Why is the photographic scale smaller than the measurement scale when surveying and mapping large-scale terrain?

The photographic scale can never be greater than the drawing scale. If so, you can only take an aircraft that is not higher than 50 meters from the ground. Nobody spends so much money.

Pay attention to the choice of spatial resolution in scale. For example, on the map of 1:2000, the ground resolution is 0.2m, which means that objects larger than 0.2m should be represented on the map. Therefore, the minimum requirement of remote sensing image is to select a photographic scale that is within 4 times of the maximum drawing magnification that can meet the plane accuracy, that is, greater than 1:8000. Why is 2000 four times? The reason is accuracy. Photos less than 4 times are enough, not mosaics. If the photographic scale is set too small, the image will be blurred, and even a "mosaic" pattern will appear, which will affect the drawing quality. On the other hand, if the photographic scale is too large, the information contained in the image cannot be reflected, which is "overqualified", resulting in unnecessary information loss and waste of resources. You don't need 1: 1 photography, that's not playing macro.

According to the provisions of "Selection of Aerial Photography Scale" in the Code of Urban Surveying and the Code of Aerial Photography, the following table can be obtained:

Ground Resolution of Surveying and Mapping Scale Aerial Photographic Scale Images (m)

1:500 1:2000- 1:3000 0.05

1: 1000 1:3500 - 1:4000 0. 1

1:2000 1:6000 - 1:8000 0.2

1:5000 1: 10000~ 1:20000 0.4~0.8

1: 10000 1:20000~ 1:40000 0.8~ 1.6

1:25000 1:25000~ 1:60000 1.0~2.4

1:50000 1:35000~ 1:80000 1.4~3.2