GPS - A practical guide

This practical guidebook explains how to get the best out of navigating with your GPS, and takes you through GPS navigation in a clear and structured way. It summarises how to navigate with a map and compass. The guide also looks at digital mapping, and how GPSs and mapping software can be used positively together.

CHAPTER 4

Basic Navigation with a GPS

This book is not an A–Z to using your particular make of GPS; they all come with a user guide, and usually a quick start guide too. This should be sufficient to get you navigating round the various screens and menus. I am therefore assuming you have had a good play with your GPS and have set it up for your time zone and grid system, and allowed it to get a fix on your location. This chapter will build on your current knowledge and get you using it properly.

How are you planning to navigate?

How do you navigate yourself round a walk? Do you follow a route from a guidebook or a magazine? Do you photocopy the route (or carry the whole publication), using the sketch map or OS map extract as your sole mapping source? (Hopefully not: all walkers should carry a proper map of the area. What would happen if you strayed off the printed route and therefore off the sketch map?) Do you plan your route assiduously beforehand (possibly using a guidebook as inspiration), filling in a route card or marking your map in some way before you embark on your walk? Or are you a free spirit who decides where to walk on the day?

These three scenarios can all benefit from using a GPS. The guidebook follower can leave his GPS running to record the route; when he starts to wonder where he is he can use the GPS to relocate himself. The route planner can use the GPS alongside digital mapping software to enhance the planning process and transfer the route to the GPS; the free spirit can continue to enjoy his random wanderings, safe in the knowledge that he can relocate himself at any stage of the walk. He can also enter a grid reference as a waypoint should he wish to go to a certain location. We’ll explore these techniques in more detail later.

Where am I?

Stop any GPS user on the hill and ask them how they use their unit. The chances are pretty high you’ll get a response along the lines of ‘Oh I only switch it on when I want to know where I am.’ So let’s deal with this first.

Switch on your unit and wait! If you’ve not had it on for a while it may take a time for the GPS to find and identify the satellites and in turn feed you a location. What that location tells you will depend on how you’ve set up your GPS.

As described in Chapter 3, the UK is covered by a grid system designed to overcome the problems caused by the fact that the earth is a globe and wobbles on its north–south axis from time to time. This artificial grid is known as the OSGB36. Unless you’re a lover of latitude and longitude (and assuming you are in Great Britain), you should ensure your GPS is set to show your location in OSGB or British Grid depending on its make or model. If you’re in Northern or Southern Ireland you’ll need to set your GPS to the Irish Grid.

The location will look something like SK 24345 62787, or maybe SK 24345 N62787 or SK 24345 E 62787 N. In Chapter 3 we covered what these grid letters refer to, but let’s consider the numbers and what the GPS is telling us. You’ll recall that a four-figure grid reference (SK 24 62 using the above example) is only accurate to within a square kilometre, and a six-figure grid reference (SK 243 627) brings us in to an area of 100 x 100m. Adding another digit gets us down to 10 x 10m, and finally the 10-figure reference above is accurate to within 1m.

On the face of it this seems fantastic: we can locate ourselves to within 1m. However, consider this statement on the Ordnance Survey’s website:

Positional accuracy with a single receiver to civilian users approximately equals 5m to 10m, 95 percent of the time, and the height accuracy is generally 15m to 20m, 95 percent of the time.

Even though your GPS is giving a position to within 1m, most of the time it’s 5–10m out. This is pretty good, but let’s consider what even 10m accuracy means on a 1:25,000 map. As we saw in Chapter 3, 1km on the ground is represented by 4cm on the map. This means that 1cm is 250m, 4mm is 100m, and 0.4mm on a map is equivalent to 10m on the ground (an almost impossible distance to measure on the map unless you are at a discrete point such as a stream or wall junction). If 0.4mm is impossible a 10-figure grid reference with 1m accuracy is represented by 0.04mm on the map. Don’t even bother!

Some GPSs give the option of selecting how detailed your grid reference should be. A six-figure reference is adequate, but there’s no need to bother with anything greater than eight.

Once you have this figure, what are you going to do with it? Presumably you switched on your GPS because you weren’t sure where you were in the first place, so once you have your grid reference apply it back to your map.

As Figure 4.2 illustrates GPSs with OS mapping on board are fine to an extent, but you should always refer the location to a paper map as you get a broader overview of your location. But what next? Did the information surprise you? If you have drifted off your planned route, you’ll now need to relocate yourself by working out where you want to be and entering that location as a new waypoint.

Practical exercise
On a short route walk to a feature, identify your grid reference from the GPS. Check it concurs with the feature’s grid reference on the map. Use the Romer on the navigation aid supplied with this book to get an eight-figure grid reference.

Entering a new location

It might sound obvious, but in order to enter a new location you first need to know where you want to go. Even if your GPS has an OS map on-screen, you’re still better referring to the map and calculating a grid reference.

Once you have the grid reference, enter the details into your GPS, select the Go To option and follow the on-screen instructions.

Different GPS receivers require you to go through different steps to enter a new location. My Lowrance iFinder gives me a number of different ways of entering a new location, but I have to edit an existing waymark on my Magellan eXplorist.

Practical exercise
Ensure you know how to enter a new location into your GPS quickly and effectively. Your manual will give you some indication of how to do this, but remember you may be working in poor conditions where speed and accuracy is vital. Identify a number of grid references on a map and enter the details into your GPS. Remember to give each point a unique identifying name you can recognise later.

Getting off-route – and getting back again

The above steps are fine if you aren’t far off-route. However, if you are way off-route then a straight-line route back to your desired location may not be feasible or even safe. A careful study of the map will show you the best options. Figure 4.3 illustrates this point. You have come off the summit of Bleaklow too far south and find yourself at point A, The Pike. However, you need to be over the other side of Yellowslacks Brook at Dog Rock. Entering the coordinates for Dog Rock into the GPS and activating the Go To option will result in you being sent on the direct route indicated by the red line. If you were to head off on the route without referring to the map you’d end up dropping over 80m via a series of crags to the valley floor before an 80m climb out the other side.

The preferable route would be to work your way around the head of the valley as indicated by Figure 4.4. Points C, D and E are all made-up, but were chosen to ensure that the route taken doesn’t drop too far in altitude and that the river is crossed at a point where the wall or fence that runs round the north side of the brook is avoided. Enter the coordinates for the new points into the GPS as new waymark points. Then use the Go To function to navigate from one to the next until you get round to Dog Rock.

Remember If you enter an eight-figure grid reference into a GPS set up for a 10-figure one, put a 0 in the 5th and 10th positions (SK 07550 E 95760 N).

If you are navigating your way round a deep valley as above, accurate grid references aren’t that important. However, you may find it useful to use the scale or Romer on your compass to take a more accurate reference.

Practical exercise
Take a map for a hilly area with which you’re familiar. Select a few deep valleys and try to identify a sensible route round the head of each. Are you using features marked on the map, or are you having to use made-up points?

To help with your confidence in choosing these points, take an area of ground you can wander round freely (it doesn’t have to be a large expanse, but big enough to be able to identify separate grid references). Make a few light pencil marks on the map away from any features. Enter their grid references into your GPS and navigate from one to the next, eventually returning to the starting point. Did you get round OK?

Using your GPS with a map

The above example illustrates why solely using a GPS is not a good idea. Always use it in conjunction with a map. This will ensure you always have an overview of where you are within the wider landscape. Keep referring to the surrounding hills and other major landscape features (invaluable should the GPS fail on you totally or start giving inaccurate readings). Never believe a grid reference without checking it fits with the information on the map and on the ground. It’s very easy to believe technology, especially as it gives us answers so easily!

Creating a route

The steps you went through to negotiate around the valley in the above example is the first step towards creating a route. Most walkers will think about the route in advance, even if only to work out where to park the car, and in which direction to leave the car park. Plotting your route into your GPS before you start would seem like a sensible way of using it.

The other more free-form way of route planning is to do it on the fly, and there’s a whole host of reasons why you might want to do this. Perhaps you’re a wanderer who makes decisions about where to go as the spirit takes you; maybe you planned a route that you want to extend; the weather might have changed for the worse and you decide to curtail your previously planned route to get off the hill sooner. Whatever the reasons and location the steps are identical.

1. First decide where you want to go. Study the map carefully and choose a suitable route that fulfils your aims.
2. Break down the route into suitable legs or sections.
3. Note the grid reference for the start of each section and your end point.
4. Enter each grid reference as a waypoint in your GPS, giving each point a suitable name or consecutive number (names are preferable).
5. Enter the New Route section of your GPS and enter the waypoints in the order you wish to walk them.
6. Save the route and give it a suitable name.
7. Check your waypoints again in case you entered any points incorrectly. Edit any if necessary.

Entering a new route on the go is a time-consuming process. You have to enter the grid reference and give the location a meaningful name (at the very least). If you have to make a comprehensive readjustment to your route you’re in for quite a delay to your walk. If you’re with a small group of mates who are happy to wait that’s fine, but if you’re in charge of a bunch of less experienced walkers who are relying on your navigation and leadership skills then you’re going to have a disgruntled group to deal with. Alternative or emergency routes are discussed in Chapter 5.

The first three steps above are the initial steps of constructing a paper route card (see Figure 5.4, Chapter 5). Along with the height climbed, the horizontal distance for each section and an estimation of the time it’ll take to walk, the route card provides a very useful summary of a day’s walk.

Navigating a route

You’ve entered your planned route – now you have to follow it! Most GPS units have a few different screens that will guide you around your route. Most walkers will probably use the Map screen, which shows the track to take and will also trace your walked route. The other possibility is the Track or Navigation screen which will show you graphically and in figures your bearing or track. Your GPS may also have an electronic compass which will show the direction in which to head to arrive at your intended location. Which screen you use is determined by what’s available on your GPS and personal preference.

You can also choose how to follow your GPS on the ground:

1. Continuously referring to the screen and following the route ‘exactly’.
2. Occasionally referring to the screen and walking in a broad direction.

1 Continuous reference
Once you have entered your route, the GPS will give you the directions to the next waypoint. By continuously referring to the screen try to keep on the desired course until you reach it. It doesn’t matter if you wander slightly off course as you’ll be redirected until you are back on route.

Remember the GPS is trying to work to an accuracy of 1m, but the grid reference you’ll have taken off the map will only be accurate up to 10m at best. Keep in mind what you’re heading for, so that when you get close to the destination you can spot it on the ground.

2 Using your GPS to give you a broad direction
Your GPS will indicate the direction you need to head in. Look ahead in this direction (similar to how you would look along the DOT arrow of a compass) and identify a feature broadly in the direction you’re heading. Walk to this object (you don’t need to keep an eye on your GPS continuously; pop it in a pocket or just hold it in your hand). When you’ve arrived at your feature, repeat the process until you reach your desired location.

Your destination will presumably be an identifiable feature, like a stream junction, or meeting point of two walls or a large rock outcrop. As in the previous example, remember what you’re looking for and don’t rely on your GPS to guide you in exactly to the point. Use your eyes and common sense.

If you’re following a compass bearing and wander off course you may be in danger of missing your intended target especially if you are navigating in bad weather. Using a GPS avoids this possibility. The GPS will continually update your position and alter the information on screen to get you to the desired location.
However, be careful how your GPS tells you that you have reached your location. Many will tell you that you’ve got there before you actually have and, if you’re following a route, will want to send you to your next location automatically. One GPS I used recently moved  me on to my next location 100m short of my destination. That’s fine in theory, but I like to walk to known features and viewpoints. My GPS was preventing me from doing so unless I remained on the ball and continued onto my viewpoint manually. On investigation in the set-up menu I discovered I could adjust the ‘accuracy’ of the arrival alarm which I have subsequently done down to 10m.

Before we progress, let’s consider these two very different methods. The first demands your constant attention on the GPS; the second requires occasional reference plus a regard for your surroundings and destination.

The ‘continuous reference method’ can result in you divorcing yourself from the landscape through which you are walking. You’ll become much more concerned with following the on-screen route and less concerned with where you are. Good navigation is about being aware of where you are within a landscape and less concerned with your exact location at any particular moment. Staring at the GPS screen will mean you take your attention off the bigger picture. On a more prosaic level, if your attention is on the screen you won’t notice where you’re putting your feet and will end up flat on your face very quickly – I’ve done it!

The second method avoids these problems. You’re spotting a broad direction and can then concentrate on finding the best route to get to your intended destination. And you can enjoy the views, have a conversation with your friends and have that valuable thinking time that many of us enjoy when walking. Only when you’re drawing nearer to your destination do you have to concentrate more closely on your navigation.

I use my GPS when teaching groups to navigate with map and compass. I set them a destination for a particular route, enter the location into my GPS and set off with them. I can then wander about the moors concentrating on the group and their needs rather than worrying about the direction in which I’m walking. I know the GPS will get me back on track if necessary.

Practical exercise

1. Plan a route. Enter the waypoints into your GPS, giving each a sensible name or at least a sequential number. Then head for the hills! At your starting point find the first waypoint, tell your GPS to Go To it, and set off. Once there, head for the next waypoint and so on, until you’ve completed your first GPS walk. Don’t forget your map and continually refer back to it, so you know precisely where you are. Don’t forget to analyse the walk at the end. Was it successful? Did you see the features you were hoping to? Did the GPS behave and did you identify any little wrinkles that you need to sort out before your next walk?
2. Take your GPS out onto the hill with a companion, and ask him to identify features on the ground you can navigate to. If he keeps the final destination a secret and you can correctly navigate to it by GPS you’re doing well.