Trip report regarding remote sensing activities at ... - Up To - SOPAC

METHOD
1. Study of the existing documents
All mapping information relevant to the BA River area
was studied, especially the following :
_- the topographic map, Viti Levu, sheet 1 (1961),
_- the geologic map, Viti Levu, sheet 1 (1983).
_- the draft of the bathymetric map of the Sa River
Delta area (Ref. 2),
_ the positive film of the SPOT image
(1988),
-_ the paper print of the LANDSAT MSS image (1978).
For geographic incompatibility, the existing bathymetric
chart was not taken into account.
2. Processing the raw data (tape)
The satellite images are recorded on a Computer
Compatible Tape (CCT).
All processes used during the survey were obtained using the
SPT in-house image processing software named GRINGO.
The following method description takes the example of SPOT
data. Three channels are taken into account to load the
three SPOT channels :
-_ the infra-red band (XS3),
- the red band (XS2),
-_ the green band (XS1).
3. Decoding and extraction
Decoding the CCT is done in two stages, because the control monitor
can only manage a certain amount of data at a time. Therefore, we have
to select a restricted area. The control monitor used at SPT 1s a userprogrammable
image and graphic display; it is designed to off-load
display and interactive processing task from a central image
processing system. The maximum capability of the IVAS monitor is 1024 x
1024 pixels (elementary image unit). The size of the pixel is different
from one satellite to another. SPOT XS mode (colour) pixel size is 400
sq metres and LANDSAT MSS pixel size is 4800 sq metres.
In a first stage, the geometric coordinates of the selected
zone are calculated from the film or print of the image.
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