Journal of Surveying Engineering

Mapping at large scales is presented as a process of forming a topographic and planimetric data base. The main stages of the process such as data collection, data editing, and data display are discussed. It is shown that all data processing, particularly the editing, can be performed without resorting to expensive special purpose equipment, e.g., interactive graphic stations, which makes the process suitable for smaller mapping organizations. Sample maps illustrate the procedures included in the software.

The trapezoidal rule and Simpson's 1/3 rule are the most common methods for computation of the area of irregular boundary. The trapezoidal rule assumes that the irregular boundary is composed of segments of straight lines while Simpson's 1/3 rule assumes parabolic curves. In this paper another approach based on describing the boundary as curves of a third‐degree polynomial is considered. This leads to Simpson's 3/8 rule for which a general formula is developed to give the total area when offsets at equal intervals dividing the area into a multiple of three sections are measured. Practical tests show that this method can give higher accuracy than the methods mentioned for the same amount of field work.

The analytical stereoplotter is a modern mapping tool, usually acquired by photogrammetric organizations with a history of providing clients with topographic maps. However, the analytical stereoplotter is much more than a mapping device. It is an extremely versatile and powerful system for extracting measurements from images. The exploitation of system measuring capabilities by a traditional mapping organization is hampered by biases and mind‐sets of personnel with only a mapping background. This presents barriers that must first be recognized and appreciated if they are to be overcome. Several of these barriers that have been identified while integrating a modern analytical plotter into a mapping group are discussed. The changing needs of the clients and the obstacles to meeting those needs are also described.

Results from an investigation have shown that errors resulting from the use of approximate methods for cross‐sectional area calculation are insignificant in earthwork volume determination. A simplified cross section can be substituted for the actual cross section in earthwork volume computation. Spacing between cross sections is the largest factor influencing accuracy of volume computation. Accuracy decreases with increasing distance between cross sections. The increase in density and quantity of the data base (i.e., the decrease in spacing between cross sections and the increase in point density along crosssectional profiles) can compensate for the decrease in cross‐sectional area calculation accuracy.

Standards of practice or recommended procedures in land surveying, often including statements concerning the accuracy or positional tolerance of surveyed points, are currently being established in many parts of the country. Computational techniques need to be adopted which allow land surveyors to determine whether surveys meet accepted standards. A pseudoinverse or inner‐constraint network solution provides estimates of the variance and covariance of point coordinates independently of any control established to adjust the network. The estimates of coordinate variance and covariance, derived from the inner constraint solution, can then be used to weight pseudo‐observations on the coordinates of legally controlling survey stations in a second solution to develop error ellipses and positional tolerances on newly established survey points and property corners relative to the legally controlling corners.