HJW GeoSpatial, Inc.- Services- Aerial Triangulation

HJW GeoSpatial Services

Aerial Triangulation
Aerial triangulation is a mathematical process used to determine the position and orientation of each photograph at the moment of exposure. Aerial triangulation solves for each photo’s exterior orientation parameters, which convey the information necessary to convert image measurements into ground coordinates, as well as determine image points that correspond to points on the ground. Knowledge of the orientation parameters enables photogrammetric principles to be applied to planimetric and topographic map compilation, orthophoto production, digital terrain model editing and creation, and other important support tasks.

In general, the quality of the exterior orientation parameters and the scale of the photography are the determining factors in the quality of the mapping products. In the case of orthophotos, the terrain model also plays a key role. Therefore, aerial triangulation is a critical step related to the project’s quality, and is at the heart of all photogrammetric processes.

Our aerial triangulation software supports both softcopy and analytical aerial triangulation, and incorporates airborne GPS/IMU data to constrain and guide the process. Our in-house experts have written proprietary software to aid in the aerial triangulation process. One program, which we use as part of our standard workflow, performs image point corrections for radial and decentering lens distortions. This practice is not an industry standard, as most off-the-shelf aerial triangulation software packages only correct for radial lens distortions.

Photo scale, camera/film characteristics, flight line configuration, ground control layout, GPS/IMU availability, and sometimes the terrain play a role in the accuracy of aerial triangulation. HJW’s policy requires at least two aerial triangulation specialists to validate results before considering the task complete. Redundant control information, statistical analysis, and subsequent quality checks all enable us to provide reliable results.