Convert British Grid Ref to Lat / long

[+MikeGozna]

Hello everyone.

I am very new to geo-caching, but have done quite a bit of letterboxing on Dartmoor in my younger days. Myself and my wife have just taken up walking, letterboxing and now geocaching, (In our old age lol.). What I would like to be able to do is to convert 3 or 4 figure grid references to lat / long co-ordinates and put them into my GPS. This will cut out a load of compass work while getting to the right spot give or take a few metres, then we can start taking bearings to narrow down the exact spot. Would be much quicker.

Sorry this is a bit long winded. My question is a. can this be done, b. How accurate would it be and c. What is the best program, site etc to do it for me.

Thanks in advance for any assistance I can get on this topic.

 

Mike Gozna. and the Mrs.

[+drdick&vick]

Try this site, it says 6,8 or 10 but that should mean 3, 4 or 5.

Worth a try

 

Conversion

Edited November 15, 2008 by DrDick&Vick

[+The Bongtwashes]

If you set your GPS to Ordnance Survey GB as the datum, and British Grid as the position format then you can enter the grid ref you're used to, and then change to WGS84, and Deg/min/decimal min to convert to the coords we use for worldwide geocaching.

[+MikeGozna]

If you set your GPS to Ordnance Survey GB as the datum, and British Grid as the position format then you can enter the grid ref you're used to, and then change to WGS84, and Deg/min/decimal min to convert to the coords we use for worldwide geocaching.

 

Thankyou for that, that will be very usefull.

 

You may be able to help me with another problem I have, as I explained before I am new to caching and have just bought a Garmin Etrex Vista HCx GPS. I also bought the Topo GB maps and installed. The problem is I dont think I am getting the level of detail on the maps I should do, but I have no one or nothing to compare it with, I am not showing any streets or contour lines on any maps. Could you suggest the best settings or a test to see if the maps have installed correctly. So to be a pain (A newbie at 52!! lol)

Thanks in advance.

Edited November 15, 2008 by MikeGozna

[+MikeGozna]

If you set your GPS to Ordnance Survey GB as the datum, and British Grid as the position format then you can enter the grid ref you're used to, and then change to WGS84, and Deg/min/decimal min to convert to the coords we use for worldwide geocaching.

 

Thanks for that.

Edited November 15, 2008 by MikeGozna

[+MikeGozna]

Try this site, it says 6,8 or 10 but that should mean 3, 4 or 5.

Worth a try

 

Conversion

 

Thanks for that. I looked at the conversion tables and they seem ok, although not exact conversions to the co-ords as given in the cache descriptions. I will experiment to see how close they come to on the moors.

Many yards make sore feet, lol

Maybe you could assist with my question as above. thanks

 

Sorry messed up my replies there a bit

[+JeremyR]

Thanks for that. I looked at the conversion tables and they seem ok, although not exact conversions to the co-ords as given in the cache descriptions. I will experiment to see how close they come to on the moors.

Many yards make sore feet, lol

Maybe you could assist with my question as above. thanks

If you want perfect conversions you'll be somewhat disappointed because it's mathematically virtually impossible but you can get very close. The Ordnance Survey have a conversion tool on their website which they claim has an average error margin of just 20cm (on the mainland) it's a bit cumbersome to use though, it only takes Eastings and Northings so you'll have to convert from your OS grid ref before you use it. nearby.org.uk can do that easily.

 

Oh one more thing when using the OS conversion tool, what they call 'ETRS89 Geodetic' is synonymous with the GPS world's WGS'84 datum so don't worry about that.

[+BCNorwich]

The problem is I dont think I am getting the level of detail on the maps I should do, but I have no one or nothing to compare it with, I am not showing any streets or contour lines on any maps. Could you suggest the best settings or a test to see if the maps have installed correctly. So to be a pain (A newbie at 52!! lol)

Thanks in advance.

 

Hello There,

 

Try zooming in, as you get in closer more and more local detail is shown on the map.

 

Regards

Bernard

[+Amberel]

What I would like to be able to do is to convert 3 or 4 figure grid references to lat / long co-ordinates and put them into my GPS. This will cut out a load of compass work while getting to the right spot give or take a few metres, then we can start taking bearings to narrow down the exact spot. Would be much quicker.

Sorry this is a bit long winded. My question is a. can this be done, b. How accurate would it be and c. What is the best program, site etc to do it for me.

Thanks in advance for any assistance I can get on this topic.

If you have a Windows Mobile (Pocket PC) PDA, I have written an application to do this. It converts all ways between lat/long in WGS84 and OSGB datums, OS grid refs in 5 and 6 digit form with and without grid letters, and it projects polar waypoints. It will also read your GPS and give you bearing and distance to the waypoint. You are welcome to a copy if you would like it. Just drop me an email.

 

The accuracy of my program is about 2 feet - it uses the standard Ordnance Survey algorithms. It is considerably more accurate than the conversion on the GS cache pages, which typically have an error of about 20 feet.

 

In answer to your other question about GB Topo map detail on the HCx, go to the Setup / Map / Detail option and ensure it is set to Normal. You should then see all the detail at a zoom of 200 feet or lower. You should see roads, but don't expect the maps to be anything like as good as OS maps - they're not. Really all I would say is that they are better than nothing. You can get alternative (free) maps from an open source mapping project, the coverage is less complete than the Topo maps, but where they do cover, the detail is much better. Unfortunately they don't do routing, which is why I don't use them.

 

Rgds, Andy

Edited November 16, 2008 by Amberel