The marathon is a long-distance

Measuring marathon courses accurately Application by Pieter de Jager, Athletics South Africa Defining and measuring a marathon route is a complicated undertaking and it's vital to get it right. If a world record or world best performance has been set on the route, a re-measurement may be required and an independent route measurer must be able to follow the route according to the description and route map. The marathon is a long-distance running event with an official distance of 42,195 km (26 miles and 385 yards) that is usually run as a road race. The event was instituted in commemoration of the fabled run of the Greek soldier Pheidippides, a messenger from the Battle of Marathon (the namesake of the race) to Athens. The legend states that he was sent from the battlefield of Marathon to Athens to announce that the Persians had been defeated in the Battle of Marathon (in which he had just fought), which took place in August or September, 490 BC. It is said that he ran the entire distance of about 42 km without stopping and burst into the assembly, exclaiming "We have won" before collapsing and dying. When the idea of a modern Olympics became a reality at the end of the 19th century, the initiators and organisers were looking for a great popularising event, recalling the ancient glory of Greece. The idea of organising a marathon race came from Michel Bréal, who wanted the event to feature in the first modern Olympic Games in 1896 in Athens. This idea was heavily supported by Pierre de Coubertin, the founder of the modern Olympics, as well as the Greeks. The winner of the first Olympic Marathon, on 10 April 1896 (a male-only race), was Spiridon "Spiros" Louis, a Greek water-carrier. He won at the Olympics in 2 hours 58 minutes and 50 seconds. The women's marathon was introduced at the 1984 Summer Olympics (Los Angeles, USA) and was won by Joan Benoit of the United States with a time of 2 hours 24 minutes and 52 seconds. The marathon was one of the original modern Olympic events in 1896, though the distance did not become Year Distance (km) Distance (miles) 1896 40 24,85 1900 40,26 25,02 1904 40 24,85 1906 41,86 26,01 1908 42,195 26,22 1912 40,2 24,98 1920 42,75 26,56 1924 onwards 42,195 26,22 Table 1: Olympic marathon distances. standardised until 1921, since the only important factor was that all athletes competed on the same course. The marathon races in the first few Olympic Games were approximately 40 km (25 miles), roughly the distance from Marathon to Athens. The exact length of the Olympic marathon varied depending on the route established for each venue. The marathon distance The standard distance for the marathon race was set by the International Amateur Athletic Federation (IAAF) in May 1921 at a distance of 42,195 km (26 miles 385 yards). Rule 240 of their competition rules specifies the metric version of this distance. This seemingly arbitrary distance was that adopted for the marathon at the 1908 Summer Olympics in London. It is very interesting to note that the 42,195 km (metric distance) and 26 miles 385 yards (imperial distance) are identical to within 1,2 cm. For a marathon course to be certified by the IAAF the length must not be less than 42,195 km and the uncertainty in the measurement shall not exceed 42 m (i.e. 0,1 % of the total distance). To ensure that the total distance is not short, a Short Course Prevention Factor (SCPF) is applied to the distance. This factor is calculated as 0,1% of the total distance, which means that all IAAF-certified courses are intentionally lengthened by at least one metre per kilometre. The marathon (or road race) route The road is the route to be taken by participants in the event. Defining the course is the most important step in measuring a road because the measurement is irrelevant if participants in the event follow a different route. Before you can measure something, you must know what to measure. The race organiser will probably have a rough route in mind. First of all make sure that this route has been agreed with the local authority and the metro police. The race organiser, the Metro Police and the local authorities must also decide what part of which streets will be available to the runners. Will they be able to use the entire road, from curb to curb? Will they be kept to the right or left hand side? Are there any places where the course crosses a grass or gravel area? You must know the answers to such questions before you start to measure. PositionIT June 2012 65

Fig. 1: The blue line entering the stadium of the marathon route of the 2008 Beijing Olympic Games. Fig. 2: Athletes following the blue line. If runners are expected to stay to one side of the road this may cause uncertainty in measuring at corners. The precise route around each restricted corner must be defined prior to the measurement and set up in exactly the same way on race day. The easiest way to define a course is to say that the runners will have full use of the entire road, from curb to curb, or from curb to solid central divider, if one exists. This leaves no doubt where the measurer should measure. On race day the race director may put up barriers for safety purposes but, even if these intrude into the roadway, they will only lengthen the course slightly. If a course is laid out with many restrictions and barriers, it may measure short if the race organiser omits or misplaces the barriers. If a best performance is involved on a short course, it can be extremely embarrassing to the race organiser and to the measurer. It is therefore better to encourage the race organisers to keep the course to a simple design. Once the route is determined the measurement must be done along the shortest possible line without leaving the tarred road. Recently all Olympic marathons and several other major road races are marked by a painted line in a distinctive colour on the tar. Blue paint is used in most cases and those of you, who followed the last few Olympic marathons on television, would have noticed the blue line. This line is painted on the shortest possible route and any runner deviating from this line will run a longer distance than a runner who is following the line. For the Comrades, a race over 90 km, it is said that if you stay on one side of the road all the way between Durban and Pietermaritzburg, you will run up to 3 km further than the athlete who follows an imaginary blue line on the shortest possible route. Measurement tools A calibrated bicycle, fitted with a Jones Counter, is the only IAAF approved method of measuring road s. The Jones Counter, which is mounted to the hub of the bicycle s front wheel, is named after its inventor, Alan Jones, and the original manufacturer, his son Clain Jones. Between route measurers the instrument is still called a Clain Jones counter. The Jones Counter does not measure distance directly. It measures the revolutions and part-revolutions of the bicycle (front) wheel. Depending on the circumference of the bicycle wheel, one unit on the Jones Counter represents about 10 cm of measurement. It is of utmost importance to keep the circumference of the bicycle wheel as constant as possible throughout the measurement procedure for accurate results. The basis of the method of measurement is to compare the number of revolutions of the bicycle wheel (recorded in "counts") needed to cover the with the number of revolutions needed to cover a standard "" of known length. The method is simple and direct, but there are several important details to follow in order to obtain an acceptable measurement. The following eight steps are necessary to ensure an accurate measurement of a road race course: Define the road Select and measure a calibration course Calibrate the bicycle on the Measure the road Re-calibrate the bicycle on the Calculate the length of the road Make final adjustments to the road Document the measurement Each of these steps is of utmost importance, and none of them are to be skipped for accurate results. Define the road The planning procedures for a road have been mentioned previously and some of the most important elements to remember are: Make sure that you know what to measure Obtain approval from the local authority and Metro Police Decide on the coning and/or fencing of corners 66 PositionIT June 2012

Fig. 3: The Jones Counter. Fig. 4: Fitting the Jones Counter to the front wheel of the bicycle. Try to make use of the entire width of the road Keep the course as simple as possible Select and measure a calibration course A is an accurately measured base line used to calibrate the bicycle. It must be straight, paved, level and on a lightly travelled section of the road, free of parked vehicles. It should be at least 300 m in length, although a length of 500 m is recommended. A shorter calibration course near to, or on, race route is better than a longer one some distance away from the route. The effectiveness of the calibrated bicycle method of measurement depends on good calibration procedures, which demands easy and quick access from the to the and vice-versa. Calibrations are best used when "fresh", before conditions can change much. Calibration courses are often measured along the edge of a straight road, the same distance from the kerb as you would ride the bicycle when measuring. Avoid streets where vehicles are normally parked or measure far enough from the edge to avoid them (2,5 m). Bicycle paths next to roads may provide suitable locations, but the surface of the should be similar to that of the road you are going to measure. The marks defining the endpoints of the must be in the roadway where the bicycle wheel can touch them, and not off to the side somewhere. In general the endpoints should be nails driven into the road and marked with a paint line. The will be most resistant to obliteration if both endpoints are permanent objects like middle of manhole covers, which will mean that the will be an odd distance such as 524,37 m, which is perfectly acceptable. However for easier calculations a course to a set rounded length, like 500,00 m, is mostly used. The standard method of measuring a is with a steel tape. Route measurers always try to use a tape, a minimum of 30 m in length, made by a well-known manufacturer of surveying and construction equipment, with the temperature and tension specifications printed on the blade of the tape. A spring balance for checking the tension of the tape, and a thermometer for checking temperature are recommended, but most of you will agree that with temperature and tension we are looking for millimetre accuracy and for measurement of road courses we are looking for centimetre accuracy. Therefore you will find that most route measurers simply ignore these factors and simply use a steel tape with care to obtain accurate results. For a 500 m in length, 10 sections with a 50 m tape will be measured. Masking tape on both sides of the tape will help to have accurate measurements. For non-surveyors, which is the case with most route measurers, the most important factor is to keep an accurate count of the sections, and to keep the measurements in a straight line. It is highly recommended to route measurers to measure the twice with the second measurement done independently in the reverse direction, using different intervals (i.e. 12 sections of 40 m plus one section of 20 m). The final result will be based on the average of both measurements. If there is a significantly difference between the two measurements, further measurements should be undertaken until reasonable agreement is reached. As surveyors you would think it would be much easier to set up an instrument and measure the distance by EDM, or even use your GPS for the measurement. As already mentioned, most route measurers are not qualified surveyors and most of them will not even know how to set up an instrument. If you as a surveyor are approached to measure a calibration course for a route measurer, please keep the following in consideration: The bicycle wheel will follow the surface of the tar, which is more PositionIT June 2012 67

Fig. 5: The Jones Counter fitted to a bicycle wheel. likely to be followed by a steel tape than the straight line measured by an EDM Slope distance needs to be measured No scale factor or sea level adjustments must be applied If the is not of an even slope, measurement by an EDM will not be accurate enough Calibrate the bicycle on the The intention behind calibrating the bicycle before the road measurement is to calculate the number of counts registered on the Jones counter for every kilometre to be measured. A working constant will be calculated. The most important factor here is to keep the circumference of the front wheel as constant as possible by: Checking the condition of the bicycle s tyres and keeping them firmly inflated Ensure that the tyres are at air temperature by riding up and down the street for several minutes Avoid riding through water as this will cool the tyre down, changing the circumference of the wheel Keep the same weight and equipment on the bicycle as will be used during the measurement procedure Stay in a sitting position on the bicycle Ride the bicycle over the calibration course in an as straight line as possible, non-stop between the two endpoints, recording the readings at both sides and calculate the difference. Make sure that the axle of the front wheel is positioned exactly over the endpoints of the. Repeat this procedure at least three times for four sets of readings, two sets in each direction. Compare the four sets of readings and if the number of counts on any ride is very different to the rest of the rides, discard that ride and undertake further additional rides until four reasonably consistent sets of readings are obtained. The inconsistent ride may have been caused by swerving to avoid a moving object (person, dog or vehicle) or not riding in a straight line. Calculate the average of the four (or more) differences and divide this average by the length of the calibration course in kilometres to obtain the number of counts per kilometre. To prevent the total course from being short, a Short Course Prevention Factor (SCPF) is applied to this factor. The SCPF is calculated as 0,1% (1 m per kilometre) and the course is lengthened by that amount. Applying the SCPF is intended to result in road s being at least the distance stated, within the limits of measurement precision. It will also mean that slight variations in the course layout on race day will not invalidate the measurement. Measure the road With the working constant from the pre-measurement calibration the measurement data for the actual route can be calculated. Depending on the layout of the route, either the start line or the finish line of the route will be fixed. To ensure the exact distance of the route (10 km, half marathon or marathon) one of the two will need to move and will be determined on completion of the measurement. The finish line of most road race routes is in a stadium and is at a fixed position, the start line will therefore be determined on completion of the measurement and the route will be measured in reverse. At the start of the measurement, record the reading on the Jones Counter, or by rotating the wheel, set it to a reading which will be convenient to use as a start reading (a round thousand). Then, using the working constant, calculate the readings at the various split points you wish to note along the route (i.e. every kilometre, the halfway mark of the marathon, or every 5 km). Ride the bicycle along the pre-determined course and stop at each pre-calculated split point. Make a tentative mark on the road, using paint or a waterproof crayon and record a short description with a reference to a nearby permanent landmark, such as a numbered lamp post (i.e. in Fox Street, 10 m east of lamp post 25). When you reach the end of your list of pre-calculated counts, you will have established a tentative. On completion of this measurement the bicycle must be re-calibrated to confirm the accuracy of the measurements. Re-calibrate the bicycle on the The aim in re-calibrating the bicycle after the measurement is to check whether there has been any change in the number of revolutions and part-revolutions of the bicycle wheel which correspond to the length of the during the measurement of the road. This is to be expected, mainly due to temperature variations. If the temperature has increased, the calibration constant will be smaller, resulting in a course measured too long. A slightly larger constant may result when the temperature has dropped, resulting in a course measured too short. Unexpected change could indicate that there is some other reason for the difference, such as a slow puncture of the tyre. If this occurs, fix the puncture, re-calibrate from start and re-do the measurement. It is best to do the post-measurement calibration as soon after the 68 PositionIT June 2012

Fig. 6: Example of a route map. measurement as possible, before there is time for conditions to change. For the post-measurement calibration the same procedure is followed as for the pre-calibration with the average of a minimum of four rides. If measurements are done over more than one day, each day s measurement must be preceded and followed by calibration rides. Frequent re-calibrations during measurements will protect your measurements for more accurate results. A smart route measurer will re-calibrate frequently you never know when a flat tyre is coming. Calculate the length of the road The average value of the pre-calibration working factor and the post-calibration factor is called the constant of the day and is used to calculate the length of the road. The total number of counts recorded in riding the shortest possible route between the start and the finish divided by the constant of the day gives the exact length of the route. Make final adjustments to the road After calculating the length of the course, using the constant of the day, final adjustments can be made by adding or subtracting some distance to make the road the desired length. Adjustments should be made to each and every kilometre mark on a proportional basis. If the adjustment is relatively small, a more practical method is normally used by applying the total adjustment to the first or last kilometre by moving the start line or the finish line. These adjustments are normally done by using a steel tape. Document the measurement No job is done until the paperwork is done, and the last but most important aspect of the measurement is to draw up a comprehensive set of documentation of the route. This includes both the calibration readings and calculations, the measurement calculations, a detailed description of each kilometre mark and a detailed map (sketch plan) of the route. This documentation, including the map, must be sufficient to allow the race director to prepare the route on race day, or for a complete stranger to accurately re-locate the route, even some years after the race and possible re-surfacing of the roads. If a world record or world best performance has been set on the route, a re-measurement may be required and an independent route measurer must be able to follow the route according to the description and route map. The map must clearly show the route, indicating all the streets it uses, including any annotations which are necessary to make the route completely clear and unambiguous (e.g. what part of each road is available to the runners). Good maps are usually not drawn to scale and portions may be enlarged or distorted to show particular detail. Locations of the start line, finish line and kilometre marks must be described using taped distances from nearby permanent landmarks. Acknowledgement This paper was presented at AfricaGEO 2011 and is republished here with permission. References [1] International Association of Athletics Federations, Competition Rules 2010-2011. [2] Association of International Marathons and Distance Races (AIMS), The Measurement of Road Race Courses, Second Edition, 2004 (Updated 2008). [3] Wikipedia Website, viewed April 2011 http://en.wikipedia.org/wiki Marathon. [4] Google Images Website, viewed April 2011. [5] woistdasmeer.over-blog.com/articlemy-version-of-the-semi-marathon-ofparis-68921150.html. [6] www.flickr.com/photos/ jmslownsteady/2767713374/in/ photostream. Contact Pieter de Jager, Athletics South Africa, Tel 083 442-4295, dejagerpc7@telkomsa.net PositionIT June 2012 69