2. Distance measuring instruments 



a. Geodimeter 



It appears that a need will exist for either increased range and 

 accuracy in the Model NASM-4 or a decrease in the size of the Model 

 NASM-3. The Model NASM-4 is considered somewhat limited in its 

 performance, and it is felt that a single instrument combining the 

 advantages of these two models would be desirable. 



b. Tellurometer 



Changes already have been made in the tellurometer, and a 

 new, improved, militarized model is available. The reflector has been 

 improved, and a vibrapack has been incorporated into the set itself. 

 However, the power source remains bulky and bothersome. New batteries 

 that are smaller, more powerful, and leakproof are available and have 

 helped somewhat. It is considered that easier (numerical) dial reading 

 and automatic crystal calibration could well make the instrument easier 

 to operate. 



Results were difficult to obtain from the tellurometer during the 

 first months of its operation, and it was felt at the Hydrogrphic Office 

 that the instrument was mostly at fault. However, further use in two 

 years of field work has shown that the results obtained from the instru- 

 ment improve with the greater experience of the operator. Most of 

 the present reports indicate the need for several weeks of training 

 before an operator can get maximum results from the instrument. 



3. Electronic positioning systems 



A number of new, high accuracy, short range systems, such as 

 Hi- Fix by Decca, HYDRO-DIST by Tellurometer, and EMPE by Cubic 

 Corporation, are being put on the market. It is recommended that these 

 systems be studied and evaluated. It is recommended further that 

 better calibration techniques be developed for the long range systems, 

 such as Loran-C. 



The work already done with ranging systems indicates that the 

 limiting factor is the range of adequate reception rather than the 

 system geometry that is the limiting factor with hyperbolic systems. 

 It also is recommended that research be aimed toward developing 

 a precision ranging system that would have ranges on the order of 

 600 to 800 miles or more. 



XV- 13 



