When you go on an orienteering course, you need to have some ways to measure things. Some of the methods used require you to have something of known length for comparison. A personal measurement log will help you with this.
Record some common measurements before you go out – arm span, arm reach, hand span, index finger length, foot length, wrist to elbow, and height. The important part is to be consistent in how you spread your hand or exactly where you measure. Then when you need to measure something on the course, you can choose the personal measurement which best fits your need.
You should also determine your pace length. Go to an large space of known distance. 100 meters is considered optimal. Measure the number of paces you need to walk that distance in a normal manner. Now divide the distance by the number of paces you took to cover it. That is your pace length.
Scouts BSA can use this with First Class Requirement 4a: Using a map and compass, complete an orienteering course that covers at least one mile and requires measuring the height and/ or width of designated items (tree, tower, canyon, ditch, etc.).