How to Build a Map
Updated: Mar 1, 2019
One of my first jobs in mineral exploration was building maps. I worked with a cartographer to build maps for geologists and became an effective intermediary between the two professions. There are six basic elements required for a good map: coordinates, projection, date, legend, scale and north arrow.
Coordinates are the quantities that define the position of a point on a surface. For geographical maps, the point is represented by two numbers (for a planar map) or three numbers (for a three dimensional map). For a planar map (like a typical road map) the coordinates are usually described as northing and easting for UTM (Universal Transverse Mercator) or north and west for geographical coordinates (latitude and longitude in the western hemisphere-Americas). Ideally, there will be at least four sets of coordinates at equal distances apart to represent the maximum bounds are your area of interest.
A map's projection is is the mathematical transformation of the points on a sphere (the shape of Earth) to the locations on a plane (the shape of a typical map). There are many different styles of transformations that can be used depending where the map is located and how large of an area is represented. A lot of projections will have similar coordinates so it's very important to include the type of projection as a label on the map (and in your data).
The date that the map was created is important in tracking updated and historical versions of the map as well as ensuring the data displayed on the map can be linked to the appropriate data.
The legend(s) on a map help to inform the viewer what the symbols, colours, patterns and lines on the map represent. It is typically in the form of a list with each symbol linked to a word or very short description. If a label was linked to each symbol, the map would become very cluttered and difficult to read.
The relationship of the distance on the map with the actual distance on the surface is called a scale. The scale is typically represented as a bar with segments indicating the actual distance in units (e.g., kilometres, metres, miles or feet) or as a ratio. The ratio does not have units and represents the map size in relation to the actual size, for example 1:20,000 indicates that 1 map unit represents 1 actual unit or 1 cm equals 20,000 cm (i.e., 200 metres) on the ground. As a general rule it is best to use a scale bar on digital maps and a ratio (plus scale bar) on printed maps. For digital maps, the ratio will change if the map is shrunken or expanded to fit within a report.
The majority of the time, north with be located at the top of the map. Occasionally, exceptions are made but it is always best to ensure the reader knows which way is north.
When building a map it is best to follow the design principle noted by the US Navy in 1960, KISS or keep it simple: the idea that simplicity is the key goal in design, and unnecessary complexity is to be avoided.
"It seems that perfection is reached not when there is nothing left to add, but when there is nothing left to take away". Antoine de Saint Exupéry, early 20th century French writer, poet, aristocrat, journalist, and pioneering aviator.
About the Author:
Diana has over 20 years of experience working in the mineral exploration industry searching for diamonds and metals in a range of roles: from heavy minerals lab technician to till sampler, rig geologist, project manager and business owner. Following a Master of Science degree in diamond indicator mineral geochemistry, Diana has conducted field work in BC, NWT, YT, ON (Canada) and in Greenland. She has also been involved, remotely through a BC-based office, on mineral exploration projects located in South America, Africa, Eurasia, and the Middle East. Diana finished a Ph.D. at UNBC in 2017 researching geochemical multivariate statistical analysis and interpretation. Currently, Diana is the owner of Takom Exploration Ltd., a small geological and environmental consulting firm focused on metal exploration in BC and the Yukon.