WHICH ACCURACY DO WE NEED IN GIS

K. Engsager

Danish National Space Center, Geidetic Dep., Copenhagen, Denmark

ke@spacecenter.dk

Map projections are discussed in relation to the accuracy that the users need and their expectation.

A short presentation of the transformation of an old map to a new datum is given. Some big errors appeared and the tracing of the errors is described.

The accuracy of the projection formulas is discussed in relation to the complexity of the formulas versus the difficulty of using and performing the calculations.