Horizontal Control
Traverse is a method in the field of surveying to establish horizontal control networks. Traverse networks involved placing the survey stations along a line or path of travel, and then using the previously surveyed points as a base for observing the next point. Types of traverse are:
: Link traverse
: Polygonal/Loop traverses
: Open/Free traverse
: Close traverse
Vertical Control
Leveling is one of the methods available in surveying for determining heights of points above (or below) an agreed datum, typically mean sea level. When leveling, it is possible to measure heights within a few millimeters and this order of precision is more than adequate for height measurement in the majority of surveying projects. As well as leveling it is worth noting that heights can also be measured by using total stations, handheld laser distance meters and GPS. The equipment required to carry out leveling is an optical, digital or laser level.To control heights at surveyed area, an established temporary bench mark (TBM) required inside or near the surveyed area. TBM needs to be established by fly level from any bench mark found nearby. In surveying a bench mark is specifically any permanent marker placed by a surveyor with a precisely known vertical elevation (but not necessarily a precisely known horizontal location). These reference points may be chiseled into a wall, or more typically, marked by small brass or aluminum disks, iron pins or bolts that are permanently attached to a stable foundation, such as concrete posts, bridge abutments, buildings, or a specifically constructed concrete block. These markers are then used as starting (control) points by subsequent surveyors and other users to establish the elevation of nearby points.
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