Electromagnetic log

An Electromagnetic Log, sometimes called an "EM Log", measures the speed of a vessel through water.

It operates on the principle that: 1 when a conductor (such as water) passes through an electromagnetic field, a voltage is created and 2 the amount of voltage created increases as the speed of the conductor increases.

The process is

  1. the EM Log creates an electromagnetic field.
  2. a voltage is induced in the water; the magnitude of the voltage varies depending upon the speed of the water flow past the sensor.
  3. the EM Log measures the voltage created and translates this into the vessel's speed through water.

Advantages
  • No moving parts
  • Less affected by sea growth than Pit sword

Disadvantages
  • Salinity and temperature of water affects calibration
  • Measurements affected by boundary layer, (water speed slowed down close to the hull by friction)
  • Provides boat/ship speed relative to water not ground. Current affects accuracy.
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gollark: ```nimproc makeFilePath(basepath, page, filename: string): string = # putting tons of things into one directory may cause issues, so "shard" it into 256 subdirs deterministically let pageHash = getMD5(page) let hashdir = pageHash[0..1] # it is possible that for some reason someone could make two files/pages which normalize to the same thing # but are nevertheless different files # thus, put the hash of the ORIGINAL file/pagename before the shortened version let pagedir = pageHash[2..31] & "-" & normalizeFilename(page) let filenameHash = getMD5(filename) discard existsOrCreateDir(basepath / hashdir) discard existsOrCreateDir(basepath / hashdir / pagedir) basepath / hashdir / pagedir / (filenameHash & "-" & normalizeFilename(filename))```<@319753218592866315> is this ↑
gollark: There might also be a ROT13 button, if I feel like it.
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gollark: Of course it does. It's important to know how susceptible your document is to frequency analysis if enciphered in certain ways.

See also


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