AERIAL PHOTOGRAPHS.
Vertical Aerial photograph or Air Vertical
Is a photograph taken from an air craft with the camera pointing vertically over the area being photographed.
Characteristics of Vertical Aerial Photographs
- They show a rectangular shape of the tops of buildings.
- They show only the tops of objects in the centre of the photograph but on the margin i.e. more sides may be seen.
- The size and height of these photographs are greatly reduced and difficult to tell.
- The horizon is not shown in vertical aerial photographs.
- The shadows of vertical aerial photographs appear blurred.
- They cover wider areas as they are taken by cameras in moving aircraft from the time it flys until it lands.
- Aerial photographs cover very large flat and almost featureless areas.
- When a stereo viewer instrument is used the objects can be seen in three dimensions.
- Areas of vertical aerial photographs without prominent relief features appear dull and flat when seen using naked eyes. Where relief features occur, the shadows are sharp and clear e.g. troughs, tors e.t.c.
- The scale of vertical aerial photographs is not the same because of the differing heights of the objects and land features.
- The maps produced from vertical aerial photographs have small scales as they show a wider area.
- Vertical aerial photographs are very difficult to read and interpret.
Oblique Aerial Photographs
These are taken when the camera in the aircraft or aeroplane is tilted at an angle from the earth's surface. They are taken from low flying aircraft or tops of hills. Air obliques are taken from the windows of a flying Aeroplane at an oblique angle.
Characteristics of Oblique Aerial Photographs
- The size and height of objects are reduced greatly.
- They cover large areas and show panoramic views of the countryside.
- The sky line or horizon is shown on the photograph since they are taken from a low flying aircraft or the top of a hill.
- The objects can be seen on three dimensions i.e. The top and the other two sides.
- The objects appear to be below you when looked at them and the tops of the features are seen.
Sometimes the horizon may not be seen in air obliques which were taken from a low flying aircraft and these are called low-obliques. Air obliques which were taken from a high flying aeroplane show the horizon.