Image coordinate

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In astronomy and photogrammetry, image coordinates are the 2D coordinates of objects on photographic films or plates .

The image coordinates are usually referred to as x, y . They are measured on the comparator , a plate measuring device with a movable slide for the photo carrier, as well as with measuring microscopes and micrometers. At well-defined points (ideal control points , connecting stars that are not too bright , etc.), the measurement can be carried out with an accuracy of up to 0.001 mm (1 µm).

The image coordinates are converted into the desired coordinate system using a suitable coordinate transformation. With this transformation, even small systematic errors in the mathematical model can be taken into account or eliminated.

In the case of CCD sensors , the image coordinates result directly from the grid of the pixels , i.e. H. the electronically read out rows and columns of the chip. If an image point exposes not just one pixel, but several, the image coordinates can be determined very precisely - to fractions of a pixel.

In a figurative sense, one can also speak of image coordinates in electronic imaging processes , in particular in the case of scanning methods such as computed tomography or in the case of a scanning tunneling microscope .