Ocean Currents 



Mechanical 

 Current Meter 

 (Ekman) 



Speed: 0.15 to 2.5 knots/Ac- 

 curacy: ±0.1 knot 



Direction: to 360 degrees/Ac- 

 curacy: ±10 degrees 



Not continuous or deck-reading 



Electro-M echani- 

 cal Current 

 Meter Types 



Price Meter 



Roberts Meter 

 Mod. 3 



Speed: 0.1 to 6.5 knots/ Ac- 

 curacy: ±0.1 knot 



Direction: None 



Marginal accuracy; mainte- 

 nance problems 



Speed: 0.2 to 7.0 knots/Accura- 

 cy: ±0.1 knot 



Direction : to 360 degrees/Ac- 

 curacy: ±10 degrees 



High threshold level; mainte- 

 nance problems 



Low Velocity 

 Types 



Hytech 

 Crouse-Hinds 



Pruitt 



CM-3 (Japanese) 



Geomagnatic 

 Electro 

 Kinetograph (GEX) 



Speed: 0.1 to 7.0 knots/Accura- 

 cy: ±0.1 knot 



Direction : to 360 degrees/Ac- 

 curacy: ±10 degrees 



Speed: 0.04 to 7.0 knots/Accu- 

 racy: ±0.01 knot 



Direction: to 360 degrees/Ac- 

 curacy: ±10 degrees 



Speed: 0.2 to 5.0 knots/Accura- 

 cy: ±0.1 knot 



Direction: to 360 degrees/Ac- 

 curacy: ± 10 degrees 



Uncertain 



Photographic Type 

 (German paddle 

 wheel) 



Speed: 0.3 to 3.0 knots /Accura- 

 cy: ±0.1 knot 



Direction : to 360 degrees/Ac- 

 curacy: + 10 degrees 



Parachute Drogues 



(Speeds and accuracies deter- 

 mined from two tests by the 

 Hydrographic Office) 



Various methods are being considered for current 

 measurement such as a suspended-drop current 

 meter (Lamont Geological Observatory), the Sa- 

 vonius Rotor, etc., to improve these instruments 

 and their operating limits. Broad design criteria for 

 further new developments have been documented 

 as: A need for a good solid-state type of curient 

 meter design with a speed range of 0.1 to 10.0 

 knots, accuracy: ±0.1 knot (lower thresholds and 

 accuracies desired for special research projects), 

 direction: ± 10 degrees, depth range: unlimited 

 in some designs (but not necessarily for those with 

 the speed ranges, accuracies, and directions men- 

 tioned above), simplicity in over-all design and 

 operation, rugged, minimum maintenance, stand- 

 ardization of output signal range, and stability in 

 three dimensional space. Standardization of out- 

 put signals should be compatible to present ma- 

 chine tabulation and/or computers. 



Drift Bottle 



Crude, slow, and uncertain 



Transparency 

 and Visibility 

 Determinations 



Submarine 

 Photometer 



Depth: Approximately 500 feet 



Hydrophotometer Depth: 200 feet 

 Mark 2 



Secchi Disc 



Depth: 20 feet (maximum) 



An example of a new design is the tele-recording 

 bathypliotometer (Boden, Kampa, & Snodgrass). 

 Sophistications of all these instruments and new de- 

 signs which also assist in the determination of cur- 

 rents and biological conditions should employ auto- 

 matic calibration, an ease of alignment, an ability 

 to determine suspended particles in the ocean (by 

 size, number, and type), an ability to measure at- 

 tenuation of ambient light with depth, capable of 

 transparency measurement in relatively clear open 

 ocean water, have a design simplicity, be capable 

 of measurement of number of wavelengths, and be 

 dependable. 



Density 



No direct measuring No direct measuring device 

 instrument available for continuous meas- 



urements with the accuracy 

 + 10~» desired 



New instruments should not be sensitive to gravity 

 dissolved gases, acceleration and organic matter in 

 sample. Direct, accurate, density measuring sys- 

 tems are being sought. 



Tide 



Portable tide gauge Not bottom mounted, self-con- 

 tained, or unattended 



Nearly all the tide gauges in the U. S. are operated 

 by the U. S. Coast and Geodetic Survey. Systems 

 under consideration and in development include 

 tide-buoy telemetering with output signals appro- 

 priate for computer work. Some advanced design 

 criteria and the problems involved for improved 

 gauges are: accurate determination of a vertical 

 datum, crustal movements, classification of tides 

 affecting different coast lines, attain accuracy of 

 ±0.01 foot, determine parallax and declination 

 cycles, tidal pulsations in deep ocean water, and 

 tidal buildup. 



156 



