  We introduce an innovative three-dimensional spectral approach (three band
parameter space with polyhedrons) that can be used for both qualitative and
quantitative analyses improving the characterization of surface heterogeneity
of (4) Vesta. It is an advanced and more robust methodology compared to the
standard two-dimensional spectral approach (two band parameter space). The Dawn
Framing Camera (FC) color data obtained during High Altitude Mapping Orbit
(resolution ~ 60 m/pixel) is used. The main focus is on the
howardite-eucrite-diogenite (HED) lithologies containing carbonaceous
chondritic material, olivine, and impact-melt. The archived spectra of HEDs and
their mixtures, from RELAB, HOSERLab and USGS databases as well as our
laboratory-measured spectra are used for this study. Three-dimensional convex
polyhedrons are defined using computed band parameter values of laboratory
spectra. Polyhedrons based on the parameters of Band Tilt
(R0.92{\mu}m/R0.96{\mu}m), Mid Ratio
((R0.75{\mu}m/R0.83{\mu}m)/(R0.83{\mu}m/R0.92{\mu}m)) and reflectance at 0.55
{\mu}m (R0.55{\mu}m) are chosen for the present analysis. An algorithm in IDL
programming language is employed to assign FC data points to the respective
polyhedrons. The Arruntia region in the northern hemisphere of Vesta is
selected for a case study because of its geological and mineralogical
importance. We observe that this region is eucrite-dominated howarditic in
composition. The extent of olivine-rich exposures within an area of 2.5 crater
radii is ~ 12% larger than the previous finding (Thangjam et al., 2014).
Lithologies of nearly pure CM2-chondrite, olivine, glass, and diogenite are not
found in this region. Our spectral approach can be extended to the entire
Vestan surface to study the heterogeneous surface composition and its geology.
