Geodimeter 140T Auto-Tracking Survey System. 



The Zeiss Elta-2s Electronic Survey System 



The Zeiss Elta-2s Electronic Survey System was used for the profile surveys from June 

 1981 to April 1990 (Figure 5). The Zeiss system incorporates in one compact unit a first- 

 order electronic theodolite, distance meter, microprocessor, rechargeable power supply, and 

 an interchangeable solid state memory module. When optically aimed at a reflecting prism on 

 the CRAB, the instrument uses a collimated infrared beam to measure distance and the 

 electronic theodolite to measure both horizontal and vertical angles. The microprocessor then 

 uses these measurements plus the coordinates of the instrument and the height of the CRAB to 

 compute X, Y, and Z Cartesian coordinates of the ground point under the CRAB (corrected 

 for earth curvature). 



The Zeiss system required about 10 sec to aim, shoot, and record each survey point. The 

 survey of each profile line took about 40 to 50 min, collecting an average of 36 data points. 

 Because the actual coordinates of each point were displayed, the CRAB could easily be kept 

 on line to within + 1.5 m (+5 ft) or better through radio communications between the CRAB 

 driver and the instrument operator. Once the survey was complete, the solid state memory 

 was removed from the Zeiss and the data were transferred through a Zeiss interface to a 

 desktop computer. The survey data were processed with ISRP, the Interactive Survey 

 Reduction Program (Birkemeier 1984). 



A unique feature of the Zeiss system is its ability to accept and record an additional piece 

 of information (up to 7 digits) with every survey point. This feature was used to manually 

 enter the angular tilt of the CRAB, which was measured with two orthogonal tilt meters. Up 



Figure 5. The Zeiss Elta-2s electronic survey instrument 

 Chapter 2 Profile Data 



