What Is Photogrammetry? Definition and How Surveyors Use It

Photogrammetry is measurement taken from photographs.

Photograph the same ground from several positions so the images overlap, then measure where the same points appear in each image, and the geometry can be solved into 3D coordinates, elevations and feature lines.

Those outputs are measured products, not just pictures.

Imagery that carries coordinates rather than only pixels is what makes the images usable as measured products — that is the sense this page uses throughout.

The word is also used well outside surveying, for measurement taken from photos of objects and scenes rather than terrain.

The underlying idea is the same, but the surveying practice covered here is built around mapping the earth's surface from the air.

Imagery covers an area in one mission rather than one point at a time — the property that suits the method to corridor and site mapping.

A flight captures what the camera can see from the air, and the measurement step turns that capture into data engineering and survey teams can build on.

The method has formal standing in the profession.

The NCEES Model Law's definition of the practice of surveying describes professional services using "such sciences as mathematics, … geodesy, and photogrammetry."

Per the same definition, that practice makes geometric measurements of the earth's physical or legal features and develops them into survey products such as graphics, data, maps and reports.

The Model Law is NCEES' template statute for state licensing boards, not any state's law — each board's own statute writes its practice definition.

But it shows why photogrammetry sits inside the survey-and-mapping world rather than beside it: the products the method makes are the kinds the Model Law's surveying definition already names — graphics, data, maps and reports.

At a survey or mapping firm, photogrammetry runs as a production pipeline: imagery is acquired, tied to ground control, oriented and measured, then compiled into deliverables.

The sections below walk through the measurement, the platform variants and the products.

The measurement rests on overlap.

A mapping mission photographs the same ground repeatedly from different camera positions, and a point that appears in two or more images can be positioned in three dimensions once the cameras' positions and pointing angles are solved.

The overlap is planned, not incidental.

ASPRS's flight-planning guidance puts endlap (forward overlap) at 55% to 85% depending on the project, with sidelap preferably 30% or more.

When structure from motion will be used, ASPRS recommends flying higher overlap: 75% to 85% endlap and 65% to 75% sidelap.

Tying the images together and to the ground is aerial triangulation.

ASPRS describes it as a simultaneous bundle block adjustment of control points and tie points, the corresponding points on overlapping images, and notes that airborne GNSS/IMU data captured during the flight can reduce how many ground control points a project needs.

Structure from motion (SfM) automates much of that matching.

ASPRS notes it is fully automated but can make matching errors, and that because it is usually run without ground control coordinates, the camera positions it derives lack scale and orientation.

The result sits in an image-space coordinate system that must be transformed into real-world coordinates — a step ASPRS says can require significant manual QA/QC.

With the images oriented, the measuring begins.

Two images of the same ground from different camera positions see each point from a different angle, and stereo instruments turn that difference into measured height.

O*NET's task list for the occupation describes compiling aerial photographs, survey notes and records for map preparation, and delineating control points, hydrography, topography and cultural features using precision stereoplotting apparatus.

Caltrans describes the compilation step as collecting observable points to create a 3D vector representation of photogrammetric measurements of the Earth's surface, done on stereoscopic mapping systems that generate coordinates and elevations and assign symbology.

Accuracy follows the chain.

ASPRS says the accuracy of aerial triangulation (or GNSS/IMU direct georeferencing) must be higher than the accuracy of the derived products — which is why flight planning, control and orientation are photogrammetry work, not setup for it.

The variants are named for where the camera sits: aerial from aircraft and drones, terrestrial from ground positions, close-range at short distances down to individual objects.

One caution before the detail.

The sourced standards and task lists this page draws on — ASPRS' positional accuracy standards, Caltrans' photogrammetry chapter, O*NET's task list — describe the aerial variant.

Our research for this page found no primary source in those files defining practice for the ground-based variants.

So the detail below sits on the aerial side.

Aerial photogrammetry is the variant behind the products listed further down, and ASPRS' accuracy standards treat it in two forms.

Traditional aerial photogrammetry is the aircraft-based capture whose products Caltrans' chapter and O*NET's task list describe; UAS (drone) photogrammetry is the other form its addenda cover, one ASPRS says may fly higher overlap than the traditional about-60%-forward-lap figure.

Both fly planned lines with heavy overlap and are oriented with aerial triangulation and ground control — ASPRS strongly recommends surveyed ground control points even when a drone has onboard RTK/PPK.

Terrestrial and close-range photogrammetry are the names for taking those images from camera positions on or near the site rather than from the air.

That is the naming-level distinction.

The sources this page draws on publish no practice detail for the ground-based variants, so this section makes no claim about their accuracy requirements, products or rules.

If you would be working that side, check current guidance from the bodies that write photogrammetric standards, such as ASPRS.

What the sourced, aerial side does show is a job market with named seats.

O*NET's occupation entry for cartographers and photogrammetrists (17-1021) lists sample reported titles including Aerial Photogrammetrist, Photogrammetric Technician, Stereo Compiler and Stereoplotter Operator, and its entry for surveying and mapping technicians (17-3031) lists Photogrammetric Technician and Stereoplotter Operator among technicians' reported titles.

BLS says cartographers and photogrammetrists spend much of their time in an office, though some jobs require fieldwork to collect data and verify results.

And the technology caveat applies to capture work of all kinds: BLS notes drones and other advancements make some aspects of survey work more efficient, while surveyors are still needed to review and interpret the output of those technologies.

Caltrans' photogrammetry chapter lists the typical products of the method: topographic mapping compiled as 3D vector representations of features and terrain, digital terrain models, photo rectification, and digital orthophotography produced from stereo photography plus terrain data.

Map compilation is the step that draws the vectors.

Caltrans defines it as collecting observable points to create a 3D vector representation of photogrammetric measurements of the Earth's surface.

Its most common product, per the same chapter, is 1"=50' scale 3D mapping — one state transportation agency's specification, and a look at what aerial mapping deliverables mean on DOT work.

Surface models split by what they capture.

ASPRS describes photogrammetric digital surface model (DSM) generation as creating a "first visible" product: features first visible from the air, such as trees and buildings, plus the ground in open areas.

USGS describes its DEMs as the bare-earth surface, excluding trees and buildings, and notes lidar point clouds record buildings, vegetation and the ground, from which DEMs are one of many products.

How the surface gets built varies too.

ASPRS says DSMs can be generated automatically by image matching such as structure from motion, or compiled manually in stereo — a route it describes as rarely used, highly accurate and very labor intensive.

Orthophotos are the image product: aerial imagery corrected so positions read as map positions rather than camera perspectives.

ASPRS describes orthorectification as photogrammetric processing that uses camera calibration information, a DEM, the source imagery and the exterior orientation parameters generated after aerial triangulation.

Even corrected imagery has limits.

ASPRS notes a conventional orthophoto is positionally correct for on-the-ground features only, so tall buildings lean over adjacent streets, while a "true" orthophoto has every pixel placed in its true geographical location, above-ground features included.

Where the products go is a jobs question as much as a technical one.

BLS describes cartographers and photogrammetrists as integrating land surveys and LiDAR using GIS, CAD and other software to build maps — in that picture, photogrammetry is one measured input to mapping work, not a rival to field surveying.

The core title is photogrammetrist — one of O*NET's sample reported titles for the occupation.

Federal statistics treat the role inside the combined occupation of cartographers and photogrammetrists (SOC 17-1021): BLS groups both into one occupation and gives no separate employment counts for photogrammetrists, so employment and outlook figures cover both titles together.

The work spans a pipeline with several seats: someone plans the missions and sets ground control, someone acquires the imagery, someone runs the triangulation and compilation, and someone QA-checks the surfaces and orthophotos before they leave the office.

Production runs on specialized photogrammetric software.

O*NET's technology skills file lists Intergraph ImageStation Stereo Softcopy Kit for cartographers and photogrammetrists, and BLS describes these workers as integrating land surveys and LiDAR using GIS and CAD — so GIS and CAD fluency is part of the seat, not an extra.

Where photogrammetric work becomes licensed surveying is a scope question decided state by state.

BLS says licensing for cartographers and photogrammetrists varies, may be state- or employer-specific and depends on duties.

Two sourced examples show the spread.

California's licensing board (BPELSG) has said drone flight planning, piloting and obtaining photography are not regulated by the Professional Land Surveyors' Act, but producing work depicting locations or elevations relative to the Earth's surface is.

And a federal appeals court affirmed in 2024 that North Carolina's board did not violate the First Amendment by requiring a surveying license to sell aerial maps and 3D models containing measurable data — a ruling the U.S. Supreme Court declined to review in 2026.

The Model Law itself contemplates the combination, giving boards a time-limited grandfather clause for licensing photogrammetrists with at least eight years' experience, two or more in responsible charge of photogrammetric mapping projects.

Measured mapping tied to real coordinates — especially anything touching boundaries, monuments or certified deliverables — is the work to check with the board before you accept it.

The outlook is measurable.

BLS Employment Projections project cartographer and photogrammetrist employment to grow 7% from 2025 to 2035, much faster than the average for all occupations.

The same BLS projections put openings at about 900 a year on average over the period.

If the work appeals, the photogrammetrist career guide covers the role side — duties, employers, credentials and the licensing question — and you can browse photogrammetrist jobs on SurveyorHires.

Career information, not legal or licensing advice — confirm scope-of-practice questions with your state licensing board.