  We present the Agile REconstruction Method (AREM) for gamma-ray (30 MeV - 50
GeV) direction reconstruction applicable to high-resolution Silicon Tracker
detectors in space. It can be used in a "fast mode", independently of Kalman
filters techniques, or in an "optimized mode", including Kalman filter
algorithms for track identification. AREM correctly addresses three points of
the analysis which become relevant for off-axis incidence angles: (1) intrinsic
ambiguity in the identification of the 3-dimensional $e^+/e^-$ tracks; (2)
proper identification of the 3-dimensional pair production plane and
reconstructed direction; (3) careful choice of an energy weighting scheme for
the 3-dimensional tracks. We apply our method to simulated gamma-rays in the
AGILE detector. The excellent spatial resolution obtained by the AGILE Silicon
Tracker, providing crucial analog information, makes it possible to improve the
spatial resolution of previous detectors (e.g. EGRET) by a factor of ~ 2 in
containment radius at gamma energy ~ 400 MeV. In this paper we present the
results of our 3D-method for a selected sample of photon incidence angles and
energies. A more comprehensive and complete discussion including the use of
Kalman filter algorithms will be the subject of forthcoming papers.
