hatchet planimeter

geometry

enter image description here How does this instrument work? Here is a video that demonstrates its use.

After reading the wikipedia page, I still have no idea how it works. Any explanations that are easier to comprehend?


See Robert L. Foote: Geometry of the Prytz Planimeter. See also Mark Levi and Serge Tabachnikov On bicycle tire tracks geometry, hatchet planimeter, Menzin’s conjecture and oscillation of unicycle tracks, and Tom Apostol and M. Mnatsakanian: The method of sweeping tangents.

Related

How to determine in polynomial time if a number is a product of two consecutive primes?
Handshaking with no crossovers in minimum number of rounds: has this problem been studied?
Why the moduli space of complex structure in a compact complex manifold is of finite dimension
Show that $PSL(3,4)$ has no element of order $15$.
$\left(\frac{a^2+d^2}{a+d}\right)^3+\left(\frac{b^2+c^2}{b+c}\right)^3\geq\left(\frac{a+b}{2}\right)^3+\left(\frac{c+d}{2}\right)^3$
Why is this sum equal to the Logarithmic Integral?
Subtraction of elements in sets
Zombie Survival: What is the optimal way to place seven entities on an infinite grid to reduce number of adjacent pairs?
Does this "extension property" for polynomial rings satisfy a universal property?
Old French papers which haven't been translated into English
Krylov-Bogoliubov for measurable transformations
Rudin Theorem $1.11$