How Are Open Water Swimming Courses Measured?

How Are Open Water Swimming Courses Measured?

Courtesy of WOWSA, Huntington Beach, California.

The swimmers at the Olympic marathon swim will be swimming along a course that is precisely 10,000 meters.

…but only if they are on the inside and swimming from buoy to buoy along the racing line.

Although the Olympic marathon swimming 10 km course set-up and logistics are a closely guarded secret, other major open water swimming events around the world use precise course measurement protocols. These races use some or all of the following procedures:

1. A CAD mapping system is used because it allows for the exact scale of the start pontoon and other objects (feeding pontoons, intermediate buoys) to be drawn.
2. The course (point-to-point or out-and-back), or one lap (in a loop course) is drawn taking into account any start offsets and finish chute straightaway.
3. The buoys are then drawn on within the racing line route and the GPS position is taken for each buoy.
4. This course is then reviewed with regards to the actual swim line used by the athletes.
5. Questions are asked to consider the dynamics of the competitors. For example, is there a long enough start straightaway before the first turn? Where will feeding pontoon be positioned and how far is it off the race line?
6. Questions are asked to consider the dynamics and positioning of the safety personnel and race officials? What is the safety cover? How will the safety personnel operate vis-a-vis the course shape and swimmers? Can all the boats be safely operated within the course and where are the evacuation points in case there are distressed swimmers requiring emergency action?
7. Questions are asked to consider the dynamics and desires of the media. For example, what television or photography angles are desired? That is, are there iconic images, landmarks, islands or perspectives that photographers or cameramen would like to shoot and can these images or landmarks be seen with the chosen course?
8. Questions are asked to consider the dynamics of the spectator experience. For example, is the course optimized from a spectator perspective or can the course be modified to direct the swimmers as close as possible to the spectators?
9. As a test, smaller marker buoys are temporarily posted in the GPS positions that are decided. Occasionally, there are obstacles that may not have been readily apparent (e.g., glare of sun, rock jetties, backwash from piers or breakwaters, large surf, shallow water, permanent mooring boats or boats that might not move for the event).
10. One intangible is the inherent feel for the course. Once the temporary course is set up, it is sometimes modified so the rhumb lines and overall course design is judged to be swimmer-friendly, media-friendly and spectator-friendly within the safety considerations.
11. Race organizers or their representatives (usually experienced open water swimmers) occasionally swim the proposed course to confirm all the previous course design decisions.
12. The course is then re-measured by driving around in the boat on the swimmers’ line with a GPS. The buoys are positioned within (on) the course (swim) line.
13. Coordinates are saved with distances between buoys laser measured.

Of course, a strong wind, heavy surf, poor anchors and/or whitecaps can result in a movement of the turn buoys and the course will be slightly off.

Copyright © 2012 by World Open Water Swimming Association
Steven Munatones