MAPPING for ELITE TRAIL-O

Brian Parker (GBR)

The Guidelines associated with the General Rules for Trail Orienteering include a section on mapping.

For elite trail orienteering the mapping guidelines are inadequate and need additional interpretation.

(Since this report was published, at the IOF Trail O Committee meeting on 14th March 2000, it was decided that this standard should be used for all Trail O maps where possible.)

The Guidelines recommend the following:

1.1.1 The map must be an accurate representation of the terrain.

1.1.2 The map scale should be between 1:2000 and 1:10000.

1.1.3 Enlargement of existing orienteering maps by colour photocopying is acceptable.....

Notwithstanding these guidelines, it is unlikely that a standard orienteering map, however well surveyed and drawn, could support trail orienteering at elite level. The main reason for this is that all maps are generalised (simplified) and the level of generalisation required for standard orienteering maps at a scale of 1:15000 eliminates essential detail required for the subtle placing of control flags in elite trail orienteering competition.

An important objective for the elite trail orienteering map is for it to have the same general style and feel as the maps used for elite foot orienteering. Remember that elite competition in both these disciplines demands similar high skills of map reading and terrain interpretation.

Map scales and symbol size for elite trail orienteering

Although the scale of the elite trail orienteering map has to be considerably increased from that for elite foot orienteering, it should not be increased further than is necessary for its elite purpose. The elite trail orienteering map is more detailed but still has significant generalisation.

The increased scale is needed, not only for allowing essential finer detail to be included, but also to allow the control circle position on the map to be better determined and distinguished from other nearby positions. Experience from elite trail orienteering competitions leads to the following recommendation:

Recommended scale for elite trail orienteering   1:5000

For similar reasons to those for the maps enlarged from 15000 scale to 10000 in foot orienteering, the trail orienteering maps have further enlarged symbols. But an increase pro rata to 300% does not allow for the additional necessary detail and gives a map which appears as too crude a representation. Experience suggests that the map symbol enlargement which gives the best legibility and visual balance for an elite 1:5000 map is as follows:

Recommended symbol size for elite trail orienteering   200%

It follows from these considerations that the enlargement by photocopying of existing maps is not acceptable for elite trail orienteering. The map must be specially produced.

N.B. For use at the timed controls, segments of the map enlarged to 1:2500 may be preferred.

See figure showing original scale, enlarged map, and map at recommended scale with recommended symbol size.

Surveying for an elite trail orienteering map

In general the elite trail orienteering map is a modified version of an existing foot orienteering map. Producing an elite trail orienteering map in isolation is not normally economic in terms of both effort and money.

There are two significant advantages in using an existing map. The obvious one is that the existing map, provided it has been well prepared, acts as a reliable base for making the trail orienteering corrections. The other advantage is that the areas not used for the trail orienteering (away from the trail orienteering corridor) are still represented and give the map a complete appearance.

The Mapper's task with the 'base' map to convert it to a trail orienteering map is both to make it more detailed and to make it less detailed. This is not a contradiction in terms!

There is a fundamental difference between trail orienteering mapping and foot orienteering mapping, quite apart from scale and other details. The foot orienteering map is a true plan view which has to be correct when viewed from any position within the map. The trail orienteering map is an oblique view map presented in plan form. It needs to appear correct from a very limited number of oblique viewing points.

The Mapper therefore needs to add or amend detail which appears correct from the viewing positions. Also the Mapper may remove detail that is not visible from the viewing positions, if doing so allows a better representation of the detail which can be seen.

See figure showing enlarged original map, and the map after resurvey around the Trail O control sites.

The recommended working arrangement for producing the elite trail orienteering map is for the Planner to agree the control sites with the Controller, together with the required 'base' map amendments. These are then passed to the Mapper, with on site discussion to confirm the exact details. It is useful if the three official functions of planning, controlling and mapping can be carried out on site at the same time.

Drawing an elite trail orienteering map

With an important exception, the elite trail orienteering map is identical with standard orienteering maps in its representation of terrain.

The difference is that the elite trail orienteering map does not indicate runnability, but visibility. In doing so it uses similar area symbols, but with different interpretation.

The following recommendations are made:

Visibility symbols on trail orienteering maps
Forest: restricted visibility .......... 40% green dot screen
Undergrowth: restricted visibility .......... 33% green vertical line screen
Dense vegetation: very restricted visibility .......... 100% green

In general, the representation of marshes and the various grades of open land or runnability is also a reasonable representation for differences of appearance and no change to these symbols is necessary.

Course representation on the elite trail orienteering map

The Guidelines relevant to drawing the course are:

1.1.4 In all cases the course must be overprinted with start, numbered control circles and finish, all drawn with precision. The correct marker must be in the centre of a 4 or 5 mm circle.

1.1.5 The overprinting of the control number, relevant to the control circle concerned will indicate the direction from which markers should be viewed by being printed on that side of the circle.

1.1.6 Care should be taken to avoid obscuring important information on the map when drawing the circles or adding the numbers.

The precision with which a control flag is positioned in an elite trail orienteering competition may need to be to 1m, or even better. For the map at 1:5000 scale this requires placing of the control circle to 0.2mm, or better.
p>It is therefore strongly recommended that the elite trail orienteering course is produced as an edition of the map and not added later as an overprint, as indicated in the Guidelines.

The course is represented on the map in the same way as with foot orienteering with straight lines drawn between control circles. However, if a single straight line cannot be drawn between successive controls without interfering with the legibility of previous or subsequent controls, then the line may be broken or have changes of direction inserted into it.

The placing of the control numbers may be particularly difficult. The number indicates the 90 degree segment (quadrant) within which the viewing point is located. If the number can be placed on the map behind the viewing point, to the rear of the competitor whilst viewing, then there is no problem. But if the number has to be placed between the viewing point and the control, there may be obscuring of important information.

These potential problems and the high precision with which the course has to be drawn requires more contact between the Mapper and the Controller than is usual.

Printing the elite trail orienteering map

Currently, trail orienteering does not involve large entries, so that the long print runs associated with maps for foot orienteering are not viable.

Fortunately, advancing technology offers acceptable quality at reasonable cost. One successful arrangement is the printing of masters using a desk top machine and then colour photocopying to produce the required number of competition maps.

The competition maps for the British Trail Orienteering Championships in 1998 were produced using OCAD 5 software and printing masters on an inkjet printer at 360 dpi resolution. To improve final resolution quality the masters were printed enlarged by 1.41 then were reduced back to 1.00 (A3 to A4) in the colour photocopier.

Such is the rapid pace of technical improvement that, one year later, the competition maps for the Trail Orienteering World Cup were produced using OCAD 6 software and printing on an inkjet printer at 1440 dpi resolution. Colour photocopying was at actual size.

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