When using aeronautical data, it is necessary to distinguish between individual methods of data processing. This has a major impact on their accuracy. The most common output is orthophoto… or not?
Measurement and vectorization
During measurements and vectorization from aerial images, serious errors can occur due to image distortion, see figures.
In the true orthophoto, the heel of object A and its top A ‘ are in the same position.
In the false orthophoto (or aerial image), there was a significant difference in the position of the image between the heel (A) and the top of the object (A ‘).
Conclusion on vectorization:
• From the right orthophoto it is possible to vectorize in all levels
• Objects can be vectorized from false orthophoto only at ground level
• It is not advisable to vectorize from an aerial image at all
When will you meet?
For high-resolution images, a true orthophoto (typically drone data) is usually used. For medium and lower resolution images, a false orthophoto (aircraft, satellites) is used. This is due to the requirements for accuracy and then also the size of the perspective distortion.
Close-ups will be very distorted and need to be corrected. Otherwise, they are almost impossible to combine into a false orthophoto.
Images from a greater distance / height have less perspective distortion and are therefore less distracting and "just" correct the tilt errors of the image.
Author: Ing. Ondřej Kočí