  A 3-dimensional calculation of atmospheric neutrinos flux is presented, and
the results are compared with those of a 1-dimensional one. In this study,
interaction and propagation of particles is treated in a 3-dimensional way
including the curvature of charged particles due to the geomagnetic field,
which is assumed to be a dipole field. The purpose of this paper is limited to
the comparison of calculation schemes. The updated flux value with new
interaction model and primary flux model will be reported in a separate paper.
  Except for nearly horizontal directions, the flux is very similar to the
result of 1 dimensional calculations. However, for near-horizontal directions
an enhancement of the neutrino flux is seen even at energies as high as 1 GeV.
The production height of neutrinos is lower than the prediction by
1-dimensional calculation for near-horizontal directions, and is a little
higher for near-vertical directions. However, the difference is not evident
except for near-horizontal directions.
