Here is a simplified Excel spreadsheet that can be used to assist UAS aerial photo mission planning for those that don’t have access to mission planning software either provided with the UAS or custom written. The spreadsheet uses the following inputs (cells are highlighted in yellow) provided by you for your mission:
- Camera and lens parameters including the CCD focal plane size in pixels and millimeters and the actual lens’ focal length. This is the true focal length, not 35 mm equivalent, and should be the value written into the photo’s EXIF metadata during imagery collection. A great source of camera and lens information can be found here: www.dpreview.com. Go to the camera tab at the top of the page and then select camera manufacturer and search for your model. You’ll find focal plane info in the specifications tab.
- Mission and imagery collection parameters including UAS ground speed, flight elevation above ground, imagery overlap, both forward and side, and the area of interest (AOI) width and length. The AOI assumes a rectangle with the shorter side the width and longer side the length.
After you have input the various parameters for your mission the spreadsheet provides the following outputs (these cells have no color fill and should be locked to the user):
- Focal plane pixel size,
- Camera shutter speed to minimize image blur,
- Imagery ground sample distance or size of the pixel on the ground,
- Photo or frame size on the ground, width and length,
- Flight line spacing to achieve side lap input and the number of flight lines for the AOI,
- Distance between successive photos in the flight line to achieve forward overlap input and the number of images for each flight line,
- And, the total number of images for the AOI to achieve the coverage desired.
- Platform ground speed input should consider the fastest speed the UAS could achieve during the mission in case of a tailwind, for example,
- Dronemapper recommends no less than 60% forward overlap and no less than 40% side lap. For difficult homogenous scenes and significant terrain elevation changes one should increase overlaps to 75% forward and 60-75% side.
- Always extend the width and length of the AOI to insure full coverage of the complete scene of interest. This minimizes digital elevation model (DEM) noise at the AOI boundaries.
- Discussion of the image collection geometry and formulas used can be found here: https://dronemapper.com/uas_photogrammetry_processing.