The relation between the scale of captured aerial photos and scale of the extracted features,

[JamalNUMAN]

The relation between the scale of captured aerial photos and scale of the extracted features,

The overlaps (60% front and 20% side) between the captured aerial photos ensures having 3D model and thus orthophoto can be built and features and contours can be extracted.

The issue here is that if the aerial photos are captured with a scale of 1/9,000 then which mapping scale and contour intervals can be derived from this scale (1/9,000)?

The scale of aerial photos can be easily calculated if the focal length (f) of the camera and flight height (h) above the ground are provided from the formula below:

Scale = f/h

For example, if the focal length is 305mm and the flight height is 2700 m, then the scale=(305/1000)/2700 = 1/9,000

1. Then which mapping scale can be set for the extracted features from the aerial photos of 1/9,000 scale?
2. Which contour interval can be extracted from this scale?

Is there mathematical equations that support such calculations?

Best

Jamal

[KevinCrichlow1]

Following on from your example above: - 

A camera with a 28mm focal length lens flown at a height of 1800m AGL will form an image on the detector array at a scale of 0.028:1800 or 1:65,000

Thus it will have a scale factor of the inverse which is 65,000

The GSD (Ground Sample Distance) of an image can be calculated as 

Collection GSD = (detector element size) X Scale Factor

If each detector element in the array is 0.0009mm (9 x 10^-6m) then the collection GSD in your case would be (9 x 10^-6m x 65000) or about 0.6m 

Source: Aronoff S, Remote Sensing for GIS Managers, pg 78.

[abdullahqasrawi]

Dear Kevin Crichlow

The relationship between photo scale and GSD is clear.
the problem here is that i want to find  mapping scale (scale for extracted features) from aerial photos captured at specific scale with specific GSD

if i have two groups of aerial photos

first group with GSD = 15 cm and captured at scale 1/20000
and the other group with GSD = 40 cm and captured at scale 1/ 50000

actually the first group cover small area with huge details but the other group cover large area with less details so logically  i need different scales.

how can i find the mapping scale  for each group?

[KevinCrichlow1]

ASPRS POSITIONAL ACCURACY STANDARDS FOR DIGITAL GEOSPATIAL DATA

See pg A14 - A15 (Both tables)