One of the key capabilities of being a productive angler is to find the best fishing spot.  This could be a reef, rock pile, submerged tree, wreck, ledge, hump, etc.  Even when you have the exact GPS coordinates for a great spot it is often not simple to anchor and fish successfully.    The ability to fish directly on structure is critical to success when targeting certain species such as Blackfish-Tautog and Snappers.  See our article Catching Trophy Tautog for more information on catching big Tog.

The GPS Problem – COG vs. Heading

Sonar/GPS units work very well to find a spot if you have the coordinates.  The built-in topographic maps, relief shading and integration with GPS make this an easy task.  When the boat slows to a stop COG (course over ground) location measurements are no longer accurate.    COG is the measure as the boat moves between current location and previous location to estimate the heading and direction the boat is traveling.  If the boat is not moving COG does not work and the GPS loses track of location. 

If your GPS has an issue with COG, it will be very evident as you locate and then stop on a spot.  The mark/spot will move and spin around on the map as the electronics have lost their ability to recognize the direction the boat is pointing.  This becomes particularly challenging when you try to anchor up current from a spot as the mark moves around on the map display and spins randomly.  The boat will spin around the spot as shown in the image below.

Locating the Exact Fishing Spot

There is a simple solution to the lack of COG accuracy by installing a magnetic heading sensor (digital compass).  Marine electronics packages such as those with autopilot systems already have magnetic heading sensors which are not subject to the COG issues.  If your boat is having the above issues, you can add a heading sensor to the existing NMEA 2000 network.  Once the heading sensor is installed the GPS and boat location will be locked in and not drift or spin as the boat stops moving.

Garmin SteadyCast™ Heading Sensor – $159

Lowrance Point-1 GPS Antenna and Heading Sensor – $199

Simrad GPS25 Antenna – $289

Humminbird GPS Receiver with Heading Sensor – $219

Some heading sensors are cross compatible between manufacturers, so check with your GPS device manual for more information.  Even if a third party sensor is compatible,  it could be more difficult to calibrate unless you have consistency between the sensor and GPS manufacturers.

Sensor Location and Calibration

The heading sensor must be mounted in a location away from ferrous metals (aluminum is ok), magnets and motors on the boat to minimize interference.  Otherwise, the sensor will not work or calibrate properly.  Once mounted in the proper location, the sensor needs to be calibrated to the specific boat configuration.   This process involves driving the boat in a few slow 360 degree circles and then running the boat in a straight line at cruising speeds.  Manufactures, such as Garmin, supply an accuracy rating (0-100) on the calibration session.  If the calibration accuracy is low, you can move the sensor to a different location and recalibrate the device.

SUMMARY

To be a successful angler it is critical to be able to locate and fish on spots that attract trophy fish.  By using your GPS/MFD and a heading sensor you can locate, anchor and fish these spots accurately and with ease.

If you have any suggestions or other ways to find productive fishing spots, please send me a note.  You can contact me by email at [email protected].

Tight lines …  Captain P.