Photogrammetry: The Complete Guide
Photogrammetry transforms overlapping photographs into accurate 3D models, orthomosaics, and point clouds. This guide covers everything from the underlying principles to practical applications in surveying, construction, and environmental monitoring.
What Is Photogrammetry?
Photogrammetry is the science of making measurements from photographs. By analyzing overlapping images taken from different angles, photogrammetry software reconstructs the 3D geometry of the photographed scene. The process leverages structure-from-motion (SfM) algorithms that identify matching features across images, calculate camera positions, and triangulate 3D point coordinates. The result is a dense point cloud, textured 3D mesh, or georeferenced orthomosaic — depending on the project requirements. Photogrammetry has been used in mapping and surveying since the mid-1800s, but modern drone-based photogrammetry has dramatically expanded its accessibility and applications.
- Structure-from-motion (SfM) algorithms reconstruct 3D geometry from 2D images
- Requires 60-80% image overlap for reliable 3D reconstruction
- Produces point clouds, 3D meshes, orthomosaics, and digital elevation models
- Can use drone-mounted, handheld, or fixed cameras
- Post-processing software: Pix4D, DroneDeploy, Agisoft Metashape, RealityCapture
Drone Photogrammetry vs Ground-Based Photogrammetry
Drone photogrammetry uses cameras mounted on UAVs to capture nadir (downward-facing) and oblique images of terrain, buildings, and infrastructure. It excels at large-area coverage — a single drone flight can map 50-200 acres in one session. Ground-based (close-range) photogrammetry uses handheld or tripod-mounted cameras to photograph objects or building facades at close range, producing higher-resolution models of smaller areas. Drone photogrammetry achieves 1-3cm ground sample distance (GSD) at typical flight altitudes, while ground-based methods can achieve sub-millimeter resolution for detailed architectural documentation.
- Drone: Covers 50-200 acres per flight, 1-3cm GSD typical
- Ground-based: Higher resolution for facades, monuments, and detailed objects
- Drone requires FAA Part 107 certification and airspace authorization
- Both methods benefit from PPK/RTK positioning and ground control points
How Accurate Is Photogrammetry?
Photogrammetry accuracy depends on camera resolution, flight altitude, ground control, and processing parameters. With properly established ground control points (GCPs) and RTK/PPK positioning, drone photogrammetry routinely achieves 1-3cm horizontal and vertical accuracy. For reference, this is sufficient for topographic surveys, construction progress monitoring, and volumetric calculations. Higher accuracy (sub-centimeter) is achievable with lower flight altitudes and higher-resolution cameras. Without GCPs, accuracy degrades to 5-10cm or worse due to GPS positioning errors propagating through the model.
- With GCPs + PPK/RTK: 1-3cm horizontal and vertical accuracy
- Without GCPs: 5-10cm accuracy (GPS-only positioning)
- Ground sample distance (GSD) determines resolution: 1cm/px at 40m altitude with 45MP camera
- Higher overlap (80%+) improves accuracy and reduces gaps
- Camera calibration and lens distortion correction are critical
Photogrammetry Software and Processing
Photogrammetry processing converts raw images into deliverables through a multi-step pipeline: image alignment, dense point cloud generation, mesh creation, texture mapping, and orthomosaic generation. Leading software includes Pix4Dmapper (industry standard for drone surveys), DroneDeploy (cloud-based, user-friendly), Agisoft Metashape (flexible, supports custom workflows), and RealityCapture (fastest processing, excels at large datasets). Processing times vary from minutes (cloud-based) to hours (local processing) depending on dataset size and hardware. Most software can export to industry-standard formats including LAS, OBJ, GeoTIFF, and DXF.
Common Applications
Photogrammetry is used across construction (progress monitoring, volumetric calculations, site surveys), surveying (topographic maps, contour generation, boundary evidence), mining (stockpile volumes, pit mapping, compliance monitoring), agriculture (crop health mapping, drainage analysis), environmental science (erosion monitoring, habitat mapping), and real estate (property marketing, roof inspections). In construction alone, regular drone photogrammetry flights can save thousands per month by catching issues early and providing objective progress documentation.
- Construction: Progress monitoring, earthwork volumes, site documentation
- Surveying: Topographic maps, contour lines, DTMs
- Mining: Stockpile measurement, pit progression, compliance
- Real estate: Property marketing, roof condition assessment
- Infrastructure: Bridge inspections, road surveys, utility corridors
Photogrammetry vs LiDAR: When to Use Each
Photogrammetry and LiDAR are complementary technologies, not competitors. Photogrammetry excels in well-lit outdoor environments, produces photorealistic 3D models with texture, and is more cost-effective for large-area mapping. LiDAR excels in low-light or indoor environments, penetrates vegetation canopy, and captures dense point clouds regardless of surface texture. For construction sites, drone photogrammetry is typically preferred for regular progress documentation, while terrestrial LiDAR is preferred for detailed interior scanning. Many projects combine both technologies — drone photogrammetry for exteriors and LiDAR for interiors.
Key Takeaways
Photogrammetry converts overlapping photos into 3D models, orthomosaics, and point clouds
Drone photogrammetry achieves 1-3cm accuracy with ground control points and PPK/RTK positioning
Ideal for large-area outdoor mapping, progress monitoring, and volumetric calculations
LiDAR is preferred for indoor scanning, vegetation penetration, and low-light conditions
Leading software: Pix4D, DroneDeploy, Agisoft Metashape, RealityCapture
Frequently Asked Questions
How much does drone photogrammetry cost?
Drone photogrammetry typically costs $800-$3,000 per flight session (4-hour minimum engagement), depending on site size and deliverable requirements. Recurring monitoring contracts receive volume pricing. See our drone survey cost guide for detailed pricing by project type.
What is the difference between photogrammetry and LiDAR?
Photogrammetry creates 3D data from photographs using triangulation algorithms. LiDAR uses laser pulses to directly measure distances. Photogrammetry produces photorealistic textured models; LiDAR produces dense geometric point clouds. LiDAR works in darkness and through vegetation; photogrammetry requires ambient light and clear line-of-sight.
How accurate is drone photogrammetry?
With proper ground control points (GCPs) and RTK/PPK positioning, drone photogrammetry achieves 1-3cm horizontal and vertical accuracy. Without GCPs, accuracy degrades to 5-10cm. This is sufficient for most construction, surveying, and mapping applications.
What equipment is needed for drone photogrammetry?
A photogrammetry-capable drone (DJI M4E, DJI Mavic 3 Enterprise), a high-resolution camera (DJI Zenmuse P1 for survey-grade work), RTK/PPK GNSS capability, ground control points (GCPs), and processing software (Pix4D, DroneDeploy, or Agisoft Metashape). FAA Part 107 certification is required for commercial operators.
Can photogrammetry be used for interior spaces?
Ground-based photogrammetry can document interior spaces, but it requires careful lighting control and dense image capture. For interior documentation, terrestrial laser scanning (3D laser scanning) is generally preferred because it works in any lighting condition and produces more uniformly dense point clouds.
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