IEEE Geoscience and Remote Sensing Magazine - December 2020 - 32

random-access memory. Image Display software developed
by SAC (ISRO) is used for displaying the images.

all of the GCPs in the sensed image, and the sensed image
was registered with respect to the reference image.

RESULTS USING INSAT-3A CCD DATA
This section demonstrates the results of INSAT-3A CCD
data registration. A case for multitemporal image registration is shown in Figure 7 for a CCD image. Figure 7(a)
and (b) shows a synoptic view of a reference and a sensed
image, respectively, in the display panels. The sensed
image is to be registered with respect to the reference image. Nonlinear distortions and corresponding registrations at different points in the sensed image are shown in
Figure 8(a)-(c).
The left-hand panel of Figure 8(a) shows a distortion in
the sensed image at the current cursor position, with respect
to the same point in the reference image. As can be seen,
the sensed point 1 is shifted 31 scan lines down side and 08
pixels right side, with respect to reference point 1. After applying the registration algorithm, the geometrically shifted
sensed point 1, shown in the left-hand panel of Figure 8(a),
is aligned with respect to reference point 1, as shown in the
right-hand panel of Figure 8(a), i.e., scan: 2641, pixel: 3031.
The pixel brightness value of the sensed image is preserved
at registered point 1, i.e., 0048, referring to Figure 8(a).
Figure 8(b) and (c) demonstrates registration at two more
points. It should be noted that geometric distortions observed at Figure 8(b) and (c) are nonlinear when compared
to the point in Figure 8(a). Similar results were obtained for

REFERENCE BOUNDARIES GENERATION
FOR INSAT-3A CCD DATA
After an image is registered with a reference image, boundaries are then overlaid over the registered image. As the boundary for CCD images was not available, it has been generated
using the VHRR boundary image data from the same satellite, i.e., INSAT-3A. This section discusses the reference
boundaries' generation and shows the related results on the
INSAT-3A CCD data. VHRR reference boundaries (full globe
product) are generated from the shape file provided by the
IMD, New Delhi.
A 4,000 × 4,000 size image is first cut from the VHRR
full globe product, with the same view as that of the CCD
images. The cut image was treated as a sensed image for the
warping. The reference image is made of 8,000 × 8,500, by
padding zeros all around the image area. Points on the Indian coast and surrounding area were identified manually and
used the warp (6) with respect to the reference image 8,000
× 8,500 to generate the boundary image. Figure 9 shows a
synoptic view of the reference CCD image and its generated
boundary image.
The generated boundaries are then overlaid over the reference image. Figure 10 shows the CCD boundary overlaid
over the reference image, and Figure 11 shows two full-resolution snapshots of the boundaries fitting on the image.

3ACCD_29OCT2006_0701_03.rad

3ACCD_11FEB2007_0901_03.rad

(a)

(b)

FIGURE 7. The INSAT-3A CCD data registration. (a) The reference image and (b) the sensed image to be registered with (a).

IEEE GEOSCIENCE AND REMOTE SENSING MAGAZINE

DECEMBER 2020

IEEE Geoscience and Remote Sensing Magazine - December 2020

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