Hello Nick, thanks for the link. Missed that one in my searching for RFID.
My project is very similar but more controlled as we are dealing with young people walking 80km around the general area of our school. More controlled because they walk a set route and we have marshalls and 'stop' points all along. We can get up to 2000 entrants of which maybe 200 will complete the walk - usually late at night walking in pitch dark through the cane areas but along paths, of course.
Cost is a factor for us as it already costs a whack to stage the event and our parent body have not been too forthcoming ito providing accurate technology so we can 'track' where their offspring actually are. We usually rely on marshalls writing down bib numbers at each stop and telephoning them to 'ground control' back at the school - it is here where things go awry as, the longer the day draws on, the less accurate it all becomes
Of course the cell phone towers usually go down on the day of the event as well! This means we cannot rely on telephony to record the walkers. BTW, it is not a race and timing is not individually done but by batch - usually the amount on one sheet of paper.
What all this typing means is that I am trying to impress on the organisers that we CAN collect accurate data and at a reasonable cost. Next time we will hit them for radio