North Australian FISH FINDER TM forums

Ae there factors of design or specification which affect GPS accuracy between brands?

I have a Navman (something or other model) combined GPS / sounder and it seems that whenever I try to locate GPS marks, I rarely land straight on top of them whereas my mates cheaper Eagle unit gets us much closer-quicker. As we often fish together and switch between boats, this difference in accuracy has been noted several times on the same markers?

Does anyone have a deeper understanding of what may cause this or whether it's is just luck /conditions on the day?

Are you both going to 3 decimal places? I know that most marks are usually only approximate but if you guys are using the exact same lat/long then that shouldnt be a factor. All I can suggest is that your unit might not be tracking aswell as your mates. I know yours is more expensive but sometimes you just never know. There could also be a multitude of problems that might be causing Db loss from the antenna to the unit, hence might be finding it harder to track correctly

I dont think I helped

I have run Garmin, Lowrance and Humminbird units on the console at the same time and they were all pretty much the same.

Could be any number of reasons why they are different, but the difference should not be great.

I suspect that it may be the location of the antennae.....it is on the gunwal (flush) however the struts from the canopy run alongside and may be blocking reception from some angles...could this be an issue?

Had a navman in the p/mover in Cairns..Used to tell me to turn left halfway up the Gillies Range...into the rockwall ..or over a 1000ft drop.. Couldn't find any explanation from IT bods, so I ditched it. The hand held Garmin in the boat was fairly accurate tho'. Maybe some of the IT savvy blokes on here can sort it for you mate, might just need a setup tweak.

Had 2 Garmins on the boat in the harbour the other day both locked in on the same wreck and one came up with a 300ft discrepency
That was the old ETREX and an ETREX 10
Had me totally intercoursed

There are a few things that maybe causing a difference in position from one Gps to another and it is all due to the settings of the GPS.
The first question I have is " how far out are the marks from one to another Uncle D"?

some causes maybe, Is datum set. Are you both using the same one? This can have a huge difference,
and was mentioned above are you going to 3 decimal points or just 2. ie 12 21 345 or 12 21 34. This will make minimal difference but a difference all the same.

The second is a accuracy setting. This allows you to zoom into a different range. Ie one setting allows you to zoom into 20m screens and another only zooms into 50m screens ect. This will mean that the marks are the same but the screen that you zoom into isnt as accurate giving the appearance that the vessel is on the mark when it is not.

Some Gps have a setting for the location or type of vessel the Gps is installed into. Ie a sailboat, centre console, or forward cabin. This shouldnt make much differnece in a tinny but you never know.

You should be able to go into a screen to check the satillite accuracy and number of satillites being tracked at any time. This will tell you if your antena is reading correctly or not. If not might pay to move it to a higher or clearer position from the canopy poles.

These are just some things to look at.