Graphics Programs Reference
In-Depth Information
imwrite(naivasha_rgb,'naivasha.tif','tif')
This command saves the RGB composite as a TIFF-fi le
naivasha.tif
(ca.
50 MB large) in the working directory that can be processed with other
software such as Adobe Photoshop.
8.5 Georeferencing Satellite Images
The processed ASTER image does not yet have a coordinate system. Hence,
the image needs to be tied to a geographical reference frame (
georeferenc-
ing
). The raw data can be loaded and transformed into a RGB composite
by typing
I1 = hdfread('naivasha.hdf','VNIR_Band3N','Fields','ImageData');
I2 = hdfread('naivasha.hdf','VNIR_Band2','Fields','ImageData');
I3 = hdfread('naivasha.hdf','VNIR_Band1','Fields','ImageData');
naivasha_rgb = cat(3,I1,I2,I3);
The HDF browser can be used
hdftool('naivasha.hdf')
to extract the geodetic coordinates of the four corners of the image. This
information is contained in the header of the HDF fi le. Having launched the
HDF tool, we activate File as HDF and select on the uppermost directory
naivasha.hdf
. This produces a long list of fi le attributes including
product-
metadata.0
, which includes the attribute
scenefourcorners
that contains the
following information:
upperleft = [-0.319922, 36.214332];
upperright = [-0.400443, 36.770406];
lowerleft = [-0.878267, 36.096003];
lowerright = [-0.958743, 36.652213];
These two-element vectors can be collected into one array
inputpoints
.
Subsequently, the left and right columns can be fl ipped in order to have
x
=
longitudes
and
y
=
latitudes
.
inputpoints(1,:) = upperleft;
inputpoints(2,:) = lowerleft;
inputpoints(3,:) = upperright;
inputpoints(4,:) = lowerright;
inputpoints = fliplr(inputpoints);
