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Garmin question

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Capt. Paul, bought a used boat with a Garmin 178 in it. Here lately if i'm running up the middle of a wide canal, the unit shows me as being almost to the woodline to my right. If in a narrow canal, it shows me being in the woods. Any kind of adjustment that I can make to it, or is this something that would have to be addressed by Garmin? If it makes any difference, the unit is mounted directly behind the walk-thru windshield on the boat.
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GPS SHOWING an ON LAND POSITION rather than ON THE WATER
.

~ Captain Paul's response to: ~ TBOY~

I have seen that sometimes the maps in some units “register” incorrectly when the GPS unit is tracking in north south direction, but are right on when in an west ~ east tracking position. Newer units provide a more up to date frequency of coordinating the maps overlays to the actual GPS position and are able to provide a more accurate rendition of where the GPS position is on the displayed maps. In addition, the newer units use maps that have been updated and are usually more accurate.

First check your unit. You should have the WAAS feature ENABLED and set to WGS 84 DATUM. Secondly, does the unit have supplementary mapping software installed? It would be on a Garmin Data card that is plugged into the card slot located on the front of the unit. If there is no map data card in that slot then you are only using the standard Garmin base map. This base map generally covers the entire US and as such does not show a lot of detail when compared to the supplemental maps that are available which could cause the position error you describe.

The GPSMAP 178 uses ONLY Garmin data cards for accessory mapping software. Newer Garmin units use more common SD or Micro SD memory cards which are available from non Garmin sources. Installing maps in these Garmin data cards, require a Garmin Data Card Programmer. It is specifically designed to accommodate the Garmin Data card. A Garmin programmer MUST be used to write mapping software to the Garmin Data Card.

If your unit is using the supplemental and the settings were as I suggested, and the unit still indicates tracks on the screen maps that are not
Correct, then I suggest that you contact Garmin support at 1-800-800-1020 and ask for assistance.

I know that the distance is disturbing but I have found that there is usually no “cure” for the user to realign the maps to the actual position. It is something that only Garmin could do, but are very reluctant to attempt..

For now, you have the best that is available for your unit. As I said in my seminar, ALWAYS, ALWAYS, supplement the GPS unit with additional maps, a compass and other necessary item to ensure a safe trip.

The Garmin GPSMAP Sounder is no longer listed as an “in production” GPS unit by the Garmin Web site. As such some parts for the unit are not always available. Garmin data cards in 128 MB are still available, but the Garmin Card Programmer is not. An out of warranty repair may cost more than a newer Garmin unit as their bench time starts around $ 150.00 per hour.

The mounting of the unit would not matter unless the antenna, which is located inside the top of the case does NOT have a clear view of the sky OR if the is an electromagnetic or radio interference near the unit which could distort the position being reported by the device.

Check out your unit and let me know how you make out.

~ Captain Paul ~