Revision of the International Specification for Orienteering Maps 2000
By Andreas Dresen, , Head of the "ISOM 2000 Project Team" of the IOF Map Committee (Jan 2000)

bal07.gif - -416528,0 K 1 Introduction
The revised International Specification for Orienteering Maps (ISOM 2000) came into force on 1st January 2000. This paper sketches the development of the ISOM from the first attempts at a uniform representation up to the present day and discusses both the major changes and the background to the decisions of the International Orienteering Federation's Map Committee (IOF-MC).

2 History and development of drawing specifications
The first orienteering events were conducted on the basis of the official topographic maps of the respective countries. The scale varied from 1:20,000 to 1:50,000 and the content of the map was determined by the particular type of terrain found in the country concerned. The older generation of present-day runners will recall that such maps were often full of mistakes and out-of-date. In particular, there was often no information about the runnability of the terrain. Chance played a large part in all decisions and fair competitions were almost impossible.
Under these circumstances the call soon came for standardised competition maps paying due regard to the particular requirements of orienteering. In the first national attempts in the sixties corrections and runnability information were added to the basic topographical maps. At the IOF level in the mid-sixties an expert group prepared proposals for representing the terrain on orienteering maps, these were summarised and presented in a "first draft" in 1967.

ISOM 1969
The first issue of the ISOM was ratified by the IOF-Congress in Doksy, CSSR in 1969. This issue was still not a "specification" but rather a "guideline", although it already contained quite concrete requirements. The most important specifications were the scales (1:20,000 and 1:25,000) and the colours

  • ˇ black, brown and blue for topography,
  • ˇ yellow for open ground, and
  • ˇ grey or green / black for restricted runnability (vegetation).
A good example of a map meeting the new specification was the 1970 World Championship Map in the DDR.

ISOM 1975
The second issue of the ISOM was prepared in 1975. This was the first binding specification for maps to be used in international competitions. This version used various well-established specifications from the official topographic representations used in Scandinavia. In comparison with the first ISOM the symbols were organised into the five logical groups still used today and the following changes were made:

  • ˇ scale: 1:20,000 or 1:15,000,
  • ˇ green in three shades for the representation of restricted runnability due to vegetation,
  • ˇ yellow screen or diagonal stripes for semi-open terrain (clearings and felled areas),
  • ˇ grey for bare rock.
In addition to symbols for course setting a total of 100 symbols was defined.

The ISOM 1975 was a compromise between the very different interests and requirements of the IOF member federations. This is particularly obvious in the separation of

  • ˇ "A symbols", which were compulsory,
  • ˇ 25 "B symbols", which could be used according to the special needs of the different types of terrain, and
  • ˇ not closer defined C symbols, "which supplement classes A and B according to the particular conditions of individual types of terrain and are only to be used for national competitions".
The B symbols included, for example, such important symbols as that for a crossable fence or a wall.

ISOM 1982
The third issue of the ISOM was a systematic further development of ISOM 1975 with the aim of consolidating the established and eliminating weaknesses. The number of symbols (excluding symbols for course setting) was almost unchanged at 98. The major changes were:

  • ˇ scale: 1:15,000 or 1:10,000,
  • ˇ introduction of yellow screens to extend the possibilities for combining colours and thus better representing vegetation and runnability,
  • ˇ green stripes to represent restricted runnability with good visibility,
  • ˇ changed print colours brown, yellow and green.

ISOM 1990
The fourth issue of ISOM could build on the foundation of almost 20 years experience of map drawing for Foot-O. It was appropriate to discontinue the distinction between A and B symbols and to abandon the C symbols dating from the early, experimental phase. The established B symbols were incorporated into the list of definitive symbols, which thus grew slightly to 105 symbols.
In summary, the 30 year development of the IOSM may be described as follows:
  • ˇ from a "guideline" to a "rule set" by continuous improvement of colours and symbols on the basis of extensive tests and studies,
  • ˇ increased scale from 1:40,000 Ţ1:25,000 Ţ1: 20,000 Ţ1:15,000 Ţ1:10,000,
  • ˇ extension of the time between revisions from 6 years via 7 and 8 to 10 years.

3 Current status of Drawing Specifications 1999
After almost 30 years development the question may be posed, what has been achieved and what should future development be.

What is ISOM today?
ISOM 1990 is generally recognised as an almost perfect standard for Foot-O. It is also:

  • ˇ a reliable basis for a fair competition,
  • ˇ a clear message to organisers of the expected standard of the map,
  • ˇ a clear message to athletes what to expect of the map in order to prepare for the competition, and - last but not least -
  • ˇ a set of rules with wide acceptance among competitors and IOF member federations.

What can't ISOM be?
A set of rules should only contain the required rules and these should be adequately concrete and precisely defined. In order not to lose clarity, the ISOM should be brief and clearly structured. As a specification for the preparation of orienteering maps the ISOM cannot be simultaneously a manual for teaching map making. In the opinion of the IOF Map Committee this is the role of the "Instructor's Kit" - an instruction manual for the field-work, drawing and printing O maps with numerous illustrations and examples on a CD-ROM. Despite this, a few important explanatory notes are given to facilitate understanding the ISOM.
As part of the competition rules ISOM is not a playground for experimentation. New or changed symbols or colours should not be used in national and international champion-ships or ranking events, but only in local events.

Why change ISOM 1990?
A good product can still be improved. The ISOM 1990 are influenced by manual drawing techniques with ink or scribing. The wide-spread use of computer mapping now permits completely new drawing and printing techniques. In addition to Foot-O - which is still the major form - the IOF has also added new forms of orienteering to its programme. These new possibilities and challenges obviously have to be incorporated into the ISOM. In the last few years it also became clear that some rules of ISOM 1990 which permitted a certain discretion were being used by map-drawers for experiments which were not desirable in international IOF-events. The revision of the ISOM has thus the following aims:

  • ˇ existing standards to be adjusted for computer mapping,
  • ˇ consideration of new printing methods,
  • ˇ inclusion of other forms of orienteering,
  • ˇ stop misusing ISOM for experiments in IOF-competitions.

Map Committee policy
In the last years the IOF Map Committee has received a large number of suggestions for changes. Most of these were small changes, clarifications or extensions. Despite the large number of proposed changes it was obvious that there was no need for significant, major changes. In agreement with the majority of the proposed changes the IOF Map Committee has thus decided to avoid a revolution in the appearance of O-maps, such as was seen in 1975 or 1982. The background to this decision was:
  • ˇ competitors and map-makers are very familiar with the provisions of ISOM 1990,
  • ˇ major changes need a long time for implementation and world-wide training,
  • ˇ investments in existing maps should be protected,
  • ˇ the professionalism and serious nature of the sport at the elite level should not be jeopardised.
However: despite this conservative stand-point the Mapping Committee should be sensitive to new trends and disciplines.

4 Changes in ISOM 2000

4.1 Adjustment to digital cartography
Variations in line widths when O-maps were drawn by hand were generally limited because of the availability of standardised tools such as Rapidograph pens or scribing tools. On the other hand, very fine lines were often somewhat wider than the standard because of the ink running. Thicker lines were of variable width, according to the skill of the individual map drawer. The use of fine screens was also problematic since very fine dots could disappear in the course of repeated copying (negative - positive - printing plate).
Using digital cartography, variations of symbols, line widths and screens are limited only by printing limitations. This permits saying goodbye to traditional techniques. However, exact compliance with norms which is possible today also has the undesirable result that lines with a width of 0.125 mm are often only poorly visible on the printed map. This has led to the following changes in ISOM 2000:

  • ˇ broadening the width of the thin line from 0.125 to 0.14 mm. On the printed map this corresponds to the usual appearance when drawn using a 0.125 mm ink pen,
  • ˇ standardising of line widths at 0.14, 0.16, 0.18, 0.25 and 0.35 mm.
There was no need to define a line width at the 1/1000 mm level.
  • ˇ increasing the ruling in screen definitions from 40 lines/cm to 60 lines/cm.
Because of the denser lines and smaller screen dots the screen appearance is finer so that point- and line-symbols within the screen area are more legible.
  • ˇ limiting the maximum permissible deviation to ą 5 % of the specified line width.
The small deviation from the standardised line widths is sufficient to deal with any variations within the limits of the printing procedures and does not pose unrealistic printing requirements. The permissible variation should not be used to vary the line strength randomly when drawing the map.

4.2 Introduction of 4-colour printing
A side-effect of digital cartography is the possibility of generating colour separations in the three basic colours cyan, magenta and yellow as well as black directly from the data file. In addition to the classic offset process with at least five pure colours it is thus also possible to use 4-colour printing as an alternative for O-maps. This process has a particular significance to prepare colour print-outs using laser- and ink-jet printers. Unfortunately, it is hard to regulate the colour appearance with 4-colour printing and the edges of the lines tend to be blurred. Both effects reduce the legibility of the O-map. Despite this difficulty, 4-colour printing can be used under certain conditions. The ISOM 2000 makes the following recommendations:

  • ˇ Four colour printing should only be used for international competitions when line width, legibility and colour appearance in the map have the same quality as from offset spot colour printing with five pure colours
  • ˇ Colour copies are a good alternative for non Foot-O disciplines, when conditions change rapidly and the map has to be corrected at the last moment.
The specific requirements of 4-colour printing will also be the subject of a later article.

4.3 Other forms of orienteering
The ISOM 2000 for Foot-O are the basis of the drawing specifications for maps to be used in other forms of orienteering. Both established technical standards - such as line width and screen definitions - and the major symbols should be the same in the maps for all types of orienteering. Despite these common features, special rules for the generalisation and extra symbols and comments are needed for

  • ˇ Ski-O,
  • ˇ MBO,
  • ˇ Trail-O,
  • ˇ Park- and Town-O.
4.4 Improving the ISOM for Foot-O
In addition to the general changes in line width and screen specification, ISOM 2000 has further changes specifically for Foot-O:

4.4.1 New symbols
113 elongated knoll
A small obvious elongated knoll which cannot be drawn to scale with a contour line (length less than 12 m and width less than 4 m). The height of the knoll should be a minimum of 1 m from the surrounding ground. Knolls larger than this must be shown by contours. The symbol may not be drawn free-hand or such that two elongated knoll symbols overlap. The symbol may not touch a contour line.

420 Special vegetation features (green point)
Symbol 420 can be used for special small vegetation features. The definition of the symbol must be given in the map legend.

4.4.2 Deleted symbols
Two of the symbols defined in ISOM1990 are a combination of other symbols. A specific definition of these symbols is thus not required, both are deleted:
515 wide ride,
532 Sports track.

4.4.3 Symbols moved to a new section
Some symbols could not be clearly assigned to one of the five groups used up to now (e.g. land forms, rocks and boulders, etc.). A new group "technical symbols" has thus been introduced. It contains the following symbols, which up to now had either been described in text form or elsewhere:
601 Magnetic north line,
602 Registration marks,
603 Spot height (previously 118).

4.4.4 Scales for Foot-O
The most suitable scale for Foot-O has been the subject of intense discussion in the last years. Questioning a large number of international male and female elite runners led to a clear vote, which was presented to the Mapping Conference in Årendal during the course of the 1997 World Championship. The Map Committee has accepted this recommendation and made a clear statement in the ISOM 2000 about the scale to be used for Foot-O maps:

  • ˇ 1:15,000 is the normal scale for Foot-O maps
  • ˇ Enlargements at scale 1:10,000 may be used for:
  • - relay,
  • - short distance,
  • - older and younger age groups.
  • ˇ Larger scales may be used for educational purposes.
Maps at scale 1:10,000 are enlargements of maps at scale 1:15,000. This means:
  • ˇ same number of objects (no more),
  • ˇ same level of generalisation,
  • ˇ screens retain the specifications for the 1:15,000 scale.
Terrain which cannot be legibly represented at 1:15,000 is not suitable for international orienteering.
A competition map should not be larger than A 3.
The reasons for the decision only to permit scale 1:15,000 in junior and elite competitions over the classic distance are the following disadvantages of maps at 1:10,000:
  • ˇ Route choice problem.
    Remote alternative routes are not recognised with a long leg between two controls
  • ˇ Long leg overview problem.
    For long legs over 2 km it is hardly possible to keep an overview of more than 25 cm on the map while running.
  • ˇ Map size problem.
    Elite routes up to 20 km long require very large map formats, which can hardly be handled in the competition.
  • ˇ Number of controls problem.
    The general experience is that a course on a 1:10,000 map has significantly more controls than a course of the same length on the same map at 1:15,000. The course is thus more a long "Short distance" event and route choice as an orienteering technique is often neglected.
  • ˇ Wildlife protection problem.
    With a reasonable map size of up to A3 it is only possible to represent an area of 3.0 km x 4.2 km, i.e. about 12 km2 at a maximum. Such an area is generally too small to be able to permit designation of adequate wildlife protection areas.

4.4.5 Adjustment of runnability
Many of the suggestions received were to do with the definition and representation of runnability. There was particular criticism of the representation of undergrowth and the classification of runnability. In addition, a new symbol for "vegetation barrier" was requested.
Unfortunately, no better alternatives were proposed for symbols 407 and 409 (undergrowth: slow running and difficult to run) so they were not changed. A new signature for vegetation barrier was not introduced. Instead, the definitions of the existing symbols were changed, as follows:

406: Forest: slow running
407: Undergrowth: slow running
The ratio for the reduced running speed was changed from 50 - 80 % to 60 - 80 %.

408: Forest: difficult to run
409: Undergrowth: difficult to run
The ratio for the reduced running speed was changed from 10 - 50 % to 20 - 60 %.

410: Vegetation: very difficult to run, impassable
The ratio for the reduced running speed was changed from 0 - 10 % to 0 - 20 %.

4.4.6 Change of screens
The following screens were newly defined:

310: Marsh
311: Indistinct marsh
The line widths were changed from 0.125 mm to 0.1 mm and the distance between the lines reduced from 0.25 mm to 0.2 mm. Small marshes and the shape of larger marshes can thus be better represented.

402: Open land with scattered trees
The screen specifications in ISOM 1990 were contradictory. Instead of 50 % of the area the yellow part was only about 35 %. By fixing 50 lines/cm and a point size of 0.4 mm the desired yellow part of 50 % is reached. The area on the map must be at least 10 mm2 large.

404: Rough open land with scattered trees
The screen specification in the ISOM 1990 definition could only be recognised with difficulty. The legibility is increased by increasing the yellow part from 50 % to 70 % and increasing the white dots from 0.4 mm to 0.55 mm. The area on the map must be at least 16 mm2 large.

406: Forest: slow running
408: Forest: difficult to run
To improve legibility the green screen is increased from 20 % to 30 % and from 50 % to 60%.

4.4.7 Enlargement of symbols
In areas with large granite rocks and boulders it was thought necessary to permit the enlargement of the standard symbols so as to represent significant differences in the sizes of individual rocks and boulders in boulder fields. In these special cases the following enlargements are permitted in addition to the normal symbols:
206: boulder (+20 %),
208: boulder field (+20 %),
209: boulder cluster (+25 %)

4.4.8 Open questions?
It can already be seen that the rapid development of reproduction- and print-techniques and the increasing standardisation in the newer orienteering disciplines will soon require revision of the corresponding sections of ISOM 2000. Further developments will be followed with interest.

Despite the very intensive discussions there are still some detail questions which have not been answered. These will have to wait for the next revision, ISOM 2010 (?). Until then, I would like to leave all those interested with the following open questions for systematic study and debate in the long evenings:

  • ˇ should the line ends for small rock faces be drawn square or rounded?
  • ˇ should the tags on small and large cliffs be drawn at the very end of the main line, or may the main line extend beyond the final tag?
  • ˇ how should a pit (116) be drawn?
  • - rounded lines at the upper ends and base of the "V"?
  • - rounded lines at the upper ends and a point at the base of the "V"?
  • - all line ends pointed? - at what angle ...?
Have fun with the discussions!

The ISOM 2000 can be found in Internet