EDM-Height Traversing versus Geodetic Leveling

Abstract

In the past, EDM-height traversing was rarely considered as an alternative to geodetic leveling. This paper outlines the theory of the method and investigates the attainable accuracy. In flat terrain, EDM-height traversing is capable of achieving third-order leveling specifications, while in mountainous areas it can compete even with first-order leveling, if systematic errors of the latter are taken into account. Published results are summarized, and a list of recommended practices is given.

Practical results of EDM-Height traversing

“…;tssumed equal to sin Zji with sufficient accuracy. It can be shown (Brunner, 1975;Rueger & Brunner, 1981) that the height differences obtained from Eq. (2) are fully compatible with height differences obtained by geodetic levelling.…”

“…The height difference h between the trunnion axis of the theodolite and the zero of the staff can be calculated from two zenith angles (z. an~. Z2) to two graduation lines (Q. and Q2) on a levelling staff placed over the bench mark (Rueger & Brunner, 1981).…”

“…(I). Such a height transfer between a station of an EDM-height traverse and a bench mark is accurate to ±0.3 mm if the distance between theodolite and staff does not exceed 30 m (Rueger & Brunner, 1981). …”

“…The observation sequence is thus similar to geodetic (spirit) levelling. Leap-frog EDM-height travers!,ng is not further discussed here because it is considered to be an unsuitable technique (Rueger & Brunner, 1981). The disadvantages of this method are that it requires the measurement of a forward and backward run to provid~ for a check and that the foresight and backsight distances have the same length to within 10 m. This last requirement makes the method very time consuming and is often impossible to achieve in difficult terrain.…”

“…The findings by Rueger & Brunner (1981) are summarized in Table 1. The computed standard deviations of a 1 km EDM-height traverse are based on standard deviations of ±1.0" and ±5.0 mm for zenith angles and slope distances respectively.…”