- Blending Mode: Mosaic. This produces the sharpest result for survey work. Average blending softens detail. Disabled shows individual image boundaries — useful for debugging but not for deliverables.
- Enable Hole Filling: Yes. Small gaps in the DEM coverage are filled with data from adjacent images.
- Pixel size: Leave at default (matches GSD).
Processing time for the DEM and orthomosaic together is typically 10–20 minutes for a 300–500 image project on an NVIDIA GPU workstation. These are the two primary visual deliverables for most clients.
For standard survey deliverables (volumetrics, earthworks, topographic mapping), the DEM is the correct product. Build a 3D mesh only if the client requires a textured 3D model for visualisation, or if you are surveying structures with vertical surfaces that a 2.5D DEM cannot represent.
If you need both, build the mesh from the dense cloud (Workflow → Build Mesh, Source: Dense Cloud, Face Count: High), then build the DEM from the mesh. This pipeline produces a smoother DEM in areas with complex geometry.
8. Accuracy verification — checkpoint residuals and quality metrics
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This is the step that separates a professional survey from a pretty picture. Before exporting anything, verify the accuracy of your reconstruction against the independent checkpoints collected in the field.
8.1 Checking residuals
Open the Reference pane. The Errors column shows the difference between the surveyed checkpoint position and the position predicted by the Metashape model. Review both the per-checkpoint errors and the summary RMSE.
| Metric | Target | Action if exceeded |
|---|---|---|
| Checkpoint H RMSE | ≤3 cm | Recheck GCP marking; re-optimise cameras; verify CRS consistency |
| Checkpoint V RMSE | ≤5 cm | Check for DJI ellipsoidal height issues; verify base station coordinates |
| Individual checkpoint >8 cm | None should exceed | Recheck that specific checkpoint — possible marking error or field measurement issue |
| Reprojection error | ≤1.0 px (mean) | If above 1.5 px: alignment has quality issues — review tie points |
| Camera location RMSE | ≤3 cm H, ≤5 cm V | Expected for RTK/PPK data — higher values indicate geotag or CRS problems |
8.2 What triggers a reprocess
If checkpoint residuals exceed the targets above, do not export the deliverables. Work backwards through the pipeline:
- First: verify the checkpoint was measured correctly in the field and marked correctly in Metashape.
- Second: re-run Optimize Cameras with additional parameters (enable ‘Fit additional corrections’).
- Third: if the mission had RTK float periods, reprocess the geotags via PPK and re-import.
- Fourth: if residuals persist, add GCPs to constrain the model and re-optimise.
- Last resort: re-fly the mission.
If you have no checkpoints, you have no independent accuracy evidence. The alignment RMSE and camera location errors are internal metrics — they show internal consistency, not absolute accuracy. A mining auditor or construction engineer will ask for checkpoint residuals. If you cannot provide them, the report is not defensible.
9. Export and deliverable packaging
9.1 Orthomosaic export
File → Export → Export Orthomosaic. Format: GeoTIFF. CRS: WGS84 / UTM Zone 21N. Compression: LZW (lossless, reduces file size by approximately 40–60%). Enable ‘Write World File’ if the client’s GIS software requires a .tfw sidecar. For very large sites, enable tiling to produce manageable file sizes.
9.2 DEM export
File → Export → Export DEM. Format: GeoTIFF. CRS: same as orthomosaic. This is the elevation dataset used for volumetric calculations, contour generation, and cut/fill analysis. No-data value: –32767 (standard for GIS compatibility).
9.3 Point cloud export
File → Export → Export Point Cloud. Format: LAS (standard) or LAZ (compressed — approximately 10× smaller). CRS: same as above. Enable colour export if the client requires a colourised point cloud for visualisation. Include confidence values if calculated during dense cloud generation.
9.4 Contour export
For clients who require contour plans: Tools → Generate Contours. Interval: 0.5 m or 1.0 m depending on client specification. Export as DXF or Shapefile. Contours are derived from the DEM, so their accuracy inherits the DEM quality.
9.5 Metashape processing report
File → Export → Generate Report. This produces a PDF containing survey metadata, camera positions, GCP/checkpoint residuals, overlap analysis, DEM preview, and orthomosaic preview. Include this in every client deliverable package — it is the technical documentation that supports the accuracy claims in your report.
Orthomosaic: GeoTIFF + .tfw world file
DEM: GeoTIFF
Point cloud: LAS or LAZ (if requested)
Contours: DXF or Shapefile at specified interval
Processing report: Metashape PDF report
Accuracy statement: Checkpoint residual table with H and V RMSE
Metadata: CRS, datum, geoid model, survey date, equipment, software version
File naming convention: [Client]_[Site]_[Date]_[Deliverable].[ext]
10. Settings reference table — the production defaults
This table documents every Metashape setting used in the production workflow. Bookmark it. These are not Agisoft defaults — they are the settings I use on commercial survey jobs after testing alternatives across dozens of projects in mining, construction, and O&G.
| Setting | Production value | When to change |
|---|---|---|
| Alignment Accuracy | High | Highest for <200 images; Medium for >800 images |
| Generic Preselection | Enabled | Never disable for georeferenced datasets |
| Reference Preselection | Source | Use ‘Estimated’ only if geotags are absent |
| Key Point Limit | 40,000 | Increase to 60,000 for complex terrain |
| Tie Point Limit | 4,000 | Increase to 10,000 for oblique imagery |
| Adaptive Camera Model Fitting | Enabled | Disable only if using a known calibration file |
| Dense Cloud Quality | High | Ultra High for small, high-detail projects only |
| Depth Filtering | Moderate | Mild for structures; Aggressive for flat terrain with vegetation noise |
| Point Confidence | Enabled | Always enable — no performance penalty |
| DEM Source | Dense Cloud | Use Mesh source only for 3D structure surveys |
| DEM Interpolation | Enabled | Disable only for gap analysis workflows |
| Orthomosaic Surface | DEM | Use Mesh for oblique/facade work |
| Orthomosaic Blending | Mosaic | Average for aesthetic rendering; Disabled for debugging |
| Optimize Cameras — k4 | Disabled for M4E | Enable for other camera platforms; per Agisoft guidance |
| Optimize Cameras — Additional Corrections | Disabled (default) | Enable if checkpoint residuals are not meeting target |
| Export CRS | WGS84 / UTM 21N | Match to client specification if different |
| GeoTIFF Compression | LZW | None for maximum compatibility with legacy software |
| GPU Acceleration | All available | Disable if encountering GPU memory errors on large projects |
11. Common processing errors and how to fix them
| Error | Consequence | Fix |
|---|---|---|
| XMP accuracy not loaded | Metashape ignores RTK/PPK precision; model drifts | Enable in Preferences → Advanced before import; re-add photos if missed |
| Alignment below 90% | Incomplete coverage; gaps in dense cloud and ortho | Check for blur, overlap gaps, or geotag corruption; re-fly if structural |
| Dense cloud holes over flat surfaces | DEM interpolates across gap; volume errors | Increase overlap; fly with raking light; use Mild depth filtering |
| Checkpoint V residual >8 cm | Vertical accuracy insufficient for volumetrics | Verify base station coordinates; reprocess with PPK; add GCPs |
| CRS mismatch between GCPs and project | All markers show large systematic offset | Verify EPSG codes match; check for WGS84 vs local datum confusion |
| Orthomosaic seam lines visible | Unprofessional deliverable; client complaints | Switch to Mosaic blending; check for exposure variation between flight lines |
| Canopy noise at clearing edges | DEM elevation errors at site boundary | Crop dense cloud to exclude canopy; classify points if needed |
| Project file corrupted after crash | Loss of all processing work | Save after every major stage; keep backups of .psx and data folder |