Map Distortions

Most people in the Western world would readily recognise the coastal outline of the United States or of the United Kingdom. We are happy to ignore the fact that these outlines are gross simplifications of the true coastal outline – even if we have given any thought to what a coastal outline actually represents. Is it the permanently dry bits, and average line between high and low tides or is it another arbitrary line? Line simplification is a necessary function of scale – we are used to the fact that different scale maps represent features with greater and lesser degrees of detail.

We could construct a new map of, say, our locality/research site and base it upon our own measurements taken from a single “datum” point or line. In effect, do our own survey and record the results in the form of a map. In practice, we will often base a new map upon an existing co-ordinate system or upon some existing and trusted reference map. Most maps and co-ordinate systems are “flat” representations of part of the surface of the Earth – a roughly global planet. The representation of a curved surface using a flat map has to introduce some distortion of it’s own. The process of mapping a curved surface onto a plane is known as creating a projection.

As well as the overall distortion introduced by a specific projection we also have to contend with the fact that (at a local level) the Earth does not have a smooth surface. It has hills, mountains and valleys. The distance you might have to trek between two mountain peaks could be very different to the scale difference between them on a map. Few printed maps are capable of representing surface distances accurately across even mildly undulating countryside. Perhaps three dimensional electronic maps will become a feature of our lives in the future but for the moment we have to rely upon our human interpretation of contour lines and other map features to judge distance over the ground.

So what are we playing at with these selective collections of distortions and simplifications we call maps? It just so happens that maps are an amazingly powerful media for transferring knowledge and information between human beings. We at Adit Limited spend a lot of time working with individuals and organisations with specific concern and responsibility for the environment. All of these individuals and organisation make extensive use of maps and mapping tools such as AditMap to record, plan and report on their areas of research and stewardship.

Many people are aware of the fascination of detailed maps such as the UK Ordnance Survey Landranger series or my own local Institut Geographique National 1:25000 maps in France. These maps provide a detailed documentation of an area and even it’s history. You can take a stroll in your mind from village to ancient monument to river bank. You can learn about and visualise a place you have not yet visited, just by reading a map.