This paper describes the integration of a ground surface modelling system with a General Draughting System. The integration results in the combination of the modelling and analysis operations with the production of final site survey and setting out drawings. It shows how the user, based at a standard C.A.D. workstation, can define surface models by interactively selecting information from a drawing held within the system database. The information is of the form of random spotheights across the surface area defining surface levels, and graphic blocks defining pathlines and boundaries. This technique of data acquisition is more accurate than the methods of string digital terrain model or square grid matrix as no preconditions are set as to the position of the data.

The paper describes how, having defined the models he wishes to work with, the user can then manipulate and restructure the models to provide the optimum solution to the particular surface modelling problem he is attempting to solve. Various graphical and numeric output options are available to the user to evaluate the effects of his modelling actions.

The paper demonstrates an important application of C.A.D. modelling and draughting techniques to the civil and architectural engineering industries.

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