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In oceanography, the sverdrup (symbol: Sv) is a non-SI metric unit of volumetric flow rate, with 1 Sv equal to 1 million cubic metres per second (264,172,052 US gal/s). [1] [2] It is equivalent to the SI derived unit cubic hectometer per second (symbol: hm 3 /s or hm 3 ⋅s −1): 1 Sv is equal to 1 hm 3 /s.
If so, for consistency, the speeds of navigational fluids (ocean currents, tidal streams, river currents and wind speeds) are also measured in knots. Thus, speed over the ground (SOG; ground speed (GS) in aircraft) and rate of progress towards a distant point ("velocity made good", VMG) can also be given in knots.
By precisely measuring the time to travel from the emitter to the receiver, in both directions, the average water speed can be determined between the two points. By using multiple paths, the water velocity can be determined in three dimensions.
The first routine measurements of river flow in England began on the Thames and Lea in the 1880s, [2] and in Scotland on the River Garry in 1913. [3] The national gauging station network was established in its current form by the early 1970s and consists of approximately 1500 flow measurement stations supplemented by a variable number of temporary monitoring sites. [2]
Depending on the mounting, one can distinguish between side-looking, downward- and upward-looking ADCPs. A bottom-mounted ADCP can measure the speed and direction of currents at equal intervals all the way to the surface. Mounted sideways on a wall or bridge piling in rivers or canals, it can measure the current profile from bank to bank.
This is an average measure. For measuring the discharge of a river we need a different method and the most common is the 'area-velocity' method. The area is the cross sectional area across a river and the average velocity across that section needs to be measured for a unit time, commonly a minute.
Measure length of course by using speed of 8.8 knots and converting into nautical miles via the time, speed, and distance scale Step 6. Connect the two ends of the vectors from the current course to the course made good.
Data in units of m 3 ⋅ s −1 are used along the y-axis or vertical axis of a flow hydrograph, which describes the time variation of discharge of a river (the mean velocity multiplied by cross-sectional area). A moderately sized river discharges in the order of 100 m 3 ⋅ s −1.