  In this paper is discussed an application of signed measures (charges) to
description of segment and chord length distributions in nonconvex bodies. The
signed distribution may naturally appears due to definition via derivatives of
nonnegative autocorrelation function simply related with distances distribution
between pairs of points in the body. In the work is suggested constructive
geometrical interpretation of such derivatives and illustrated appearance of
"positive" and "negative" elements similar with usual Hanh-Jordan decomposition
in measure theory. The construction is also close related with applications of
Dirac method of chords.
