Photogrammetry and structured light 3D scanning both capture geometry from physical objects — but they work differently, produce different levels of accuracy, and suit different project types. Choosing between them (or knowing when to use both) isn’t about which technology is “better.” It’s about matching the tool to what the project actually requires.
Here’s a clear breakdown of how each works, where each performs best, and how to decide which is right for your project.
How Photogrammetry Works
Photogrammetry reconstructs 3D geometry from a series of overlapping photographs. Software analyzes the images, identifies matching features across photos taken from different angles, and uses the geometry of those matches to calculate the three-dimensional position of each feature. The result is a point cloud or mesh that represents the photographed object or environment.
The key advantages of photogrammetry are accessibility and scale. It requires only cameras — which can be anything from a professional DSLR to a drone-mounted sensor — and processing software. It can capture objects of any size, from small artifacts to entire building exteriors or large outdoor sites. For many applications, it produces geometry that’s more than adequate.
The limitations are accuracy and surface texture dependency. Photogrammetry relies on visual features in the images to establish geometry — surfaces that are featureless, reflective, or translucent are difficult or impossible to capture reliably. Accuracy is typically in the range of millimeters to centimeters depending on camera quality, image overlap, ground control, and processing quality. For engineering-grade applications that require sub-millimeter accuracy, photogrammetry often falls short.
How Structured Light 3D Scanning Works
Structured light scanning projects a known pattern — typically a grid or series of stripes — onto the object’s surface and captures how that pattern deforms. By analyzing the deformation, the scanner calculates precise surface geometry. This is a direct measurement of physical surfaces, not a reconstruction from photographs.
The advantages are accuracy and reliability. Structured light scanners routinely achieve accuracy in the range of tens of microns — well into the territory required for engineering, tooling, and quality inspection work. Surface capture is reliable for most materials and geometries, though highly reflective and transparent surfaces still require preparation or specialized approaches (covered in detail in our post on scanning reflective and transparent objects).
The limitations are scale and setup. Most structured light systems have a working volume measured in centimeters to about a meter — large objects require multiple scans that must be registered (aligned) into a single unified model. Setup time is higher than photogrammetry, and the equipment is more specialized. Our 3D scanning services use structured light scanning as our primary tool for engineering-grade work.
When to Use Photogrammetry
Photogrammetry is the right choice when:
- Scale is large. Buildings, vehicles, landscapes, large structures — anything where structured light scanning would require an impractical number of passes to cover.
- Accuracy requirements are modest. Visualization, digital archiving, general documentation, VR/AR asset creation — applications where millimeter-range accuracy is acceptable.
- Accessibility is limited. Remote locations, outdoor environments, or situations where dragging specialized scanning hardware is impractical. A camera and processing software can go anywhere.
- Speed matters more than precision. Photogrammetry capture can be faster for large scenes, especially with drones or multi-camera rigs.
When to Use High-Resolution Structured Light Scanning
Structured light scanning is the right choice when:
- Engineering accuracy is required. Reverse engineering, quality inspection, tooling verification, and any application where dimensional accuracy in the sub-millimeter range matters.
- The deliverable is a CAD model. Structured light scan data has the geometric accuracy needed to produce a reliable parametric CAD model through reverse engineering. Photogrammetry data typically doesn’t. Our reverse engineering services are built around structured light scan data for this reason.
- Surface detail at small scale matters. Fine features — thread profiles, tight radii, subtle surface texture — are better captured by structured light than photogrammetry.
- The object is small to medium sized. Structured light scanning excels in the range of a few centimeters to about a meter — the typical size range for engineering parts, components, and artifacts.
When to Use Both
Some projects benefit from combining methods. A large industrial facility might be captured with laser scanning or photogrammetry for spatial context, with structured light scanning used on specific critical components where engineering accuracy is needed. A heritage documentation project might use photogrammetry for the building exterior and structured light for detailed ornamental elements where surface geometry needs to be captured at high resolution for fabrication reference.
The decision framework is the same in both cases: what accuracy does each part of the project require, and what’s the most efficient way to deliver it?
If you’re scoping a project and aren’t sure which approach is right, get in touch with our team. We work with both technologies and can help you figure out the most appropriate method — and the most cost-effective path to the geometry you actually need.
