When an order to proceed with certain work is received (usually from the engineering officer), the work (or part of it) is assigned to an available field party on a work assignment sheet. Figure 14-3 shows the type of information entered on a typical work assignment sheet.

When field notes have been reduced to the data sought in the survey, this data is set down in an abstract sheet. Typical abstract sheets are bench mark sheets, control point sheets, traverse sheets, and base line sheets.

Figure 14-5.-A control point sheet.

shown in figure 14-5. Traverse and base line sheets give the locations of traverse or base line stations, the latitude and departure of each course or baseline, and the coordinate location of each traverse or base line station. For a traverse sheet or base line sheet, the computational sheet used to compute latitudes, departures, and coordinates usually provides a satisfactory abstract.

You are already familiar with field and office work and therefore realize the ever-present possibility of errors in surveying. As supervisor, you should be aware that a large part of your job is checking to ensure that errors are detected. In the field, as mentioned before, you must keep the measurement situation in hand by ensuring that the measuring methods used are those that reduce the possibility of error to a minimum. For example, when tape corrections are called for, you must ensure that correct tension is applied, that temperatures are taken, and that temperature corrections are applied accurately.

You are also responsible for error-free computations. Obviously, you cannot check all computations by performing all the calculations involved; this would be the equivalent of doing all the computing yourself. You can, however, require computing procedures that will, if they are followed, reveal the existence of errors. For example, you can require that areas be obtained both by double meridian distance and by double parallel distance. There are, of course, numerous other computations in which the use of two methods will give results that can be checked against each other.

Finally, you must develop skill in the weighing of results for the probability of error. This is a skill that cannot be taught; it comes with experience. For example, after you have had a good deal of experience with contour mapping, you develop the ability to get the "feel" of the ground when you study contour lines. This often helps you spot a misdrawn contour line arrangement because the arrangement is inconsistent with real-life probability.