NavList:

An interest in level and vertical references led me to this paper from the mid-sixties. The author, William S. von Arx, was (is?) a researcher at Woods Hole trying to find accurate mapping for ocean-floor pressures. Since this would have involved accurate knowledge of the sea surface as a datum, he surveys a variety approaches, but I thought the paragraph 'Horizon' on page R271 was particularly interesting for some detailed limitations and benefits of the traditional level reference. Here's the URL:

http://www.aslo.org/lo/toc/vol_10/supplement2/R0265.pdf

There's also interesting information earlier in the paper about how the Sperry Mark 19 Gyrocompass uses electrolytic tilt-sensors and level gyros to integrate a vertical reference, and how that behaves in storm conditions.

There's a reference to the TRANSIT satellite navigation system already working for the US Navy in 1960 and von Arx's GEON system, which is apparently why he knew so much about Sperry Mark 19. Institute of Navigation apparently has the GEON paper from 1964.

Richard Reed

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