How To Used Theodolite/EDM Equipment
Theodolite/EDM Topographic Survey
Description:Using EDM instruments and optical or electronic theodolites, locate the positions and elevations of all topographic detail and a sufficient number of additional elevations to enable a representative contour drawing of the selected areas. See sample field notes in Figure D.9.
Equipment:Theodolite, EDM, and one or more pole-mounted reflecting prisms.
Procedure:
• Set the theodolite at a control station (northing. easting, and elevation known), and backlight on another known control station.
• Set an appropriate reference angle (or azimuth) on the horizontal circle (e.g., 0°00'00" or some assigned azimuth).
• Set the height of the reflecting prisms (HR) on the pole equal to the height of the optical center of the theodolite/EDM (Hi).
• Prepare a sketch of the area to be surveyed.
• Begin taking readings on the appropriate points. Entering the data in the field notes (Figure D.9) and entering the shot number in the appropriate spot on the accompanying field-note sketch. Keep shot numbers sequential, perhaps beginning with 1,000. Work is expedited if two prisms are employed. While one prism-holder is walking to the next shot location. The instrument operators can be taking a reading on the other prism-holder.
• When all field shots (horizontal and vertical angles and horizontal distances) have been taken, sight the reference backsight control station again to verify the angle setting; also, verify that the height of the prism is unchanged.
• Reduce the field notes to determine station elevations and course distances, if required.
• Plot the topographic features and elevations at scales.
• Draw contours over the surveyed areas.
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