What is photogrammetry? How it works, aerial vs close-range, and photogrammetry vs lidar
Key takeaways
- Photogrammetry measures 3D geometry by triangulating matching points seen in overlapping photographs.
- Drone photogrammetry accuracy is typically about 1 to 3 times the ground sample distance (GSD) when ground control or RTK/PPK camera positions are used.
- Aerial photogrammetry maps terrain and sites; close-range photogrammetry measures objects, buildings and parts.
- Photogrammetry cannot see through vegetation and struggles on shiny, dark or textureless surfaces, where lidar performs better.
- Ground control points measured with a GNSS RTK receiver are what turn a photo model into survey-grade data.
What is photogrammetry? Definition and meaning
Photogrammetry is the technique of obtaining reliable measurements of physical objects and the environment from photographs. A short photogrammetry definition is: measuring in 3D from 2D images. The word combines the Greek roots for light, drawing and measurement, which is a good summary of the meaning of photogrammetry.
To define photogrammetry in survey terms, it is a method of indirect measurement: you never touch the object; you photograph it from known or computed camera positions and calculate coordinates by triangulation. The American Society for Photogrammetry and Remote Sensing (ASPRS) publishes positional accuracy standards for photogrammetric products, and the discipline has been used for national mapping since the early twentieth century.
Today 3D photogrammetry is mostly digital and highly automated. A drone flies a grid, software matches millions of features across hundreds of images, and the output is a dense point cloud, a textured mesh, a true orthophoto and a digital surface model, often within hours.
How does photogrammetry work step by step?
Photogrammetry works by finding the same feature in at least two, and ideally many, overlapping images, computing where each camera was, and intersecting the viewing rays to place each feature in 3D. Modern software automates this as structure from motion (SfM) followed by dense matching.
- Plan the capture. Choose the ground sample distance (GSD, the ground size of one pixel), flight height and overlap. For drone mapping we typically recommend about 75–80% forward overlap and 65–70% side overlap.
- Set ground control. Mark and survey ground control points (GCPs) and separate check points across the site.
- Capture images. Fly or walk the pattern with fixed focus and consistent exposure; avoid motion blur.
- Feature matching. The software detects keypoints in each image and matches them between images.
- Bundle adjustment. Camera positions, orientations and lens parameters are solved together with the 3D tie points, constrained by GCPs or precise camera positions.
- Dense reconstruction. Pixel-level matching produces a dense point cloud, then a mesh and surface model.
- Products and QA. Generate orthophotos, contours and models, and report errors on independent check points.
GSD drives everything. It equals sensor width × flight height ÷ (focal length × image width). As a rough guide, a typical 20 MP one-inch mapping camera flown at 100 m gives a GSD of about 2.5 to 3 cm.
What are the types of photogrammetry?
The main types of photogrammetry are aerial and close-range, divided by the distance between camera and object, with satellite and terrestrial methods at either end. Each suits different jobs and accuracies.
| Type | Platform | Typical accuracy | Main uses |
|---|---|---|---|
| Satellite photogrammetry | Stereo satellite imagery | Decimetres to metres | Regional elevation models, large-area mapping |
| Manned aerial photogrammetry | Aircraft with large-format metric camera | Centimetres to decimetres | National mapping, city models, corridors |
| UAV (drone) photogrammetry | Multirotor or fixed-wing drone | About 1–3× GSD, often 2–5 cm | Topographic surveys, volumes, construction progress |
| Terrestrial / close-range | Handheld or tripod camera | Millimetres, sub-millimetre with coded targets | Buildings, heritage, accident scenes, industrial parts |
Close-range work is also called photogrammetry 3D scanning when it is used to digitise objects, though strictly no laser is involved.
What is aerial photogrammetry and how accurate is it?
Aerial photogrammetry is photogrammetry from images taken from the air, by aircraft or drones, usually looking straight down with additional oblique images for façades. A practical aerial photogrammetry definition is: mapping terrain and structures from overlapping air photos tied to ground control.
Drone photogrammetry accuracy on a well-controlled project is typically about 1 to 2 GSD horizontally and 1.5 to 3 GSD vertically. With a 2 cm GSD, that means roughly 2–4 cm horizontally and 3–6 cm vertically on hard, open surfaces. Accuracy is worse on vegetation, water and steep faces.
The biggest factor is control. Either survey 5 to 10 well-distributed GCPs for a small site, or use a drone with RTK or PPK camera positions plus a few GCPs and check points. Measure them with a survey-grade receiver such as our E1 GNSS RTK receiver, whose 60° IMU tilt makes it quick to occupy painted targets. Our guide to drone surveying with RTK and ground control points covers GCP layout, and choosing the aircraft is covered in survey drones and UAV mapping.
What is photogrammetry used for?
Photogrammetry is used wherever you need measurable 3D geometry and realistic colour from images: topographic mapping, volumes, construction monitoring, buildings, heritage and inspection. Photogrammetry surveying is now a routine part of many land survey and civil engineering firms.
- Photogrammetric mapping: orthophotos, contours and surface models for topographic and planning surveys.
- Earthworks and stockpiles: cut-and-fill and stockpile volumes from repeat flights.
- Construction: progress records, as-built checks and site logistics.
- Mining and quarries: pit faces, haul roads and bench mapping.
- Buildings and heritage: façades, roofs and textured 3D models.
- Infrastructure inspection: bridges, towers and dams, often combined with close-range imagery.
- Forensics: accident and crime scene documentation.
Photogrammetry vs lidar: which should you use?
Choose photogrammetry for open sites where colour, orthophotos and low cost matter; choose lidar where you need to measure under vegetation, in the dark, on featureless surfaces or with higher vertical reliability. Many survey teams use both.
| Criterion | Photogrammetry | Lidar / laser scanning |
|---|---|---|
| Measurement principle | Passive: triangulation from images | Active: laser range measurement |
| Vegetation | Maps the canopy top only | Multiple returns can reach the ground |
| Lighting | Needs good, even daylight | Works in darkness |
| Textureless or shiny surfaces | Poor matching, holes and noise | Generally measured, though very dark or reflective surfaces reduce returns |
| Colour and orthophotos | Native, high quality | Requires a camera added to the system |
| Equipment cost | Lower | Higher |
| Processing time | Longer (image matching) | Shorter for point clouds |
Indoors, photogrammetry needs careful lighting and many images; a laser scanner is usually faster and more reliable. For building interiors and plant rooms we recommend our terrestrial 3D laser scanner with built-in HDR camera, and for fast walk-through capture the handheld SLAM laser scanner. Our explainer on what lidar is covers the laser side in more depth.
What software for photogrammetry do you need?
You need photogrammetry software that performs bundle adjustment with ground control, dense matching and export of survey products; the right package depends on whether you process aerial or close-range data and how much control you need over accuracy. We do not recommend specific brands here, but these are the main categories of photogrammetry programs:
- Professional photogrammetry software (desktop): full control of camera calibration, GCP weighting, accuracy reports and coordinate systems. This is the standard for photogrammetric software used in surveying.
- Aerial photogrammetry software and UAV photogrammetry software: tuned for nadir and oblique drone flights, with flight-log import, orthomosaic and volume tools.
- Photogrammetry online (cloud) platforms: upload images and receive results; convenient for teams, but check data ownership, coordinate system support and accuracy reporting.
- Open-source photogrammetry program options: capable for research and learning, usually with fewer survey QA tools.
- Photogrammetry app for phones: fine for visualising small objects, but without control or calibration it is not a measurement tool.
Whatever you choose, check that it reports residuals on check points and exports to formats your CAD and GIS teams use. For point cloud cleaning and deliverables, see our point cloud processing guide.
Should you buy equipment or hire photogrammetry services?
Hire photogrammetry services for occasional or specialist projects; build in-house capability if you map regularly, because the main costs are training and software rather than hardware. Photogrammetry companies range from local drone operators to aerial photogrammetry specialists flying manned aircraft for national programmes.
When comparing UAV photogrammetry services, ask each provider for their GSD, overlap, control method, the coordinate system and geoid used, check-point accuracy report, and deliverable formats. Be wary of quotes that do not mention ground control or check points.
If you bring the work in-house, the survey kit that makes photogrammetry trustworthy is the same one you already use for control: a GNSS RTK receiver for GCPs and check points. To equip a crew with control equipment or add laser scanning for areas where photos struggle, request a quote and tell us about your typical sites.
Frequently asked questions
What is photogrammetric mapping?
Photogrammetric mapping is the production of maps, orthophotos, contours and elevation models from overlapping aerial or drone photographs. The images are adjusted to ground control so measurements are in a real coordinate system. It is widely used for topographic surveys, planning, mining and construction, and is often combined with lidar where vegetation hides the ground.
How accurate is drone photogrammetry?
With good overlap, sharp images and well-distributed ground control or RTK/PPK camera positions, drone photogrammetry typically achieves about 1 to 2 times the ground sample distance horizontally and 1.5 to 3 times vertically. For a 2 cm GSD that is roughly 2 to 6 cm. Always verify accuracy on independent check points rather than relying on software estimates.
Is photogrammetry the same as 3D scanning?
Not exactly. Both produce 3D point clouds and meshes, but 3D laser scanning measures distances actively with a laser, while photogrammetry calculates geometry from photographs. Photogrammetry 3D scanning is a common informal name for close-range image-based modelling. Laser scanning handles dark, shiny and featureless surfaces better; photogrammetry gives better colour at lower cost.
Do you need ground control points for photogrammetry?
For survey-grade results, yes, or at least check points. Without control, a drone model can be offset by metres and may be slightly warped. An RTK or PPK drone reduces the number of ground control points needed, but you should still measure several independent check points with a GNSS receiver to prove the accuracy of each project.
Can photogrammetry see through trees?
No. Photogrammetry only measures surfaces visible in the photographs, so in forests and dense scrub it models the canopy top rather than the ground. Small gaps may show some ground, but the result is unreliable for terrain models. Airborne lidar, which records multiple returns from each pulse, is the usual choice for mapping ground under vegetation.
What camera is best for photogrammetry?
For surveying, a camera with a large sensor, fixed focal length lens, mechanical or global shutter and good low-noise performance works best. Many mapping drones use one-inch or larger sensors of around 20 megapixels or more. Keep focus fixed, avoid zooming during a mission and use fast enough shutter speeds to prevent motion blur.
What is the difference between aerial and close-range photogrammetry?
Aerial photogrammetry uses images from aircraft or drones, usually looking down, to map terrain and sites over hectares or square kilometres. Close-range photogrammetry uses cameras within a few metres to a few hundred metres of the object, such as a building, part or accident scene, and can reach millimetre or sub-millimetre accuracy with targets.
Need equipment for this work?
Tell us the job, the country and the quantity. An engineer replies with a configuration and price within one business day. MOQ is one unit; OEM is available.
