What is an orthomosaic photo?

In researching drones and aerial photography & mapping, you might find yourself bombarded by a lot of new jargon. One of the basic ones you should know is orthomosaic photo or orthophoto:

An orthophoto, orthophotograph or orthoimage is an aerial photograph geometrically corrected (“orthorectified”) such that the scale is uniform: the photo has the same lack of distortion as a map. Unlike an uncorrected aerial photograph, an orthophotograph can be used to measure true distances, because it is an accurate representation of the Earth’s surface, having been adjusted for topographic relief,[1] lens distortion, and camera tilt.

[Via Dronemapper]

Quick decent 2 minute comparison of topographic and orthophoto maps:

Another wonderful Dennis Baldwin video on an alternative program to Dronemapper called Open Drone Map:

But basically, an orthomosaic is a series of individual photos which are programmatically matched up so that they form a new composite image, consisting of all the smaller ones. Like this:


And via Steven Mather, the creator of Open Drone Map:

OpenDroneMap: Open Source Toolkit for processing Civilian Drone Imagery

“OpenDroneMap is an Open Source Toolkit for processing Civilian Drone Imagery. As small unmanned aerial systems have dropped in price and become readily affordable, software for making meaningful geographic data from civilian drones has not. Until now.
“OpenDroneMap is fully Free and Open Source postprocessing tool for highly overlapping unreferenced imagery, turning unstructured data (simple photos) into structured geographic data such as colorized point clouds, digital surface models, textured digital surface models, and highly detailed orthophotography.
The project can be found at http://opendronemap.github.io/odm/.”