Author Topic: Humminbird 998C why is my position shown on dry land when 1/4 mile offshore  (Read 1744 times)

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Offline guy@oceanacademy.co.uk

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Hi and can someone explain why my boat position is shown on dry land according to the GPS map (actually 200 metres in on an island) when I am 200 < 300 metres offshore? Also when on an inland lake, boat position shown on the land adjoining the lake.

I have always updated the Navionics charts before use. Does the GPS need re-calibrating or some form of setup prior to use?

Thanks


Offline Rüdiger

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Hi Guy

Welcome to the Forum

I know of no adjustment for the GPS function. If your unit only produced for the U.S. market and the software version of your unit?

mvh
Rüdiger
Sorry
English is not my first language !
http://de.groups.yahoo.com/group/SOB-International/

Offline guy@oceanacademy.co.uk

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Hi Rudiger,

I bought my unit from the UK and had it shipped to Malaysia. I am using the Navionics version 1.8.8.0 charts for West Asia, being Malaysia, SIngapore, Thailand etc which update fine.

I am based on a small island 2 miles x 1 mile and have 16 odd waypoints for dive sites, but both the boat and the waypoints on the East coast appear to be on the island. So I am positioned on the waypoint 200 metres offshore, but the display shows me and the waypoint on the island.

This is duplicated on the lake in Kuala Lumpur, I am on the water but the display shows me to be on the land adjacent to the water.

The reason I am trying resolve this I need to map the seabed with the sidescan and need to know that I am getting accurate GPS fixes  before I convert the files for use with Garmin Mapsource. This will allow me to print a map of the seabed.

Many thanks,

Guy

Offline Humminbird_Greg

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Guy,
The GPS positioning and the maps are two different parts.  The GPS can be pin point accurate but the maps could be off.

I would first start by looking at the GPS Diagnostic View and see what the Fix Type is and what the HDOP and Est Pos Error numbers are.

If those look good I would try using the Map Offset feature.

Greg Walters at Humminbird
gwalters@johnsonoutdoors.com

Offline sonar2000

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One other thing I have seen in the past is a map may be in a datum different than the GPS. Possibly because someone changed the unit gps datam. check to make sure both are the same. This alone will do just what you described..
Chuck

Offline guy@oceanacademy.co.uk

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Hi Greg and Sound2000, will check later and advise. thanks Guy


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