Geographic Information Systems: An Introduction, 3rd Edition

15.8 Functions for Engineering GIS

Geographical data are often used in solving such engineering problems as locating basic points, surveying properties, and planning various phases of roads, water supplies, sewerage, residential areas, and so on. These tasks have previously been accomplished using stand-alone PC programs, but the trend is to integrate them into urban GISs (Figure 15.25).

Surveying and other measurements

Surveying programs usually include functions for computing coordinate geometry based on in-field measurements, with interfaces to various surveying instruments. For engineering applications, they may be extended to compute the intersections between lines, between lines and circles, and so on. They must also support computations of various geometric figures so that exact geometry may be computed.

Other operations may also be performed. The layout data of plans may be computed, and various map projections may be manipulated and transformations made between projections. Often, the systems can produce standardized deed or other maps in local or standard formats. Some systems support the method of least squares, as well as automatic quality designations in the form of error ellipses. Other systems can combine GPS vectors with conventional measurements.

Manipulating terrain

To aid engineering work, digital terrain model systems have been developed to manipulate simultaneously as many as ten separate terrain layers, such as loose fill quantity, bedrock, and various geological ...