3D Robotics Aero-M - Manual (Page 43)

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Aerial Imaging Concepts
Understanding key concepts in aerial images can help you understand the mission planning process and create better maps.
Distance-Based Imaging
By default, the Aero captures only the images required to create the map. The autopilot monitors the distance traveled by the Aero and
sends a command to the camera to capture an image at the distance interval specified by the camera trigger distance parameter (CAM_
TRIGG_DIST). This parameter is set by the Mission Planner Survey Tool during survey configuration by calculating the minimum distance
between images based on the parameters specified for the survey (altitude, overlap, sidelap). This distance-based imaging allows for more
precise data collection, resulting in less images and data storage cost.
Once configured, the Survey Tool creates an event at the start of the mission script (after takeoff) to set the camera trigger distance to the
specified interval and an event at the end of the mission (before landing) to reset the camera trigger distance to 0. Therefore, while on the
ground and during landing, the camera captures no images because the camera trigger distance is set to 0 m.
Time-Based Imaging
The Aero is also equipped to capture images at a consistent time interval instead of using distance. This function can be useful if you want
to capture images over an area without planning a mission. This time-based imaging results in more images per area, and therefore more
processing time and storage cost. See the intervalometer option on page 43 to enable time-based imaging.
Overlap and Sidelap
To capture images for the map, the Aero flies a lawnmower-like pattern in strips across the survey site. The front-to-back overlap between
sequential images is called overlap; the side overlaps of adjacent pictures in different strips is called sidelap. The overlap and sidelap
parameters in the Survey Tool (see Advanced Options page 16) determine the distance between images and the number of images to be
captured based on the projected ground area that each image will cover, called a footprint. The Survey Tool uses a default overlap of 50%
and a default sidelap of 60%. Increasing overlap and sidelap improves the accuracy of the map while increasing flight time and processing
time.
In the Survey Tool, Distance between Images shows
the specified camera trigger distance that will
be assigned to the mission. You can also see
the projected image footprint size and the total
number of images to be captured.
Default overlap: 50%
Default sidelap: 60%