What is the difference between comparing the projection properties of aerial photos and topographic maps?

Hello, to put it bluntly: topographic map is a special aerial photography, and aerial photography is a foundation of topographic map.

Topographic map refers to the projection map of the undulating form of the surface and the position and shape of ground objects on the horizontal plane. Specifically, the ground features and landforms on the ground are horizontally projected (along the vertical line to the horizontal plane) and drawn on the map according to a certain proportion, which is called topographic map.

Aerial photography can be divided into vertical photography and oblique photography according to the tilt angle of the photo (the tilt angle of the photo is the angle formed by the main optical axis of the aerial camera and the ground vertical line (main vertical line) passing through the center of the lens).

When the inclination angle is equal to 0, that is, the main optical axis is perpendicular to the ground (coincides with the main vertical line) and the photosensitive film is parallel to the ground, it is vertical photography. However, due to various reasons in flight, the tilt angle cannot be absolutely equal to 0, and generally it is called vertical photography when the tilt angle is less than 3. A photograph obtained by vertical photography is called a horizontal photograph. In general, the shape of the ground object image in horizontal photos is basically similar to that of the top of the ground object, and the proportion of each part of the photo is also roughly the same. Transverse photos can be used to judge the positional relationship and measure the distance of each target.

If the inclination angle is greater than 3, it is called oblique photography, and the obtained photos are called oblique photos. This kind of photo can be used alone or in combination with the horizontal photo.

I hope I can help you.