The ephemeris data, giving the position of the satellite every minute, are encoded with a 0.1 m resolution. Is it indicative of the actual accuracy of the knowledge of the satellite position?
On Spot 1, 2 and 3, the encoding of the ephemeris data posted in the Ancillary files of the SPOT Scene products does not reflect the actual accuracy of these data which is a few hundred metres (rms). However, with Spot 4, the use of data coming from the DORIS passenger allows to get an accuracy better than 1 m. Just note that this applies only to the position of the satellite on its orbit; one has to realise that the final location accuracy of the images on the ground depends also on the pointing accuracy of the spacecraft and its instruments (attitude of the spacecraft, mirror pointing angle, etc). This lead to a final location accuracy between 300 and 500 metres (rms).
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