Garmin Nav Setup Confusion

[60North]

I have owned my Garmin GPS2+ for some years and there is something that I don't understand about it, which was highlighted on a recent geocaching trip within the UK.

 

I decided to use the 10 figure grid reference at the top of the geocaching page. Both my son and I fed this into our Garmin GPS'. We also took along paper maps.

 

When we arrived at the car park my son put his GPS into GOTO mode, with the geocache grid ref selected. I had already looked at the map and had envisaged a move away from the car park in a certain direction, but he was heading off at 90 degrees to what I had intended. I followed him, putting my GPS into GOTO mode, with the same grid ref selected.

 

When we arrived at the location that both of the GPS said we should have been heading for we were on the wrong side of the hill and about a third of a mile away according to the map. I took the matter in hand and map read to the location manually. There was a lot of ground clutter with no obvious landmark so we headed back to the car park and changed our GPS' nav setup to: -

 

hddd (degrees) mm.mmm

 

then punched in the location given in that format on the geocache page. This time we used the GOTO function and the arrow took us to where we were when I had manually map read. This time, with more confidence, we searched and found the cache.

 

Our GPS' are set up the same now: -

 

Posn - hddd (degrees) mm.mmm

Datum - WGS 84

CDI Scale - +/- 0.25

Units - Statute

Heading - Auto Mag W006

 

I have read and re-read the manual and other than the last setting, which I am not sure is relevant to this problem anyway, I am sure that these settings are correct.

 

Needless to say, until I find an answer I am going to stick to hddd (degrees) mm.mmm, but as I use OSGB paper maps I really would prefer to use grid references.

 

Any advise would be gladly accepted.

 

Thanks

 

Andy Hayes

[60North]

Its probably bad etiquette to answer your own messages, but at least if I tell you theanswer, I wont appear as dim as when I asked the question.

 

I was using the following settings originally on my Garmin2+

 

POSN - British Grid

Datum - WGS84

 

I should have been using

 

POSN - British Grid

Datum - Ord Srvy GB

 

Doh, doh doh!

 

Now when I look at the GPS and then look at the map, guess what? You guessed it, the GPS gives me the correct grid reference!

 

Andy