Square Pole
A square pole is another name for a square rod or square perch, a traditional unit of area used in land measurement.
1 pole (rod) = 16.5 feet
1 square pole = 16.5 ft × 16.5 ft = 272.25 square feet ≈ 25.29 square meters
160 square poles = 1 acre
Square poles have historically been used in surveying and describing land parcels.
Circular Mil
A circular mil is a unit of area used mainly to measure the cross-sectional area of round wires and cables in electrical engineering.
Defined as the area of a circle with a diameter of 1 mil (1 mil = 0.001 inch).
Area = (diameter in mils)² circular mils.
1 circular mil ≈ 7.854 × 10⁻¹⁰ square meters or 0.7854 square mils.
Circular mils simplify calculations for round wires since area scales with the square of the diameter.