A Digital Image-based Elasto-Tomography (DIET) system for breast cancer screening has been proposed in
which the elastic properties of breast tissue are recovered by solving an inverse problem on the surface motion of
a breast under low frequency (50-100 Hz) mechanical actuation. The proposed means for capturing the surface
motion of the breast in 3D is to use a stroboscope to capture images from multiple digital cameras at preselected
phase angles. Photogrammetric techniques are then used to reconstruct matched point features in 3D.
Since human skin lacks high contrast visual features, it is necessary to introduce artificial fiducials which can
be easily extracted from digital images. The chosen fiducials are points in three different colours in differing
proportions randomly applied to the skin surface. A three-dimensional signature which is invariant to locally
Euclidean transformations between images is defined on the points of the lowest proportion colour. The approximate local Euclidean invariance between adjacent frames enables these points to be matched using this signature.
The remaining points are matched by interpolating the transformation of the matched points. This algorithm
has significant performance gains over conventional gradient-based tracking algorithms because it utilises the
intrinsic problem geometry.
Successful results are presented for simulated image sequences and for images of a mechanically actuated
viscoelastic gel phantom with tracking errors within 3 pixels. The errors in the phantom sequence correspond to
less than 0.3 mm error in space, which is more than sufficient accuracy for the DIET system.
Airflow over mountainous terrain can produce atmospheric waves in the lee of the mountains that have large vertical air velocities. These waves are used as sources of lift by sailplane pilots. Methods are developed for inverting flight data of airspeed and GPS-derived position to obtain estimates of the vector windspeed in mountain waves. Data from flight path segments with significantly different ground velocities within a region of constant windspeed give a well-determined solution for the windspeed. The methods are applied to flight data from a Perlan Project flight in lee waves of the Sierra Nevada Mountains in California.