Introduction to Maps and Map Care
Maps are essential when it comes to navigating in unfamiliar or dangerous terrain, and if we don’t look after them we can put ourselves and others at great risk. This lesson will briefly introduce the concept of what a map is, some of the forms modern maps come in, and outline some things you should do to look after your map. Let’s start with a video (11 minutes long) and then we will recap some of the main points highlighted.
All maps are drawn to scale, the most common we work with being 1:50000 and 1:25000, but what do these numbers mean? Well, a map scale is essentially a ratio. On a 1:50,000 (one to fifty thousand) scale map, each centimetre (cm) on the map equates to 50,000 cm of actual terrain. An easier way to put this into perspective is 1 cm is 500m, so 1 kilometre (km) on the map, will be represented by 2 cm. The scale of a map we chose for our activity will reflect the nature of activity we want to do; driving 50 miles we are unlikely to need the accuracy of a 1:50000 map, but a 1:250000 road map may be more suitable, and equally using a road map to hike the Brecon Beacons would be unadvisable.
Here’s a table of some common scales and their uses:
|Scale||1 cm =||Common Uses|
|1:2,500||25 meters||Urban planning|
|1:25,000||250 meters||Outdoor activities|
|1:50,000||500 meters||Outdoor activities|
|1:100,000||1,000 meters / 1 kilometre||Cycling, backpacking|
|1:250,000||2,500 meters / 2.5 kilometres||Road or cycle trips|
|1:1,000,000||10 kilometres||Map of the UK|
While we would strive to carry a map that contains as much information as possible, this would mean to cover the same area we would need as many as 2 or 4 times as may maps, especially for multi-day hiking routes or cycling tours. Have a look at how some of the different scales of maps may look. Notice how the levels of information contained within them also changes.
As mentioned in the video, the size of grid square also changes depending on the map you use. A 1 cm square on a 1:50,000 map covers an area of 1 square kilometre, but this doubles to 2 cm squares for the same area on a 1:25,000 map. As a rule of thumb, the diagonal distance across a grid square is 1.5 km. The same map area sees an increase of 4 times, resulting in more detailed information, but also the need to carry more maps for the same area.
The two main map products from Ordnance Survey are their Explorer (1:25,000) and Landranger (1:50,000) map series. Each sheet has a name, but also a sheet number. In the example image these are the “Explorer OL2” and “Landranger 110” maps. Each sheet number is part of the larger national grid system in which every part of the country is covered. This grid system is shown below. You can also find maps for your own area using their map finder tool.
Folding a Map
This is an art! But it shouldn’t be complicated. Thankfully most maps we buy will already be folded, but there may be times where we actually want to re-fold a map to reflect an area we will be working in. We’ll start with a fresh map that hasn’t been folded before.
- Roll the map flat, onto a flat surface – the floor or a large table.
- Work out what way you want to fold the map. It is easiest to create the first fold horizontally.
- Fold the map in half, long ways. This will present the map information to the front, and the blank side folded in on itself (unless you have a double sided map, then you will need to chose which side you want to use first).
- Now think about folding the map again, this time short ways.
- With the map folded into quarters, unfold the end and line it up with the edge.
- Now repeat the folds until you have created a concertina.
- You can now open and close the map folds, remembering to flip the map over to see the information contained on the back.
Custom Map Folds
There will be times where having the map folded using the generic method above won’t cover the area you need. Or, like some military training areas, the area we will be working in doesn’t justify having a large folded map on view. What we can do, is create a series of map folds to present only the information we need to hand.
Quite often, these map folds will be told to you as part of the orders process, and will take the form of using the grid lines on the map, such as; “map folds, north 53, south 45, east 09, west 02.”
We’ll look at how we can fold a map to these folds.
- You have identified the area you need to view.
- Your map folds will follow existing grid lines,
- Start to fold the map using these grid lines. The folds may not line up equally with the edge of the map, so repeat the folds as many times as you need to tuck the unused map behind the useful portion.
- Repeat the folding horizontally as well as vertically.
- You now have a map folded to present only the information you need.
Using this method, it will not be as easy to view areas outside your folds, or to reference the marginal information. Consider this before you fold.
Expanding on what was covered in the video, we can look at the rules when dealing with maps. These are to ensure the integrity of any information on the map and to make sure you get long life out of your valuable maps.
- Don’t rely on digital maps and GPS. Batteries die, and signal can be lost. Always carry a well protected, properly folded paper backup.
- Never draw or write directly onto a map. If you must, then use a light pencil that can be erased later.
- When working outdoors, always use a map cover or case. This will protect the map from adverse weather conditions and grubby fingers.
- Never cut a map, you never know when you will need the information you destroy.
- Protect and look after your map. Sometimes it can be your only way out of trouble.
And finally, know how to use your map. As you develop your knowledge you will soon become more comfortable reading a map and using it for navigation. You have now taken your first step into knowing how to use your map.
You can move on to the next activity looking at map symbols. This is an interactive session, and you can take the quiz as many times as you need – Ordnance Survey 1:25,000 map symbols.