Low overlap for orthomosaics only, but how low?

PIX4Dcapture
1

What are the primary reasons of recommending no lower than 60% side overlap?

The reason I ask is multifold. Traditional photogrammetry and mapping has only needed 30-40% side overlap and 60% front overlap. At 40% side overlap, our collection will increase in speed and capacity by over 200%, and that saves a lot of time! As long as front overlap is 60%, there are always at least 2 photos of every location, and that is all that is necessary for an orthomosaic. The point cloud is rarely a selling point for our clients, so a little more noise won’t make a difference on our projects. 

In addition, we have the following features that will keep our accuracy in check:

  • PPK GNSS receiver for positioning +/- 2cm
  • IMU data for Roll/Pitch/Yaw
  • Pre-Calibrated Lens so no optimization needed
2

Hi Nathan,

It really depends on the area you are imaging. For example, if there are buildings, the overlap if for the ground might be 60%, but on the top of the roofs, there might be very little overlap. Also, if the area is very homogenous, we recommend more overlap. 

For image calibration, the key points are matched with other image key points after they are extracted from each image (step 1). So if all your images are being calibrated after step 1 and you get a good result (with no holes, or stripes), you are good to go.

You would need to perform overlap tests for your area and check what minimum overlap can be used.