Topic: 788 ci di hd GPS

[Sigler]

When I have my screen split (showing the sonar screen and gps screen) the sonar always shows the brush pile before my gps is over it. What could cause this? It seems like they are not working together right, you would think when the boat icon is coming up on the waypoint the brush pile would start coming up at the time. Would a external puck help this?

[George]

Sigler

Nothing wrong with your system.  Take a look at this ---> http://forums.sideimagingsoft.com/index.php?topic=229.msg699#msg699  <---

The two are independent of each other, your sonar will show what is in the immediate area regardless of what the GPS is showing. 

Also, the GPS results vary from time to time it is not as exacting as we would like it to be.  It depends a lot on the positions of the satellites which varies by season and the time of day.

I did not ask, is the brush pile one that you marked earlier or is it on the map?  Either way the GPS will put you in the general area then you may need to locate it.

To give you an example of the GPS reading variable turn on you system just looking at the map with the little boat icon, if you do it for an hour tied to the same location you will see that it looks like the boat is moving all over, the longer you track this the bigger the area gets. 

Your system has a 50 Channel Internal GPS Humminbird's 50-Channel GPS/WAAS receiver, this is as good as it gets.  The only thing an external GPS would benefit is to locate the GPS receiver as close to the transducer as possible (do not think it is worth the expense).

George

[Whistler]

Keep in mind too that your sonar (2d) beam is a cone shape. If you are using the 83kHz transducer your sonar cone is as large in diameter as your depth. So, if your brush pile is in 20 ft of water the front edge of your sonar cone is shooting 10 ft forward of the transducer installation location and will begin to pickup the brush pile before you are directly over the top of it.