  We consider conductance mapping of systems based on the two-dimensional
electron gas with scanning gate microscopy using two and more tips of the
atomic force microscope. The paper contains results of numerical simulations
for a model tip potential with a proposal of a few procedures for extraction
and manipulation the ballistic transport properties. In particular, we
demonstrate that the multi-tip techniques can be used for readout of the Fermi
wavelength, detection of potential defects, filtering specific transverse
modes, tuning the system into resonant conditions under which a stable map of a
local density of states can be extracted from conductance maps using a third
tip.
