Camera Features

A metric camera can be defined as an accurate central projection (perspective), strictly geometrical, where projection center is located at a c distance from pictures's principal point.

Main parameters of that geometric-matematical simplified model, called internal orientation elements, are the main distance (c) and principal point's image coordinates (x₀,y₀).

That ideal model doesn't match perfectly with reality: lens distortions and other camera particular features change picture properties and they must be identified if taken pictures are used in photogrammetry applications.

Parameters that describe internal camera features are traced with Calibration Process.

Calibration Process

With the Calibration Process the camera internal orientation parameters are well-known, so the camera become a "metric camera" and can be used for measurement purposes.

Since camera internal parameters can change, calibration process must be repeated after a time. Camera's phisical features are determined by travel hits, temperature and pressure changes, so check its Calibration again is needed.

Calibration Process, executed into Menci Software's Calibration Labs, consists in taking photos to particular panels and polygons. Then that photos will be processed with special calibration softwares, produced by Menci Software.

Some parameters are obtained from that process and they are stored in a calibration file (Camera Passport).

Time needed to complete a calibration process and do quality tests is usually a week, from when camera (with charger and other kit) is received.

Camera Passport

The Camera Passport file produced by Menci Software provides about following informations:

• Fiducial Marks
• PPA and PPS coordinates
• Main Focal Length (c) expressed in mm and pixel unit
• Radial and tangential distortions parameters
• Calibration date
• Principal Point coordinates (in pixel)
• Image dimensions (in pixel)
• Pixel Size
• Some other informations like camera and lens serials

These parameters are used to define an Internal Orientation for every picture taken by a calibrated camera.

For further information please contact Francesca Ceccaroni