Zeiss practical hints concerning traversing 6. Available to purchase for immediate download. Below is an extract from the manual converted to text for a quick impression on the content. Zeiss practical hints concerning traversing 6Practical hints concerning traversing with the 6,561? ft (2m)-subtense barBy measuring the parallactic angle, 7, with the theodolite set up on T, it is possible to measure the distance TB indirectly, in coniunction with the 6.5617 ft. (2 m)-subtense bar set up on B. The computed distance may be the desired length, 5; it may, however, also serve as an auxiliary base, b', for determining a larger distance, s. The geometric figures, which have to be measured in order to get from the 6.56l7ft. (2 m)-subtense bar, b, on to the distance 5, which is to be determined, we call triangle sequences; these triangle sequences are designated as follows: