What it is and the problem it solves
Photogrammetry is a method for extracting reliable 3D spatial measurements from 2D images. It solves the problem of quantifying physical objects and environments without direct contact.
How it works
It identifies matching points across two or more images. It constructs rays from known camera positions to those points. It calculates 3D point locations where the rays intersect — triangulation. It refines those coordinates by minimising measurement errors across all points and images — bundle adjustment.
What works
Stereophotogrammetry works: it estimates 3D coordinates from two or more images taken from different positions. Single-image photogrammetry works when image scale is known and the target lies on a plane parallel to the image plane. Bundle adjustment works: it refines point coordinates using the Levenberg–Marquardt algorithm to minimise reprojection error.
What does not
It does not recover absolute scale from a single uncalibrated image. It does not infer material properties, lighting, or occluded geometry. It does not work reliably when common points cannot be identified — such as on textureless, reflective, or moving surfaces.
What it changes
It replaces physical surveying with image-based measurement. It enables reconstruction of inaccessible or hazardous objects — like heritage facades or volcanic terrain — using only photographs. It shifts spatial documentation from contact-based to optical methods.
Is it worth your time
Yes, if you need metrically accurate 3D models from images and can control image geometry, scale, and overlap. No, if you require real-time output, operate without ground control, or expect accuracy without calibration.
