ABSTRACT
In topographic surveys, point information data are gathered in the form of coordinates (with height information) and point feature descriptions. The main factors that determines the level of detail (i.e., amount of information to be gathered for an area) are the required map scale and intended use. The second element in the design of a topographic survey is the project control. A project control will provide a framework for the point coordinates. For example, on the basis of a control survey, line bearings and distances between project points can be computed and represented on a map. This chapter will look at important considerations in the following areas:
• The scope and requirements of a topographic survey
• Finding sources of existing survey data and geospatial information
• Establishing control at a project site
• Selecting map scales, feature location tolerances, and contour intervals
7.1.1 Project Scope and Requirements
Topographic survey requests are often general in nature and often accompanied with a request for a cost estimate to perform the survey. In many cases, the survey details, site conditions, scope, and accuracy requirements are not specified; or, more often than not, the actual work required far exceeds the given budgeted amount. The burden is often placed on the surveyor to design a survey accuracy and density that will best satisfy the design requirements that the requesting entity desires. It is rare that the requesting user ever obtains the detail required for the project. Likewise, it is equally rare that the surveyor is able to perform the quality of survey he feels is necessary to adequately define the project conditions. In many cases, an advance site visit may be necessary to assess the actual conditions and provide a reliable budget estimate (time and cost) to the requesting client (Figure 7.1).
