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The returned number of available bytes is a hint , but not a guarantee , that it is possible to use most or any of these bytes . The quality of the data depends on the swath width , defined by the unobstructed angle through which the scanning mirror is designed to rotate , and is limited by changes in the atmospheric path lengths and in the size of the pixel for off-nadir angles and by the available electrical bandwidths for tape recording or telemetry of the image data . The number of unallocated bytes is most likely to be accurate immediately after this call . Updates will be made as new information and / or drivers becomes available . The returned number of unallocated bytes is a hint , but not a guarantee , that it is possible to use most or any of these bytes . Processing ( granting or rejecting ) floor control requests is done by the one or more floor chairs or by the server itself , depending on the policy . A reasonably correct estimate of dimensions is essential to correct identification .