When you upload your overlapping drone mapping images, we use a number of different structure from motion algorithms to bring them together into a single orthomosaic. Many datasets are processed within an hour and will be available to view on GeoNadir when they are ready. Large or complex datasets can take longer, but if you're the person who uploaded the data you can head off for a cup of coffee while we take care of the rest. We will send you an email when it's ready.
When the orthomosaic is complete, this will also allow us to populate the statistics based on the area covered and GSD or ground sample distance. Often that's referred to as the pixel size of the image.
Note that the GSD and area sizes calculated in our platform are estimates. Factors such as the sensor size, image resolution from metadata, and different coordinate systems selected can vary the outputs slightly.