Fishline length measurement device

A fishline length measurement device for a fishing reel having a spool rotatably mounted on a reel main body, comprising:

• spool rotation detecting means for detecting and counting a number of rotations of said spool;
• diameter measurement means for measuring a diameter of an outer circumferential surface of a fishline wound on said spool;
• first memory means for storing therein both a first linear equation and a second linear equation, said first linear equation relates both the number of rotations and the diameter of said outer circumference to a set of coefficients for each detected spool rotation, said second linear equation relates a length of the fishline fed from or wound onto said spool to both the number of rotations and said set of coefficients;
• first calculation means for calculating said set of coefficients for each detected spool rotation based on said first linear equation using both the number of rotations detected by said detecting means and the diameter of said outer circumferential surface measured by said measurement means, wherein a plurality of sets of coefficients corresponds to a plurality of detected spool rotations at which both the number of rotations are detected and the diameter is measured;
• second memory means for storing therein said set of coefficients for each detected spool rotation determined by said first linear equation;
• and
• second calculation means for calculating the length of the fishline fed from or wound onto said spool based on said second linear equation using both the number of rotations detected by said detecting means and said set of coefficients that correspond to the number of rotations.