Image Registration and
Mosaicking
The task of automated image registration can be divided into two major
components: 1) the extraction of features from images; and 2) the search
among the extracted features for the matching pairs that represent the same
object in the field of view of the images to be matched.
A new method was introduced for automated registration of DEM (Digital
Elevation Model) images with different noise levels
and amounts of missing data. With this new method, instead of using
isolated points of interest, edges in a generalized sense are first
extracted from the DEM images as the features on which the whole registration
process is based. The edges are extracted with multiple variance filters of
different widths followed by a linear feature extraction method based on
local maximum convolution. As the second step, the shape of the extracted
edges is represented with a rotation-invariant code that is generated
dynamically for each sub-section of an edge. Then the similarity of two edges,
one from each image, is evaluated with a parameter that reflects both the length of the edges and
the linear correlation coefficient calculated from their rotation-invariant
codes. When the matching edge pairs are determined, the corresponding pixels
within each edge pair are used as "tie points" to construct a redundant
equation set for a least squares solution for the projection parameters to merge
one DEM image into another, or one image of any type that is registered with
the first DEM into another that is registered with the second DEM. For this pair
of images, a total of 856 pixels from four matched
edge pairs served as "tie points" to form 1712 equations, from which
four projection parameters (one scaling, one rotation and two translations) were
obtained. The entire
process requires little human intervention.
As a quality check, after projecting one DEM into the other, the difference
between the two corresponding pixels was calculated, if there is no missing data
in either image.
Another example of a registered DEM pair and the
corresponding mosaic image of a radar image and a
digitized aerial photo are shown on separate pages.
Main Page ||
Original DEM Images ||
Extracted Features ||
DEM Mosaic I
DEM Mosaic II ||
Image Mosaic
