Terrel L. Shields
Elite Member
- Joined
- May 2, 2002
- Professional Status
- Certified General Appraiser
- State
- Arkansas
Aerial photography has to be corrected. This is done automatically to some extent with modern photogrammetric tools within the computed image. (It is correct that google earth photography is digital thus is "imagery" and not "photography" technically speaking.)
Since the plane flies along a path only the line directly below is not distorted, provided the plane is flying level or the camera compensations accordingly. Therefore, any measurement of a building is subject to being slightly "off" but again, we are talking 5% difference max usually.
3-D is simply having 2 camera shots overlapping, which is done in conventional aerial imagery by overlapping flight lines about 60% assuring at least 2 parallel lines have the same image thus can create the 3D effect.
However, you can see that impact of distortion if "flying" low in Google Earth up in the mountains where the mountains appear to be tilting towards you. If the light is just right, it inverts, leaving you the sensation of of creeks on ridge tops and snow covered valleys.
Since the plane flies along a path only the line directly below is not distorted, provided the plane is flying level or the camera compensations accordingly. Therefore, any measurement of a building is subject to being slightly "off" but again, we are talking 5% difference max usually.
3-D is simply having 2 camera shots overlapping, which is done in conventional aerial imagery by overlapping flight lines about 60% assuring at least 2 parallel lines have the same image thus can create the 3D effect.
However, you can see that impact of distortion if "flying" low in Google Earth up in the mountains where the mountains appear to be tilting towards you. If the light is just right, it inverts, leaving you the sensation of of creeks on ridge tops and snow covered valleys.