Topographical maps, and the skills needed to read them, are powerful additions to any outdoor enthusiast's toolkit. Not only can these maps help campers and hikers plan their routes and find their way, but they can also add to the safety of a trip by helping people to avoid getting lost and pinpoint their location when needed.
What the wide range of topographical maps out there have in common is that they all represent features of the Earth's surface (or its "topography"). Slopes, for example, are represented by contour lines, and other features such as rivers, lakes, roads, and even buildings can also be represented. Each map has a legend to enable the reader to make sense of its symbols, and a grid (for example UTM, latitude/longitude, or both). Topographical maps differ of course in the areas that they cover and the detail with which they do so. The major factor that determines this level of detail is a map's "scale", and this article will focus on the various scales out there, their descriptions, and which purposes are best served by each.
A map's "scale" refers to the distance that a particular length, on the map itself, corresponds to in "real life. The scale is presented in this form: 1:250000, and will be printed somewhere on the map. Depending on the country in which you obtain the map, these numbers may use different units. For example, in Canada a map with scale 1:50000 means 1 cm on the map corresponds to 50000cm on the ground (or 1cm to 0.5km) (4). An American map that advertises the scale 1:24000 likely means 1 inch corresponds to 24000 inches. This difference in units is important to keep in mind in order to be able to properly read and understand the map.
Various countries also differ when it comes to which maps are produced and in which scales. If you are unsure, some research online can help to shed some light on this, and can even direct you to sources where you can purchase or obtain the maps that you need. The Canadian government, for example, produces 2 scales of topographic map (4). The first has a scale of 1:250000 (cm) and provides a general overview, and the second has a scale of 1:50000 (cm) and provides more detail (5). In the U.S., maps are produced by the U.S. Geological Survey, which offers up a wider variety of scales, for example 1:24000 (1 (1:1.6 mile), 1:250000 (1 (1":1 mile)(2).
Another important aspect of scale on a topographical map is the interval of the contour lines. Topographical maps have lines that represent areas of common altitude, which allows these maps to represent slope in a readable format. The closer the lines are to each other on the map, the steeper the slope in that area. For example, if a line is drawn for every 50m of altitude, you can estimate the slope by counting the lines in a given area on the map using some simple mathematics.
So now that you are familiar with some of the scales out there, how do you know which one you want?When planning your general destination, it makes sense to look at maps with a higher scale ratio as these will give more of a general overview of a larger area. You can look for any features of interest such as rivers or hilly regions. Once you have narrowed down the area of interest, you can then seek out maps with a lower scale ratio as these have greater detail. If you will be on foot (for example hiking) you will want to have a map with lots of detail so that you can use it to orient yourself. You can even use it in conjunction with a compass or GPS system if you like as well. If you would like a detailed map of a larger area that will not fit on one map you can purchase adjacent ones and "fit" them together. No matter which scale you choose, check the date on the map to make sure that it is a recent one.
Maps can help hikers and campers make the most of their trips by helping them plan their trips, navigate effectively while on the ground, and stay safe by knowing their locations. With the advancement of mapping and GPS technology in recent years, maps are a tool that is accessible to anyone with an interest in using them.
Sources:
1)http://en.wikipedia.org/wiki/Topograp hic_map
2)http://erg.usgs.gov/isb/pubs/booklets/topo/ topo.html
3)http://www.gpsnuts.com/myGPS/GPS/Tutorial s/Maps/maps.htm
4)http://maps.nrcan.gc.ca
5)http://www .fedpubs.com/topographic.htm
1)http://www.abc-of-hiki ng.com/navigation-skills/maps.asp