  This paper aims to derive a map of relative planet occurrence rates that can
provide constraints on the overall distribution of terrestrial planets around
FGK stars. Based on the planet candidates in the Kepler DR25 data release, I
first generate a continuous density map of planet distribution using a Gaussian
kernel model and correct the geometric factor that the discovery space of a
transit event decreases along with the increase of planetary orbital distance.
Then I fit two exponential decay functions of detection efficiency along with
the increase of planetary orbital distance and the decrease of planetary
radius. Finally, the density map of planet distribution is compensated for the
fitted exponential decay functions of detection efficiency to obtain a relative
occurrence rate distribution of terrestrial planets. The result shows two
regions with planet abundance: one corresponds to planets with radii between
0.5 and 1.5 R_Earth within 0.2 AU, the other corresponds to planets with radii
between 1.5 and 3 R_Earth beyond 0.5 AU. It also confirms the features that may
be caused by atmospheric evaporation: there is a vacancy of planets of sizes
between 2.0 and 4.0 R_Earth inside of ~ 0.5 AU, and a valley with relatively
low occurrence rates between 0.2 and 0.5 AU for planets with radii between 1.5
and 3.0 R_Earth.
