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.
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.
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.
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.
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.
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.
