An assessment of aerial surveyed string digital ground models

The Thesis reports research carried out in the Surveyor's Department of Durham County Council, into the use of ground models in highway design. The research isolates the various sources of error that contribute to the ultimate error in earthworks quantities, obtained from an aerial surveyed string digital ground model, and assesses their relative importance. The research covers the following topics : 1. Isolation of the various sources of error contributing to error in calculated quantities e.g.(a) error in preparation of model.(b) error inherent in the type of model specified.(c) error in technique used to interpolate from the model. 2. Detailed investigation of each source of error to compare magnitude and type (i.e. random or systematic). 3. Specification of a procedure for testing a model to assess its accuracy both for design quantities and ultimately for contractors acceptance. The use of the aerial surveyed string ground model is justified as being an invaluable aid to the practising highway engineer and a practical method of proving the accuracy of a model is provided. To support the research two test areas have been precisely levelled and the results are discussed, together with modifications to data collection and data retrieval techniques.