True Scale at:
Parallel through center , between standard parallels
Azimuthal-like (book 7) Modified perpective view. True scale along straight central meridian, taped scale along Syene parallel (straight), and other lines concave and curved. Unused or lost.
PTOLEMY's PARALLELS ...
Each parallel is a circular arc of true scale. The scale is also true on the central meridian of the projection.
04%, so two lines about 1°37" east and west of it have true scale. The UTM grid was designed for large-scale topographic mapping in separate sheets, not for whole world maps. In particular, sheets from different zones don't juxtapose exactly.
After that, the two graphing papers are superimposed, providing a scale model of the landscape, or rather the targets in it. The true scale can be obtained by just measuring one distance both in the real terrain and in the graphical representation.
In conformal projections, large land masses are distorted while small shapes, local scales and relative angles in the large land mass are preserved. Equidistant maps show true scale between one or two points and every other point.
9996012717 (as opposed to the more normal scale of 0.9996 for the Transverse Mercator projection): this results in distances along the northing 180,000, almost exactly half way across Great Britain, being to true scale.
See also: Meridian, Map, Parallel, Projection, Map Projection