Twist and Turn Posted June 18, 2003 Share Posted June 18, 2003 Hi there, I just purchased a Garmin Etrex and OS 1:25 000 scale maps of my local area but the co-ordinates on the GPS don't match up with the OS map (well not clearly, there are Lon/Lat markings on the far outside of the map but no grid lines). If it is not a silly question why do you use the hddd mm mmm & WGS 84 format instead of the OS grid format for finding caches? Twister Quote Link to comment
Twist and Turn Posted June 18, 2003 Author Share Posted June 18, 2003 Oops, I also meant to ask, is there a UK map series that shows lon/lat grid lines instead of OS grid references, preferably at 1:25 000 scale? Twister Quote Link to comment
MCL Posted June 18, 2003 Share Posted June 18, 2003 quote:Originally posted by Twist and Turn: If it is not a silly question why do you use the hddd mm mmm & WGS 84 format instead of the OS grid format for finding caches? Twister It's not a silly question, and the answer is that Geocaching is a global activity which requires a global standard. Hence the sport has adopted WGS84 (becuase that's the native co-ordinate datum of the GPS network) and Lat/Long. as to exactly why the numeric format was chosen, I don't know, and I suspect maybe no-one does now. It was probably a case of settling with the first option that one of the founders' own GPS reciever happened to be set to. Unless anyone else knows different? Anyway, it is most definitely not possible to use OS grid co-ordinates anywhere else on the planet except here in the UK, which makes our local system, wonderfuil though it may be, a bit of a global nono. No trees were harmed during the production of this posting, but a large number of electrons were terribly inconvenienced.... Quote Link to comment
+Lizzzzeeeee Posted June 18, 2003 Share Posted June 18, 2003 Hi Twist & Turn, I find myself switching my GPS between hddd mm.mmm and OS grid formats all the time - in fact I'm quite quick at it now. If you're doing a multi-part cache you'll find all the clues and coordinates are in hddd mm.mmm format but to give you an idea of where to go (I don't find the maps on my GPS as user friendly as a nice paper OS map) I need to plot the OS grid ref that my GPS converts for me on the map. I've done it so much now I find it part of the fun!!!! Strange that I am!!!! Lizzzzzzzzzzzzzzeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee Why is it that when you're out for a walk carrying a map everyone asks if you're lost? Quote Link to comment
+Pharisee Posted June 19, 2003 Share Posted June 19, 2003 Like most people, for hunting caches I use the HDDD MM.MMM WGS84 system. For trig points, however, I use the OS 1:25,000 maps and switch my Legend over to the OS grid system. It only takes a couple of clicks on the button and when you're looking at a map and then at the GPSr it makes it much easier to see exactly where you are. It's not that important around the 'Home Counties' where I live as there are always easy landmarks to give you some guidance but it's a different matter if you're half way up a mountain in the Scottish highlands, looking for an easier route to the top John Age and treachery will always triumph over youth and ability. Quote Link to comment
+washboy Posted June 19, 2003 Share Posted June 19, 2003 quote:Originally posted by Liz Codd:I find myself switching my GPS between hddd mm.mmm and OS grid formats all the time Presumably you not only change from hddd mm.mmm to OS grid but also from WGS84 to OSGB? Otherwise, you'll be somewhat "offset". ===== There's no such thing as a free lunchbox! Quote Link to comment
+Pharisee Posted June 19, 2003 Share Posted June 19, 2003 quote:Originally posted by washboy: quote:Originally posted by Liz Codd:I find myself switching my GPS between hddd mm.mmm and OS grid formats all the time Presumably you not only change from hddd mm.mmm to OS grid but also from WGS84 to OSGB? Otherwise, you'll be somewhat "offset". ===== _There's no such thing as a free lunchbox!_ I'm not sure about the 'lesser' members of the Etrex family but with my Legend, if you select 'British Grid' as the Position Format the Map Datum automatically changes to 'Ord Srvy GB'. Likewise if you select 'hddd mm.mmm' as the Position Format it changes the Map Datum to 'WGS 84'. However... if you change the Map Datum manually, the Position Format is NOT automatically changed. John Age and treachery will always triumph over youth and ability. Quote Link to comment
+John Stead Posted June 19, 2003 Share Posted June 19, 2003 With my Vista switching the position format from hddd^ mm.mmm' to British Grid automatically selects OSGB datum and vice versa, so presumably others in the eTrex range and probably other ranges do so as well. Member Geocaching Association of GB Quote Link to comment
+Pharisee Posted June 19, 2003 Share Posted June 19, 2003 Hee hee... beat ya by a minute John Age and treachery will always triumph over youth and ability. Quote Link to comment
+John Stead Posted June 19, 2003 Share Posted June 19, 2003 Woops, John Pharisee and JohnStead are telepathic. Nice to know others are wasting time at this time of day - we should be out caching! Member Geocaching Association of GB Quote Link to comment
+John Stead Posted June 19, 2003 Share Posted June 19, 2003 You are too quick for me - and I only came on to see how OMally is getting on, then realized that that it another forum! Try this http://www.gagb.org.uk/forum/index.php?act=ST&f=2&t=54 Member Geocaching Association of GB Quote Link to comment
Twist and Turn Posted June 19, 2003 Author Share Posted June 19, 2003 Thanks for all the info, very helpfull. Incidently, I've tried switching the position format in my Etrex (basic model) and it doesn't change the Map datum at the same time :-( Never mind, the manual change will keep my thumb fit too! Twister Quote Link to comment
+Naefearjustbeer Posted June 19, 2003 Share Posted June 19, 2003 My basic etrex doesnt do it either I just checked AUT PAX AUT BELLUM Quote Link to comment
+BigBirdNL Posted June 19, 2003 Share Posted June 19, 2003 For maps (OSGB) combined with WGS84 caches, you can use CacheMaps. It supports downloading cache info en show it on several OSGB datum maps at your choice. Datum conversion is done internally and shown with the waypoints if you want. On the download area you can also find a convertor for WGS84 to OSGB. BigBird -- there is no spoon -- Quote Link to comment
MCL Posted June 19, 2003 Share Posted June 19, 2003 [ignore this post. Shame I can't delete it really....] [This message was edited by MCL on June 19, 2003 at 05:03 PM.] Quote Link to comment
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