The Map and Compass - Navigation For the Hill _ Using Ordnance Survey and Compass Skills on Dartmoor

Hi folks, I'm Seamus from Outdoors Inspiration. This is my German shepherd Petra and today we're going to have a little look at navigation. Today England's currently in lockdown so it'd be prudent that I pointed out that I am taking my daily exercise whilst producing this video and I've walked from my house from the front door so there's no unnecessary travel involved and I'm not hanging about. So the map I'm going to be using today is an Ordnance Survey OL28, that's the Explorer Series Outdoor Leisure 28. That's the map for Dartmoor. It's a 1 in 25,000 scale map. Other cartographers and scales of map also available. I'm not going to go into the ins and outs of projections, I mean we could do that, Mercator, transverse Mercator, nomic projections, but to be honest with you there are far better websites that will explain that for you if that's your back and that's what you want to know. And I'm not going to show you how to derive a six or eight figure grid reference. There are some outstanding websites that can demonstrate that really really well, predominantly the Ordnance Survey website and their education page. I will put a link to that in the description below. That's a really good point of reference if you want to start out with a map and understand what the Ordnance Survey grid is. But I will follow this up with further hints, tips and tricks. We'll do a night session perhaps and look at night navigation and I will bolster this with more information. This is a bit of a taster and some bite-sized chunks. Bear with me, let's see how it goes. Good girl, come on then. So I started off by saying that this map was a 1 in 25,000 scale. I'll just put that in real terms for you. So that means every 25 meters on the ground is represented by one millimeter on the map. Now that presents the mapmaker with a bit of a problem because there's many features on the ground that may occur within that 25 meters and they can't include everything. So here's a top tip. Number one, if it's on the ground it may not necessarily be on the map. Now a really good example of that is perhaps a depression or a raise in altitude of less than 10 meters. If your contours are at 10 meter intervals and a contour on a map is the brown line that represents areas of equal altitude, if they're at 10 meter intervals and gaps on the map and there's a depression in the ground that's only, shall we say, 9.9 meters deep, it won't necessarily be represented on the map. So the mapmakers tend to include as many features as they can to make the map a realistic representation of what's on the ground and by adding features, in the case of an outdoor leisure map, that are useful to the hill walker and hiker. What's on the map is very likely to be on the ground. So I'm looking for this point here which is marked as a cairn. I know what a cairn looks like. It's a big pile of rocks. You get it on the summit of a mountain. The map says I've got it here somewhere. Piles of rocks. So this is actually our cairn and this is a prehistoric cairn ring. It's marked as a cairn on the map. It's actually a curved ring which surrounded a bronze age burial. It is probably 4,000 years old. There is no cairn associated with it, just the ring. Other things that may not be apparent straight away are things like linear features such as walls or fences. They may have been there for, I don't know, a century and they've been removed. But there's generally some sort of evidence on the ground that they've been there. And I don't know if you can make it out but where Petra is right now is a slightly raised lump in the ground, a very longitudinal line in the ground. It runs up here and that's actually marked on the map as a wall as part of the bronze age settlement. Like I said, sometimes things are marked on a map but you may not recognise them for what they are immediately. I prefer Ordnance Survey, Outdoor Leisure, one in 25,000 scale maps. BMC produce maps in one in 40,000 scale as do Harvey's. Ordnance Survey also produce one in 50,000 scale maps. The maps that I use, I always get laminated maps and that's for a very good reason. They get wet and they're more durable and by durable I mean that they can withstand some punishment. So a laminated map can also be marked up and written on. This is an OHP marker, permanent, so I'm going to put a grid reference on there. It's an emergency SX723157. It will come straight off when I get home when I rub it down with a bit of alcohol and I'm not referring to the 12-year-old single malt in the cabinet in the kitchen, I'm referring to the hand sanitiser that I'm carrying with me. It'll take that clean off and leave no mark at all. So let's have a wander up to the top of Hart Hall. Looks like I might need some of those navigation skills to get home. Now just as important as the map is the compass, if not more so. My preferred compass for walking and hiking is a straightforward silver marching compass type 54. This part we generally refer to as the base plate. It has three scales on the Roma, one for one in 25,000, one for 50,000 and one for one in 40,000. The arrows that move with inside this bezel here are the north arrows and this arrow is the direction of travel arrow. And on the outer rotating bezel the compass has 360 degrees marked. And finally there's a needle. That's a magnetic needle that points north. Now I'd like to say that it always points north but they don't always. Generally speaking the needle will point to north. However there are occasions when a compass can reverse polarity. It doesn't happen very often and the needle is actually pointed in the opposite direction and on one occasion it just kind of, it was just kind of vaguely pointing in any direction it become demagnetized. It's quite rare for it to happen but I dealt with a lot of compasses in my lifetime and if you send them back to silver, if it's a silver compass, they will remagnetize it for you. And another problem that can occur with compasses is an air bubble. This is trapped air. I can't do anything about that. I can't get it out. If it's within so many years of its life silver will replace or fix it free of charge. And they will ask you for a couple of letters off the back of the base plate here which denote the year of manufacture and if it's within that, I think it's within five years, they'll certainly repair it for you. There are two other letters on the back of the base plate as well and on this one it says MN, Magnetic North. There are three different compass needle weightings. This is Magnetic North for use in the northern hemisphere. There's a Magnetic South, MS, and one that is intended for equatorial use. So if I'm stood in the southern hemisphere and I've got a compass that's weighted for the northern hemisphere, effectively north is down there. It's not over there so the needle is trying to bury itself. So they're magnetized for different regions in different ways. However if you're in the UK and you're purchasing a compass from a reputable outdoor stockist, it will be a Magnetic North compass. You don't need to check that. Other compasses you may come across are the Ranger type silver compass. And so this one has a mirror for sighting with. This helps me to take a more accurate bearing. This also has a clinometer so if I rotate this if you watch it there's a little arrow that's just here and it's going to sink down and that's for measuring the gradient of hills with. And last but by no means least is my sighting compass. I absolutely love this. It looks like a type 54 standard base plate compass from the outside but it actually has an additional sighting element to it here and that's given me a very accurate reading in the direction in which that's looking. But for today I'm just going to use the standard silver marching compass with a standard base plate. My favourite compass. Now I mentioned that our compass has a needle on it that points to north. It's magnetized so it is going to point to Magnetic North. However Magnetic North is not necessarily at the true point at the top of the earth as my lunch will now demonstrate. So what we actually have is true north and true north is where lines of longitude meet. There we go we've got latitude and longitude on our little globe. But lines of longitude and latitude don't really live on an ordnance survey map. They can be found in smaller data on the map but in all practicality we don't really use them to navigate on an ordnance survey map and nor do we use true north. So if I now represent the United Kingdom on my lunch, there we go, the ordnance survey has effectively laid a grid. 500 kilometre squares which are called the military grid and within that they're broken down into smaller 100 kilometre squares which are the ordnance survey grid and from that we can derive our position on an ordnance survey map using these grid lines as our reference point. But their north depends where you are on that map and they may not necessarily line up with true north. So as I said we don't use true north when we're navigating with ordnance survey we use grid north. But how does that fit in with our compass? Well the compass as I said points towards magnetic north and I'm going to represent magnetic north with this button and I'll stick a corresponding one down here for the magnetic south pole. So depending where you are on the globe these different norths may line up or they may not line up. If I was sailing my ship for example here true north would be there on my chart whereas magnetic north would be over there and there is a variation between the two and very rarely will all three of these ever line up. However I've represented magnetic north by using this sort of general area of the flower and that's because magnetic north the magnetic poles are continuously moving and they move at a predictable rate and that rate of change is called secular change and secular change is predictable. So provided you know when a map was printed and you have the information on that map from the legend you can calculate the difference between where your compass is going to point and your map is pointing and allow a variation or declination between the two. That's an adjustment we can make. So here we go within the legend of the map it's going to tell me information about the north points we've got magnetic north grid north and true north represented as a diagram here and the information on how to calculate the difference is contained here and it'll tell me on the map the date the map was printed and the date for when this was valid and how to apply the change incrementally for each year. Now when I was a youngster my dad taught me how to navigate and apply these variations to the map and the compass. The variation then or declination as his proper name is was seven and a half degrees but for here today because of that secular change on Dartmoor the change is as close to So happy days I don't have to apply anything at all. And you might very well ask what's the point of all that? Well the point is that if I know where north is I can rotate this map I can orientate it in a direction so that it relates to the landscape. I can then transfer bearings from my compass on things that I see on the landscape back to the map and from things on the map that I want to achieve or walk to to my compass to point me in the right direction. And doing that setting a map is a very simple affair to achieve. So first of all I want to line up all the north arrows on my compass. I'm just going to line up north the north arrows on the compass with the direction of travel arrow and as you can see I've got north lined up with the direction of travel arrow and I'm going to place it onto the map. And now I'm going to align the compass with these blue grid lines that run from the top to the bottom of my map. So now that I have them lined up the only thing that isn't lined up is the magnetic needle. So if I rotate myself the compass and the map all together and face in the direction until all the arrows line up you see now that the magnetic needle is lined up with everything else the map is orientated in a way that I can relate to the landscape. And so from here I can see there's a place called North Hessery Tor with a television mast and I'm stood here at Heart Tor. So if I look in this direction now I should be able to see North Hessery Tor. And provided I keep the map set in this manner I should be able to look around me at the landscape and relate to all of those features surrounding me. And you'll find at the bottom of an Ordnance Survey map the scale of the map along with measurements in kilometres, feet and miles. I mentioned the Roma scale on the edge of the compass and for the 1 in 25,000 scale that's this one here we can see that if I place it between two of the lines you'll see that it goes up in increments. It's actually 50 metres, 100, 150, 200 all the way to one kilometre. So we can actually measure distance using the Roma scale. So for example if we're stood at this point on this track and we want to get to this point where the road crosses this spring or this stream we can place the edge of our compass against there with using the correct scale of course and we can measure that and we can see it's approximately 600 metres. So how can I make the map and the compass work for me to determine my position? So there's certainly techniques like triangulation or resection, transferred position lines and various other methodologies which of course doesn't exclude pulling your GPS or phone out to find out where you are. But for the purposes of a simple video I'm going to show you one technique so that you can fix your position if you have a rough idea where you are. And right now I know that I'm somewhere along the banks of the Hartoor Brook. I just don't know exactly where but I can see off in the distance here Hartoor itself. So I'm going to take my compass and I'm going to point it directly at the point that I want to take my bearing on and that in this case is Hartoor. And now I'm going to rotate this bezel on my compass until the north arrows on the compass line up with the magnetic needle and I keep the direction of travel pointing at the point I'm trying to take the bearing from. And this is telling me that Hartoor bears from me 340 that's 350 there so it's 346 degrees from my location. Now keeping the direction of travel arrow pointing in the same direction because this is relative from me to the point that I'm looking at, if I now place the compass on top of the map and I rotate the compass, not the bezel, just the compass until the north arrows on the compass, that's these ones, not the magnetic arrow. Forget the magnetic arrow at this point. Magnetic lives on the compass when you're looking at things out in the open. It doesn't live on a map. These are the ones I'm interested in here and I want to line them up with the lines on the map. We then slide the compass over the point that we've taken the bearing from bearing in mind the direction of travel is pointing in the same direction and follow that line back to the Hartoor Brook where I know I'm stood somewhere on it and now I know I'm at this point here on the Hartoor Brook. So we've actually fixed our position. Now I'm sat on a place called Hartoor and I want to travel to the bottom of this stone row here where it meets the Meavey River. Visibility's looking a bit poor and I want to travel on a compass bearing to that point. I'm going to place the edge of the compass between Hartoor where I'm stood and the destination where I want to go to. I'm going to line the two up so there's the destination point, there's my starting point and they're lined up now. So I rotate the bezel on the compass until the north arrow on the compass and the lines on the compass line up with these blue lines. They're all lined up there and that is my direction of travel from Hartoor to the stone row where it meets the Meavey River and I'm going to physically move my body and turn around until the magnetic needle falls between the compass north needles there and that now gives me my direction of travel. I'm not just going to travel in that direction without taking account of what I pass on the way so let's tick off points as we go. So in terms of ticking off features we've got the stone row marked, there are cairns marked on here as well so we should see something there and they should happen before I hit that river. And fantastic, this is a Bronze Age burial cairn. We know we're heading in the right direction, we've ticked that one off and so lining up our bearing again and we can also tick off a double stone row. It's starting to get dark out here now, the car lights are on, I can see them in the distance and this is the one time I've been out making a video and I'm not worried that it's going to get dark if I'm making a navigation video and I'm worried that it's going to get dark then I'm probably on the wrong subject matter and as promised at the base of the stone row where the river Meavey cuts through here. Come on then onwards and upwards good girl. So the grid lines on an ordnance survey map one in 25,000 scale are four centimetres apart and remember that one millimetre on that map represents 25 metres on the ground. In terms of 25 metres that's usually about the length of the average swimming pool isn't it? But we're not going to get very far if we keep measuring 25 metres in the So a more useful unit of measurement is probably the 100 metres and how do we gauge 100 metres? Think football pitch from one goal to the other. Well I can look off in the distance and sort of imagine where a football field might be but it isn't particularly helpful particularly at night because I won't be able to see anything so I need to be able to measure that and we can do that by pacing and this is an activity during lockdown while you're taking your exercise you can undertake go to a standard football field and measure the amount of paces on average do it three four five times it takes you to walk from one end to the other and by pace it's a double pace. On this occasion I'm going to measure with my right foot and one and two three four five six seven eight. Now I know through years of practice and experience of pacing that I perform 63 double paces to the 100 metres. That will vary depending on terrain whether you're going uphill downhill and technical terrain but you will get a feel for it and you will be able to adjust but it does take practice. So I mentioned earlier that this compass has three scales on it three romas and there's one for one in 25,000 one for one in 50,000 and one for one in 40,000 and the one I want to focus on is the one in 25,000 scale which is the scale of this map so each one of these increments here the tiny increments of 50 metres 100 metres 200 metres 400 600 all the way up to a kilometre here. So if I measure between this wall here and this wall here using the scale on my compass I can see it's 200 metres. So now it's getting dark and I want to know where I'm going at every step of the way so I'm going to pace that 200 metres so this time I'm going to pace 100 metres and I'm going to put a thumb or a finger into the belt of my rucksack and when I get to 200 metres I can put a second finger into the belt of my rucksack or if it was 300 metres 400 metres fingers can go into the belt of my rucksack alternatively many people like to pick up small pebbles and they might pick up say a half a dozen and they'll transfer one from one pocket to the next pocket whatever floats your boat really I'm not an advocate for anything in particular just an advocate for what suits me for what I'm doing in the places where I go with the stuff that I've got. So let's pace our 200 metres shall we and 4 and 5 and 9 and 10 11 61 62 63 that's the first 100 metres 61 62 63 so I should be at the wall now and there we have it so yeah a couple of paces out as you can see Petra's got her flashing light on now so I can tell where she is but I know exactly where I am in relation to my map at this moment in time so what was the point of all that pacing about then well if we know where we started on the map and we know what direction we were travelling in from our compass and we know how far we've travelled that means at any one point we can have an approximation of where we are now but pacing isn't the last word on average I think on rough terrain I probably only walk at about four kilometres per hour so if I'm travelling on a bearing for one hour I've probably covered four kilometres so right now I'm at a place called Crambertal on that point and I want to walk to this OS trig point over here at a spot height of 445 metres and I'm going to measure that with and it's telling me that it's 850 metres so at four kilometres an hour one kilometre would take me 15 minutes 850 metres should take me less than that so I'm going to estimate about 12 minutes to get there that's just rough calculation off the top of my head any longer than 15 minutes and I've probably missed the point so what I'm going to do is I'm going to take a bearing as we did before off the map between the two points and line up the north arrows on the compass now I've got a bearing to walk on I'm going to time myself so if I've been walking for six minutes I know I'm only halfway there if I walk the 12 minutes I'm probably there let's time our journey and walk on a compass bearing there's our trig point 12 minutes and nine seconds 12 minutes and nine seconds so that wasn't a bad estimation at all it's almost as though I've done that before so all of these navigation skills need to be practiced but after a while with a certain amount of practice some things will become intuitive you'll realise how fast you're travelling and how long it will take you to get to particular points what I would say is trying to hit a trig point in restricted visibility or at night over a 900 meter stretch like that you'd be lucky to hit it because you are going to have some deviation in the direction in which you're walking and some people find it difficult to walk on a compass bearing you know I've got friends who couldn't hit a cow's arse with a banjo let alone a trig point at 900 meters so look out for catching features break the segment up into smaller parcels look for elements to tick off and other things that may tell you that you're going astray are the fact that this is at the highest point I pointed out that it's at a a spot height so if I started walking downhill in one direction or downhill in the other direction then I know I'm not really going in the right direction here we are at 445 meters at this trig point here and I want to navigate my way to this point here which is marked BS boundary stone I hasten to add and the boundary stone by the looks thing is just the other side of this linear feature here this black line which from local knowledge I know is a wall and you can actually use the magnifying glass on your compass to enhance the features that are there what happens if my bearing is slightly off or I walk slightly off if I walk in this direction I'll miss the boundary stone and I won't know that I've missed I won't know which part of the wall I'm on but rather than run the risk of missing it why don't I just aim off for somewhere to one side of it so that I can be sure that I know that I've landed on this side so if I take a bearing from the trig point and aim off just south of the boundary stone I know I've got a short walk uphill and then I'll meet it rather than run the risk of missing it completely this skill is called aiming off and I can see that there's a track running here so that's what we call a catching feature so as I walk as I hit that track I know I've gone far enough I can also measure the distance and have a rough estimation of how long that's going to take me and that's my direction we're going to walk in except I'll walk around the big puddle the trig points were put here by the ordnance survey when mapping the area they're a set pattern and design there aren't too many on Dartmoor but you find them all over the countryside normally on high points and spot heights anyway I don't want to lose focus back to my compass come on Petra onwards and upwards oh that's great she can leap it I just get wet feet walking on the bearing I've aimed off south of the boundary stone I want to find and I've got this catching feature in front of me now a track so no boundary stone here that wasn't the intention but what I do know is that I can turn left now and as predicted we're on a slight downward gradient downhill from the the boundary stone and it should be just up here by about 200 meters behind a wall let's go see if we can find it come on Petra onwards and upwards there we go if you remember from the map there was a kink or bend in that wall here it is and you may or may not notice that the the boundary stone's on the wrong side of the wall we said it was on the other side of the wall didn't we that's because that's not it that's the boundary stone there good girl sit clever girl clever girl well thank you for watching so far folks as I said a lot of these skills are things you really need to practice if you've not done them before in a place of safety somewhere that you're familiar with I'll be honest with you this wasn't the easiest of videos to put together so I hope it comes out okay and there are reasons for that because really these are practical skills that you need to practice in reality and do time and time again and you can do that on the hill with somebody who's experienced with you guiding and mentoring or you can go to a safe area and expand on your skills expand that envelope of knowledge and capability as you go along what I do know is that I've enjoyed walking for a couple of days and for a night with Petra to put this together and I hope you have enjoyed it if you do enjoy what we've done with the video perhaps you might have a look at one or two of our other videos as well and what would really be the icing on the cake is if you subscribe to the channel I'd really appreciate followers and I'd be really flattered if you wanted to follow our progress thank you ever so much folks we're going to head for home now so stay safe look after one another and we'll see you all very soon come on then Petra almost an upwards good girl come on then