A support arrangement for a registration device such as a surveying instrument

The invention relates to a support arrangement (3) for a registration device (4), forming a first surface (7) having a known position in relation to a ground (14), and a second surface (8) adapted to support a registration device (4), said first and second surfaces (7, 8) having an asserted fixed relationship, wherein said support arrangement (3) in use is subjected to external time dependent influence resulting in an undesired displacement of said second surface (8) in relation to said first surface (7). Said support arrangement (3) is provided with means (16) for measuring a parameter from which said displacement at least partially may be obtained, and means (17) for obtaining said displacement or a value analogous with said displacement from said parameter. Further, the invention relates to a support arrangement (3) comprising a registration device (4), such as a total station (4), and a levelling means being adapted to compensate a value registered by said registration device (4) for said displacement.