Simple handler for fish layback.
How far behind the ship is the fish? This is not always an easy
problem to solve. Hopefully the code here will help out. There are
different methods for different available data.
The Driscoll xstar chirp rev 1 does not have a depth sensor and the
winch does not have a calble counter. Even if it did, not all cable
counters work very well.
Copyright (C) 2005 Kurt Schwehr
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
$Id: layback.py,v 1.2 2005/10/05 19:24:58 schwehr Exp $
Functions |
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- angledepthLayback(fishdepth, cableangle=None, speed=3.5, cableondeck=0.0, gpsoffset=0.0)
- Find the layback if you know the cable angle and fishdepth, but not wireout
fishdepth - meters below sea surface of the fish
cableangle - down angle (plunge) of the wire from the ship to fish (in degrees)
speed - ship speed in knots
cableondeck - distance from winch to block on the a-frame where cable goes down.
make this zero if you zero the winch with the cable out to the a-frame
gpsoffset - distance from gps antenna to the winch.
zero this if the gps knows where the winch is located and make that
the origin of the gps measurements.
returns
layback - meters from the gps measured position to the fish location
- simpleLayback(fishdepth, cableout, cableondeck=0.0, gpsoffset=0.0, cableconst=1.0)
- Calculate a simple layback with know fishdepth and cable out.
fishdepth - meters below sea surface of the fish
cableout - meters of cable out from the winch
cableondeck - distance from winch to block on the a-frame where cable goes down.
make this zero if you zero the winch with the cable out to the a-frame
gpsoffset - distance from gps antenna to the winch.
zero this if the gps knows where the winch is located and make that
the origin of the gps measurements.
cableconst - Some people make this 0.9 to account for wire sag in the water
returns - meters from the gps measured position to the fish location
This code makes all kinds of assumptions.
* The fish is directly behind the boat
* The depth measurement is ok (can be from a sensor or multiple in the data)
* and I am sure there are others
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