A longimeter is a transparent sheet of plastic with a regular grid of lines inclined at an angle of 
to the sides of the sheet. By counting the number of squares occupied by a linear
feature on a map (such as a river) for six different rotations of the sheet, the
length of the feature can be determined.
Longimeter
See also
Coastline ParadoxExplore with Wolfram|Alpha
References
Steinhaus, H. Mitteilungen der Sächsischen Akad. 82, 120-130, 1930.Steinhaus, H. Przeglad Geogr. 21, 1947.Steinhaus, H. Comptes Rendus Soc. des Sciences et des Lettres de Wrocław, Sér. B, 1949.Steinhaus, H. Mathematical Snapshots, 3rd ed. New York: Dover, pp. 105-110, 1999.Referenced on Wolfram|Alpha
LongimeterCite this as:
Weisstein, Eric W. "Longimeter." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Longimeter.html