ADS 40 – 51&52 Sensor Head

ads40-1 Different imaging concepts:

Image overlap is required if 3D measurements are to be made or DEMs (Digital Elevation Models) and orthophotos are to be produced. Only images taken from differing vantage points (different positions in space) allow for stereo viewing or automated image matching.

While analog aerial cameras make photographs at certain intervals to satisfy the need for views from differing positions, the airborne digital sensor is continuously recording CCD line data from three CCD lines which themselves are pointing in different directions.

Images recorded simultaneously:

For easy understanding of the three-line principle it is best to discuss the differences between this principle and the well-known principle of vertical photography based on a central perspective.

 

An analog camera photograph is the equivalent of about 25,400 by 25,400 pixels if you scan the image at a resolution of 9 microns.

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Definitions for the pushbroom image:

n  individual lines are either  forward view lines, nadir view lines or backward view lines.

n  putting lines of the same viewing angle together form a square or a rectangle called a scene, the sides of which are approximately the length of a CCD line.

n  putting lines of the same viewing angle together to form a rectangle of undefined size or length is called a strip

Panchromatic and spectral band filters:

The ADS40 captures strips of imagery with linear CCD arrays, as opposed to discrete aerial images with a square or rectangular CCD sensor.

Panchromatic imagery is captured looking forward, nadir and backward from the aircraft. Near infrared information is also captured close to nadir, whereas the red, green and blue color bands are forward looking

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