Converting British Grid To Lat/long

[Scarybiscuits]

Hi,

Can anyone point me in the direction of a site or programme that will convert British Grid co-ords (in the format posted under the lat/long co-ords on the cache pages, rather than eastings and northings) to Latitude/Longitude and back?

I'm having trouble finding something that will do it using the full set of numbers as used on the geocaching site.

Would be very appreciated!

Thanks

[+wildlifewriter]

Can anyone point me in the direction of a site or programme that will convert British Grid co-ords (in the format posted under the lat/long co-ords on the cache pages, rather than eastings and northings...)

Those ARE eastings and northings

to Latitude/Longitude and back? I'm having trouble finding something that will do it using the full set of numbers as used on the geocaching site.

There is a program available from this site called GridInQuest, which will do that thing with more accuracy that you could need. The program is free but site registration is required. Note that GridInQuest is neither friendly nor easy to use, but it does exactly what it says on the tin.

 

Hth

[+The Wobbly Club]

Hi Take a look at our website there is a free download for converting OSGB to Lat Long the url is The Wobbly Clubs Website Hope it is of some use.

 

Daphne & Colin aka The Wobbly Club

[Scarybiscuits]

They are the same thing? That's made me feel thick! But the progs I've seen don't use the letters - surely the preceeding letter pair is vital?

I'll give the suggestions a go, thanks!

 

Edit: just tried both the suggestions... GridInQuest says co-ords are outside of the defined area when I put them in, and the other prog won't let me enter enough numbers! I've got co-ords in the format TL XXXXX XXXXX where Xs are digits. Am I doing something wrong?

Edited September 4, 2004 by Scarybiscuits

[+Haggis Hunter]

But the progs I've seen don't use the letters - surely the preceeding letter pair is vital?

You're dadgum right they are vital!!

 

The UK is covered by 204 Ordnance Survey 1:50,000 Landranger maps. Each map covers 1,600 Sq. Kms.

Each grid square goes from 00 to 99.

100 grid squares each way is not enough to cover the entire UK, so when you get to 99 the next grid square is going to be 00.

This is where the double letters (otherwise known as the UTM (Universal Transverse Mercator)) come into use, these have to be used to determine which 100,000 block square you are in. So when quoting a grid reference, you must always quote the UTM first.

 

I hope that has solved that part for you.

 

Now as for converting, As I don't know why you want to convert it, have you tried just using your GPS, to British mode. It uses the UTM!!

 

Edit: The UTM can be found in each corner of the map, and where the grid changes from 99 to 00. They are the large blue letters.

Edited September 4, 2004 by Haggis Hunter

[+Teasel]

They are the same thing? That's made me feel thick! But the progs I've seen don't use the letters - surely the preceeding letter pair is vital?

No, you're not being thick! Your initial post was correctly worded. They are not the same thing and there are various subtle differences between them beyond the format in which they are written.

 

The format used on the cache pages is commonly called a "grid reference" and consists of a pair of "grid letters" which identify a 100km square, plus a pair of eastings and northings which identify an area within that grid square. The eastings and northings within the grid square can each consist of any number of digits, though 3 is common for walkers and 5 for geocachers.

 

The OS Grid In Quest software does not convert grid references into lat/long. It, and many other similar converters, instead use "coordinates", which is a format where the full eastings and northings in m are given, without any grid letters. (The grid letters determine the "tens of thousands" digit of the full eastings/northings).

 

Fo, for example:

The grid reference TL13 is a 10km square whose SW corner has coordinates eastings: 510000 northings: 230000

The grid reference TL123345 is a 100m square whose SW corner has coordinates eastings: 512300 northings: 234500

The grid reference TL1234534567 is a 1m square whose SW corner has coordinates eastings: 512345 northings 234567

The grid reference TL12345673456789 is a 1cm square whose SW corner has coordinates eastings: 512345.67 northings 234567.89

 

A good tool for coordinate conversions of all sorts (it can handle both grid references and eastings/northings coordinates) is Waypoint Workbench.

Edited September 4, 2004 by Teasel

[+Teasel]

This is where the double letters (otherwise known as the UTM (Universal Transverse Mercator)) come into use, these have to be used to determine which 100,000 block square you are in. So when quoting a grid reference, you must always quote the UTM first.

Ummm, no I don't think so.

 

UTM is a system for dividing the world up into small chunks, such that a transverse mercator projection in each zone works reasonably well. It is not the same thing as the pair of letters at the start of a grid reference.

[+Haggis Hunter]

This is where the double letters (otherwise known as the UTM (Universal Transverse Mercator)) come into use, these have to be used to determine which 100,000 block square you are in. So when quoting a grid reference, you must always quote the UTM first.

Ummm, no I don't think so.

 

UTM is a system for dividing the world up into small chunks, such that a transverse mercator projection in each zone works reasonably well. It is not the same thing as the pair of letters at the start of a grid reference.

Fair one, I have obviously been taught wrong. So I am certainly not going to argue with you on this one.

Do you or anyone else know what the two letters at the start of the grid reference are called? As I have always believed them to be the UTM, but now I know they are not, and I am curious to their actual name.

[Deego]

The OS just refer to them as "grid letters"

[Scarybiscuits]

Thanks for the info, I understand it a bit better now. I would love to be able to enter the OS Grid co-ords in the 2 letters then two sets of 6 numbers form into my GPSr but I can't work out how to do it. I have a Garmin etrex. I know you can change the map datum field to os british grid or similar but this doesn't seem to change anything - the co-ords I enter in still have to be in lat and long. Am I doing something wrong? Would appreciate further help - thanks!

[Deego]

You need to change the Position format as well from hddd.mm.mmm to british grid. Then change the map datum to Ord Srvy GB

Edited September 6, 2004 by Deego

[+Beds Clangers]

Hi Scarybiscuits,

 

As we owe you a drink I could meet up with you and show you what all the responses are about.

 

Regards

 

Nick (Beds Clangers)

[Scarybiscuits]

Ah ha, think I've got it now! Didn't spot that 'position' field!

Sounds good, Beds Clangers, perhaps we can do a cache together first - unless you've done all of them near here! I'll email you shortly.

 

Scarybiscuits