Calibration

[cookiegee]

Hi All,
new to forum, and need help regarding My Garmin GPS Map 396 unit is showing false positioning ie; I am in ocean and it is showing me as on land, not by much but still by a couple 100 mtrs off, any ideas please

 

[Nuvi-Nebie]

I think the best way forward is to determin if the error is due to positioning or mapping, I would start by getting a Latitude / Longitude position from the 396 and enter it into a on-line mapping system like Google Earth to determin whether it ties up with where you were, if if does the 396 position is correct and may be that the map data for your location is incorrect

Some GPSs have a setting called Position Format >> Map Datum, changing this can make small shifts in the relation between Lat/Long position and map position, the default (in the UK) is WGS84 but there may be a better local one, e.g. Aus Geod '84

 

[cookiegee]

Thanks Nuvi, I will give that a go, I believe position is correct as my fishing marks are spot on so maybe it is the map doing strange stuff, I will also take another GPS with me and try that, thanks again.
Cooky

 

[Nuvi-Nebie]

Garmin units intended for land use are not very good when it comes to areas of water, they only show the coast which obviously move with the tides, so I wouldn't expect accuracy, marine GPSs are supplied with Bluecharts specifically for sea areas

 

[cookiegee]

Thanks for reply, I have had this GPS for 10 years and have never had this problem, in fact I have given wrong model previously , It should read GPS map 276c, I do have Bluechart in unit, All the marks are correct but it seems the map has moved as per photo, got me stumped, The island should be about 800mtrs to the right