CODAS+UHDAS Documentation

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Primary heading deviceΒΆ

UH ADCP group recommends using the gyro as the primary heading device.

Reasons: Unless there is a compelling need for highly accurate real-time velocities (i.e. withing 2-3cm/s), UH ADCP recommends gyro as the primary heading (that is much more reliable and will give currents good to 10cm/s). Data can be post-processed to incorporate the better heading source if it was reliable during the cruise, and it’s much easier to do that in post-processing than to fix bad data if the POSMV or Seapath or Ashtech had problems.

This example uses “POSMV” as the gps-derived heading instrument. If ou have Seapath or Ashtech, just substitute names.

-------------------------------------
  Preferred Scenario:
  the gyro goes into the deck unit:
  (only works with ocean surveyor
-------------------------------------


gyro (synchro) --> deck unit
com 1: ADCP
com 2: positions (pcode reciever)      (goes to N1R files)
com 3: POSMV heading                   (goes to N2R files)

- use pcode positions
- use gyro headings as primary headings as the default.


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 Alternative Scenario: the gyro is
 only available as a serial input:
 (or the instrument is a workhorse)
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If gyro is only available as a serial input and we assume data streams directly from the instruments (gyro, posmv, etc), then we use: com 1: ADCP

and for com2 and com3, we are constrained by VmDas requirements. Options are:

com 2 (N1R files) com 3 (N2R files) bonus penalty
posmv positions gyro headings posmv headings in N1R files rely on posmv positions
pcode positions posmv headings
posmv positions
in N2R files
no gyro heading
pcode positions gyro heading better sources
no posmv logged
with VmDAS

If gyro is only a serial input, recommend: - use positions from “other” heading device; - use gyro headings as primary headings as the default.

and then get from ship’s techs, 1/second ascii files logged during the cruise - pcode - gyro - posmv

These are recommendations from Univ. Hawaii ADCP group. We supply open-source software for processing these data, and have software, engineering, and scientific experience with ADCPs, but the installation and data processing are ultimately in the hands of the operators and the scientists.