Total beginner - Lat/Long vs. O.S. Map References

EdF · Occasional Visitor Joined: Oct 10, 2007 Posts: 5

Hi, Just joined the forum as I'm somewhat confused... I bought a cheap GPS device recently (for car route finding - I never use it!), a Fujitsu Siemens Loox which gives lat/long references. Since buying it I've become involved in finding small historical sites and interesting old buildings using public records with map references, to photograph them for the public record (this is encouraged by the Highland Council Archeological Unit). Also, I'm just finding out about geocaching, which sounds interesting (and uses map ref's). So, the Loox lat/long references are not of much use to me, especially as I have no idea how to use them to get a map reference or vice versa. Do I simply have to buy another GPS device which uses O.S. maps and references?? Thanks for any replies.

Border_Collie · Posted: Wed Oct 10, 2007 4:00 pm Post subject:

Does THIS help?

EdF · Occasional Visitor Joined: Oct 10, 2007 Posts: 5

Corrr, many thanks indeed!!!

harryparkes · Occasional Visitor Joined: Sep 17, 2006 Posts: 6

Hi,

The conversion given in the previous reply converts OSGB36 Lat/Long to NGR. My guess is that your GPS gives WGS84 Lat/Long. If so, you will have an error of about 100 metres if you use this converter.

There are a number converters available which will do the job including one from OS at
http://gps.ordnancesurvey.co.uk/convert.asp

However, unless you are really desparate for cash, I suggest that you buy a GPS intended for walkers and which will give OS NGR and are ideal for your intended purpose. A couple of examples are Garmin Etrex and Geko models
Harry

EdF · Occasional Visitor Joined: Oct 10, 2007 Posts: 5

Learning all the time. Thanks Harry.. I don't know all the TLA's yet, but I can guess OSGB, not so sure about WGS84, NGR or the 36 part of OSGB36.. I'll have a look at the Garmin stuff too. Now, where are my old boots...?
If anyone reading my posts in Scotland is interested in locating historical sites as mentioned above, the best Scottish web site (IMHO) is www.rcahms.gov.uk Register and have a look at the 'CANMORE' site link, then zoom in on the map to anywhere in Scotland and the blue dots mark historical sites. There are a LOT! Some may not even be visible any more, others may be castles and anything in between. Click on one and the archive record of it will come up. (You have to click on 'I' on the taskbar under the map to get information, then click on the blue dot). Afraid I don't know of anything similar for the rest of the UK.

philpugh · Posted: Wed Oct 10, 2007 5:47 pm Post subject:

Two are nmemonics for different datums.

GR stands for Grid Reference - which is common to ALL map datums (i.e. the concept of a grid)

If you want to find out about them - nd if you intend using a GPS for 'exploring' then you should be at least a little familiar with them - then I suggest you google for map datums - there are thousands of sites that help.

For now

WGS84 (World Geodetic System 1984) defines a (US view Razz

) of the worlds lat long. It is this that caused the 0 deg LongtitudePrime Merdian to shift a distance away from the famous brass line (Prime Meridian) at Greenwich.

OSGB36 is a short hand for the Airey Datum (again this isn't the full name) defined in 1936 and used since then to be the reference for all OSGB maps in the UK.
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Phil

barryd · Posted: Wed Oct 10, 2007 5:49 pm Post subject:

Hi
If you want to be able to do the conversion on your Loox you could try my free utility OS GPS Convertor that'll let you enter a WGS84 lat & long or an OSGB grid reference and see it converted to the other format. All you would need to do would be to install it and run it, ignoring the rest of the web page that talks about integrating it with other software.

Assuming you're looking at geocaching.com, then all caches worldwide use WGS84 lat/long for their position. For UK cache pages a corresponding OS grid reference is also shown which, like my utility, should be accurate to within 5m. If you get into caching you may want to look at programs for the Pocket PC that let you store databases of caches (I use Cachemate) on your Pocket PC and navigate to them using the GPS, and others you can run on the PC to manage cache information (I use GSAK which is heavily tailored to geocaching but some people also use it to create their own databases of any other location-based information such as monuments) and send it to the Pocket PC.

Those solutions are all very cheap. You could also look at buying OS mapping to put on your Pocket PC from Memory-Map or Anquet or Fugawi, but that soon starts to get expensive for large areas.

Just thought another piece of Pocket PC software that will talk to your GPS and show you your current position in both WGS84 lat/long and OS grid reference is GPS Speed Sentry.
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Barry Davies

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