Questions on GPS

[McSpadden]

Hi Guys,

Went out again Friday to try and find some waypoints, maybe get a snapper or grouper. Well this darn GPS of mine, it is a handheld Garmin Legend, will point me in the right direction then as I get within a hundred feet, moving real slow, at some point the distance to mark starts counting up again as If I had passed the waypoint. I could understand if I had gotten within a couple of feet but it will do in at over a hundred feet from target, every time. Am I experiencing the 7 second lag? Do I need to come to a complete stop then ease towards the mark? I am beginning to wonder if I have a defective unit.

I had been plannin on buying better electronics but something came up with a rental property and so the new stuff will have to be delayed for awhile. That being the case I would like to make do with what I have.

 

[PileDriver]

Just a couple of quick questions and suggestions. I am assuming you are attemping to hit the artifical reef system over there in the pandlehand of FL? If so, under water marks can be a pain depending on the size of the reef and the detail of your sounding (fishfinder) unit. Also, it depends on the acturacy of your GPS unit. Couple of thing you could try, first is in the bay, drop a bouy, or use a channel marker of some kind. Mark the spot on your GPS and then leave the area and let the GPS lead you back. If it takes you right back to the spot, then unit is working ok. If not then it is defective. If the unit is working ok, two things could be occuring, one the GPS waypoints are not as acturate as they could be, hence go to the location and working in a circle, starting from the center letting yourself get wider and wider with each circle, by watching your fishfinder, you should spot the reef. If you still cant find it, it may be the fishfinder itself, or a setting on it. But I really think it is the accuracy of the waypoints more then anything.

Good Luck
Piledriver

 

[McSpadden]

PileDriver would this explain how the GPS itself is acting? It seems awfully strange that it will count down the distance, then from as far out as 100+ feet the distance will begin to increase. I do like your idea of doing a test in the bay and will do it next time I am out. Thanks

 

[PileDriver]

Yes this would occur, the GPS is finding the waypoint but depending on how detailed the waypoint is and the accuracy of the GPS unit, a combination of the two can occur. For example there is a wreck at N29 49.178 W86 16.044 or about 38 nautical miles on a heading of 238 degrees from the Panama City inlet (good for amberjacks and BeeLiners). Just for reference in your area, every tenth on the waypoint equals approximately 50 feet. This changes depending on your location on the globe, but holds true for most of the northern gulf waters. Hence if you could be plus or minus 50 feet if you are only entering a way point to the tenth's position. So for example in the above referenced wreck, if you entered N29 49.17 W86 16.04 you could completely miss it. Now add on top of this, a accuracy of a GPS of plus or minus 25 feet (not sure what the expections of your hand held is) you could off plus or minus 75 feet. Without a bouy marking a reef or wreck it can be difficult to hit.

Hope this helps
Piledriver

 

[MolarBoater]

I use the Legend as a backup in the ditchbag since it is waterproof. You can also use BlueCharts with it and upload all your stored reefs and trips when or if you upgrade to a larger Garmin.

Thanks PileDriver for the detailed info.

I've rarely found reefs exactly where they are printed on the map or online listing. You have to start from the waypt and work your way around in a slow spiraling fashion and still sometimes you'll never find the reef. Many were moved, destroyed or covered with sand by Ivan/Katrina.

When you "confirm" the waypt of a reef, make sure to note the waypt with a special icon or something and delete the old number if it was inaccurate.

 

[McSpadden]

PileDriver,

Thanks for the information. From what you are saying I am pretty sure that I am off that tenth, I wondered when I loaded these waypoints why they did not have the same number of digits. Then only sites I have are public and charted and I figured I would spend time this summer learning all the basics. Thanks again.


Dave