Rod (measure of distance)

[civilwarbuglertn]

a unit of linear measure, 51/2 yards or 161/2 feet (5.029 m); linear perch or pole.

I kept running across this in letters and finally found out the correct distance.

[James George]

The reason why is a "Rod" is from the old English Measurement scale.

[larry_cockerham]

I believe the survey rod was actually carried in the field for measuring. That length was a practical consideration as it was about the limit for carrying or storing for transport. Chains, tapes etc. were yet to appear.