Ribbon and Footprint Codes on a Snowy Lakeshore Trail

The Snowy Lakeshore Trail Test

At a snowy lakeshore trail, a team needed to send short messages from a lookout to a supply station 15 meters away. The team tested two pattern systems. In the ribbon system, a sender held up two ribbons in order. Blue followed by white meant Bridge Ahead. White followed by blue meant Turn Back. Blue followed by blue meant Wait Here. White followed by white meant Help Needed.

The team also tested a footprint system. A long step followed by a short step meant Bridge Ahead. A short step followed by a long step meant Turn Back. Two long steps meant Wait Here. Two short steps meant Help Needed. The receiver had to read each pair from the sender's first mark to the second mark.

The sender sent each of the four messages three times with each system. The team kept the distance, sender, receiver, and message set the same. First, the air was clear. Then the team repeated the test while light snow was falling. The results were recorded as correct messages out of 12 and as the average time to send one message.

In clear air, the ribbon system produced 11 correct messages out of 12 and took 4 seconds per message. The footprint system produced 9 correct messages out of 12 and took 6 seconds per message. During falling snow, the ribbon system produced 7 correct messages out of 12 and took 5 seconds per message. The footprint system produced 10 correct messages out of 12 and took 7 seconds per message.

After the test, the team noticed that falling snow sometimes covered part of a ribbon. Snow also made a footprint pair take longer to make because the sender had to check each mark. The team treated these observations as possible explanations and planned more tests before making a final decision.