Thread: confused!!!!!!

As I understand if you want DI,SI, and 2D from Humminbird or Lowrance you have to also get GPS.Since my lakes are not on it, this seems like an expensive add on. I would think smart companies would see this and make units without this feature.I have a hand held unit and can't see any uses for an additional GPS. You guys may be able to set me straight if I am off base. Also are units with external antennas better than units with built in antennas. I am considering the HB 898 unit with external antenna. since the screen will be a little larger. Comments would be appreciated Thanks everyone for any help......

My $0.02
I would say that most fishermen find GPS useful when combined with the Si sonar. Now with DI or 2D sonar you can always use your handheld GPS to mark the location since you will be directly over the structure you see on your sonar (or very close to it). The Si sonar allows you to see structure from hundreds of feet away. With the GPS combined with the Si sonar you can mark structure you see out to either side 100+ feet away without having to travel over it. This is helpful when you see something but do not have time to run over it and also when someone else is fishing it…

I prefer the external GPS because you can mount the GPS Receiver closer to the transducer which allows you to take some of the position inaccuracy out of your marked waypoint. When you mark a waypoint using sonar (any type of sonar) the unit assumes that the GPS Receiver and the transducer are in the same location. Having them separated by six feet or more could introduce an inaccuracy of up to double that distance. I would want my sonar-GPS system to have the best possible accuracy when marking and traveling back to waypoints, so the external GPS would be the best option here – unless this is for a bow mounted unit in which an internal GPS would be fine (since it would be located close to the trolling motor mounted transducer).