Types of Image Distortions
Image distortions happen when images are not well matched or stitched during the photogrammetry process. This usually happens due to a lack of clear distinguishable common features in each image.
One of the most common errors we see happens during stitching due to wrong overlap settings. For images to be stitched together successfully, there need to be lots of common points within them to ensure that your photogrammetry software can place them correctly. This often results in distortions at the edge of sites, as well as around tall objects. Setting correct image overlap settings is particularly important when you have tall objects in your site, as the taller an object is, the less likely it is that you will have an image with a similar viewpoint of said object.
Another cause for distortions in images is errors in stitching images of homogenous sites, such as dense forests, large bodies of water, etc. In these cases, there are usually not enough distinguishable features between the images to match them correctly during the stitching process. A third common reason for image distortion is poor image quality, which can arise for a variety of reasons. If the wrong settings are selected during the data collection process, images collected during your flight could end up distorted. Images that are grainy, blurry, or too dark will not stitch correctly and cause issues.
How are artifacts treated in the data processing stage?
If your images happen to have a large number of artifacts, we, unfortunately, will not be able to safely distinguish between artifacts and true site features. To deliver accurate and valid results, the site should be surveyed again with the correct image collection settings ensured.
Currently, the only artifact that the AirWorks software can identify is terrain which is obstructed by foliage. In these cases, AirWorks communicates with you to inform you that while we can proceed to process a site that is obstructed with foliage, the 3D contours may not be robust.
Avoiding Image Distortions
There is no one-size-fits-all approach to avoiding image distortions, but it ultimately comes down to proper image collection and choosing the right settings. These will all vary depending on the type of site, time of day, type of camera, etc. You should consult with your drone pilot or service provider before flying a site to communicate the necessary setting and parameter requirements for successful image-stitching and photogrammetry, as well as for autonomous drafting with AirWorks.