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3.4 Units of measure

The unit of angular measure is the gon. For linear measures, no definite dimension is assumed; some constants, however, have to be defined anew (if necessary).

It is necessary to differentiate between units in the object space and those in the image space. All lengths in the object space must have a uniform unit. These are: Coordinates, coordinate differences, distances, the eccentricity vector e', earth radius, and all corresponding standard deviations. The units in the image space must also be uniform. These are: Image coordinates, camera constants, principal-point position, and the corresponding standard deviations.

Generally the following units should be applied:

  • in the object space metre : [m]
  • in the image space millimetre : [mm]
  • for angles : [gon]

If metres are not used in the object space, then the earth radius must be redefined in order to correct measured zenith distances (see CONS statement Section 5.5).

If millimetres are not used in the image space, then a format adaptation factor is computed for each camera by choosing the largest value of image coordinates. The same applies for images with another than the aerial-photo format of 230 mm x 230 mm. The above mentioned factor is necessary for computation of the additional parameters. It internally transforms the image coordinates for computation of additional parameters to the required format of 230 mm. For new digital aerial cameras with several sensor heads the image format in BINGO is partly pre-programmed already or it can be defined by an individual camera data file.