  By measuring angular-oscillation behavior of the heat capacity with respect
to the applied field direction, one can detect the details of the gap
structure. We introduce the Kramer-Pesch approximation (KPA) as a new method to
analyze the field-angle-dependent experiments quantitatively. We calculate the
zero energy density of states for various combinations of typical Fermi
surfaces and superconducting gaps. The KPA yields a merit that one can
quantitatively compare theoretical calculations with experimental results
without involving heavy numerical computations, even for complicated Fermi
surfaces. We show an inadequacy of the frequently-used Doppler-shift technique,
which is remedied by application of the KPA.
