Orienteering map

Land forms are shown using contour lines. The contour interval is normally 5 metres, but other interval such as 2 or 2.5 metres may be used in sprint maps. Additional symbols are provided to show e.g. earth bank, knoll, depression, small depression, pit, broken ground etc.

This group covers cliffs, boulders, boulder fields, and boulder clusters etc.

This group covers lakes, ponds, rivers, water channels, marshes, and wells etc.

Vegetation: White colour is forest, yellow is open area, and green indicates reduced runability.

This group covers vegetation. White is typically open runnable forest. Green means a forest of low visibility with reduced running speed, being graded from slow running, through difficult running, to impassable. Yellow colour shows open areas. Green vertical stripes are used to indicate undergrowth (slow or difficult running) but otherwise with good visibility.

Man-made features include roads, tracks, paths, power lines, stone walls, fences, buildings, etc.

Two technical symbols are required on all maps: Magnetic north lines printed in blue, and register crosses (these show that the printed colours are coincident).[2]

Other information is required to be on the printed map although the presentation is not specified, e.g. scale, contour interval and scale bar. Good practice requires information such as date of survey, survey scale, copyright information, and proper credit for the people who produced the map (surveyor, cartographer).

Course

Symbols are specified so that a course can be overprinted on the map. It includes symbols for the start, control points, control numbers, lines between control points, and finish. Extra symbols are available so that information relating to that event may be shown e.g. crossing points, forbidden route, first aid post, and refreshment point etc. These are not permanent features and cannot be included when the map is printed.

The International Specification for Orienteering Maps[2] sets out the specifications for orienteering maps for use in foot orienteering, together with specifications for the other sports governed by the International Orienteering Federation (IOF) i.e. mountain bike orienteering, ski orienteering, and trail orienteering. The specifications are mostly the same but with a few sport specific symbols e.g. ski-o needs to distinguish snow-covered roads from cleared roads.

The base map can be a topographic map made for other purposes e.g. mapping from the National Mapping Agency, or a photogrammetric plot produced from an aerial survey.

As LIDAR-surveying advances, base maps consisting of 1 meter contours and other data derived from the LIDAR data get more common. As these base maps contain large amounts of information the cartographic generalization becomes important in creating a readable map.[4]

Cartographers use a projection to project the curved surface of the earth onto a flat surface. This generates a grid that is used as a base for national topographic mapping. The projection introduces a distortion so that grid north differs from true north; magnetic north is a natural feature that differs from both. As an example: at 52° 35' N 1° 10' E (approx 7 km west of Norwich, England) true north is 2° 33' west of grid north, and magnetic north is about 7° west of grid north. Magnetic north varies continually and in this example (1986) was reducing by about 1⁄2° in four years.[5] Orienteering maps are printed using magnetic north and this requires an adjustment to be made to the base map.

Field-work is carried out using a small part of the base map fixed to a survey board, covered with a piece of draughting film, and drawn with pencils. The final map needs to be drawn with sufficient accuracy so that a feature shown on the map can be identified clearly on the ground by the competitor, thus, field-workers need to locate features with a high level of accuracy, to ensure consistency between map and terrain. Where the map and terrain are inconsistent, the feature becomes unusable: no control point can be placed there. Periodic corrections to the map may be necessary, typically vegetation changes in forested areas.

The earliest orienteering maps used existing topographic maps e.g. United Kingdom Ordnance Survey 1:25 000 plans. These were cut down to a suitable size, corrected by hand, and then copied.

These were initially drawn by hand on tracing paper using one sheet for each of the five colours; the various dot or line screens being added using dry transfer screens, for example Letratone manufactured by Letraset in the UK. The map was drawn at twice final map scale, and photographically reduced to produce the five film positives for printing. This was a simple process that required very few specialist tools. Draughting film has replaced tracing paper. This is a plastic waterproof material etched on one side so that the ink will hold.

This is the standard process used by National Mapping Agencies. It uses a plastic film, which is coated on one side with a photo-opaque film. The layer is removed with a scribing tool or scalpel to produce a negative image. One sheet of film is needed for each solid colour, and one for each screen, usually requiring about ten sheets of film altogether. The map is drawn at final map scale, and the negatives are printed with high quality dot screens to produce the five film positives for printing. The process makes it easy to produce high quality maps, but it does require a number of specialist tools.

Computer software is available to aid in the drawing of digital maps. OCAD is the leading provider. Another one is opensource OpenOrienteering Mapper application, created by community as free alternative to OCAD.[6] Other computer software is available that will link with OCAD, or with the digital map files, so that courses can be incorporated into the map ready for printing.

Colour maps were sent to commercial printers for printing in five colours, with the overprinting being added after the map had been printed. This process was chosen as it gave a higher quality for the fine line-work than the industry standard four-colour process (CMYK). As computer and software technology has advanced, and the cost reduced, many clubs are now in a position to print their own maps. This enables clubs to print the six colours together (map and overprinting symbols) using that same four-colour process, but with a reduction in quality over traditional printing. Printing costs can be minimised by using standard stock sizes of paper e.g. A4 or Letter. It is important to use the correct type of paper: both the weight and the coating affect the usability of the final map.