If you have never used OS coordinates before it is probably advisable to make sure that you are comfortable with how they relate to true north and magnetic north. If you are used to using UTM grid coordinates you shouldn't have any problems, they work pretty much the same way just with different origins. Make sure that you are comfortable with magnetic declination and grid convergence and how to translate a magnetic compass bearing to a map grid bearing. I prefer to use a compass like the Silva 15TD which allows you to dial in a grid to magnetic correction so you don't have to do the maths all the time.

Come to think of it, and it is an important point considering the number of overseas visitors doing the challenge, you do realise that compasses are regional? The magnetic flux in Northern Scotland is not horizontal but has a dip of about 70deg. Compass needles are balanced to take this into account. A compass designed to be used in the southern hemisphere will be very unbalanced in Scotland.

There is one simple rule, you go into the house before you go up the stairs, ie eastings before northings. Traditionally OS grid references are given using a Zone (for example NO) and the three eastings and three northings, that will give a location within a 100m x 100m box. These days with GPS level accuracy of +/-3m it is common to give 8 or 10 figure references. On GPS status, if you select OS Grid as the coordinate system, you will get a 8 digit reference. If you have magnetometers built into your phone GPS status will use those as well which means you have a highly accurate compass and location system combined.
I use GPS status as much for geocaching as I do hill walking.

I've just figured out the OS coordinates, it seems the first site I read wasn't correct, so it had me confused for a while. Until I realized it's just math, X and Y.

When it comes to true north and magnetic north I'm spoiled, being from Sweden. They don't differ much at all. I'm thinking that, upon arrival in Scotland, I'll compare my compass to a gps unit of some kind, and see how much it differs?

I have no clue what UTM grid coordinates are, maybe if I know what it's short for, but it could be something I don't know about as well.

I've found an excellent program for mapping routes, Suunto Movescount, http://www.movescount.com/ There seems to be no way to print your map, at least not without buying Suunto watch, but you can export your route to a gpx-file and import it to a program where you can print it. I intended to import into google maps, but I haven't yet figured out how to do this.

Ulla,
don't worry too much what UTM is, it is simply a way of projecting the surface of the earth, which is a sphere onto a map which is a flat surface. UTM is a grid which covers the whole world, the OS system uses the same projection system but just covers the British Isles. The origin point is out in the Atlantic ocean. Grid North differs to true North because of the projection and the difference varies depending you are. This difference known as convergence is fixed with time.
Magnetic North is also different from true North and the difference, known as declination, changes with time and where you are.
If you have bought a new OS map recently it will have a diagram showing the relationships between the three Norths in the area covered by the map and how they change with time. It is also possible to check online.
http://www.geomag.bgs.ac.uk/data_service/models_compass/gma_calc.html

You need to understand the relationship if you are going to set yourself a bearing to follow using a compass or work out where you are on the map by taking the bearing of two landmarks.

https://www.ordnancesurvey.co.uk/resources/maps-and-geographic-resources/finding-north.html

Hi Ulla

You're getting lots of great advice as usual here. Reading the two parts of your post It looks as if you are happy doing traditional map/compass nav. but want the security of being able see exactly where you are occasionaly using your phone mapping and gps.

Unless you enjoy using tech (or are not so confident with map and compass) I wouldn't bother with route files or waypoints. I'd suggest planning your route online. Take paper maps (or even better printouts on Toughprint paper) and use the OS app on your phone together with the digital mapping that you got access to when you bought the paper maps.

If you don't have all the maps for your route (either digital or paper) you can buy digital mapping quite cheaply. Memory Map sells 1:50000 mapping for the whole of the UK for £60 or you can just buy a smaller amount of data and download the map tiles that you want to your phone. Checking your position from time to time uses very little battery life and can save you from carrying an extra battery or powerpack.

All I do is load load the most critical bits of my route (not just for the Challenge) onto my phone when I have wifi.

Willie

Thanks for your replies. I have a lot to look into when I return home from my mother's house next weekend! Now I just have to decide on the route. Reading challengers' blogs makes me change my mind all the time...