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Figure 4-1. Reconnaissance survey.

Figure 4-1. Reconnaissance survey.

Tie Lines Surveying

i Figure 4-2. Grid survey reduce the total number of survey line-miles. Maximum recommended tie line spacing is five times survey line spacing. Whenever possible, tie line and survey line spacing should be the same.

4.3.2 Areal Extent of Survey

The areal extent of the survey should be 10 to 25 percent larger than the project area. When laying out the survey lines, it is wise to allow additional area for a run-in and run-out length to allow the vessel to get on course prior to the first fix.

4.3.3 Contour Interval

The contour interval will usually be specified by the sponsor, if not it should be determined by consulting with the sponsor. Table 4-1 gives recommended contour intervals, based on average water depth. The contour interval will have a major effect on the selection of chart scale, survey line spacing, method of navigation, and methods of horizontal and vertical control.

Table 4-1 Recommended Contour Intervals1

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