botswana/namibia - Cour international de Justice

443. Both sensor systems are carried on board the LANDSAT series of satellites which are in
polar orbit around 700 kilometres above the earth's surface. The spatial resolution (pixel size)
on the newer LANDSAT TM SYSTEM is 30 metres (meaning that the smallest feature
resolved is at 30 metres x 30 metres square); it is particularly appropriate for depiction of
features on the Island since mapping scales can be rendered to 1:50,000 before blurring takes
place.
444. Satellite imagery of June 1975, March 1995, and June 1996 were subjected to analysis,
the results of which are set out in the Second Opinion. All three imageries indicate the greater
width and depth of the northern channel compared to the southern.
(i) LANDSAT MSS Imageries June 1975
445. Three bands are normally of interest when using LANDSAT MSS data: bands 4,5 and 7.
Bands 4 and 5 are two parts of the visible spectrum. MSS 4 is the reflective green
electromagnetic energy, while MSS 5 is reflective red of the chlorophyll absorption band
which is effective in depicting mainly darkened (i.e. non-actively growing) vegetation cover
(Ringrose et al, 1989). MSS 7 is the near infra-red band which includes the reflective peak for
green, actively growing, vegetation.
I. Classified image
446. Thus in the Classified image (Figure 15 copied and set out opposite page 99), the
contrast between swamp or floodplain vegetation and higher ground vegetation is brought out.
Open water mainly appears as blue. As far as channels are concerned, the firmer the blue the
deeper the channel. Thus it can be seen that while the northern channel in the vicinity of
Kasikili/Sedudu Island appears as a bold blue line, the trace is rather tenuous in the southern
channel which appears considerably smaller. The false composite can be similarly analysed.
II Single Band Image MSS 4
447. Again Figure 16, reproduced at para. 77 of Professor Sefe's Second Opinion, shows a
single band image using MSS 4. As band 4 has deep water penetration capabilities, channels
should appear in proportion to their relative size. Notice again on Figure 16 that the southern
channel of the Chobe River hardly appears in some sections, especially the meander loop and
the section immediately downstream of it. By contrast the northern channel is visible
throughout its course. This provides a further indication that the northern channel is the
deeper and wider of the two channels.
III Single Band Image MSS 7
448. As already stated, MSS 7 is the peak of the near infra red reflection and so is effective
depicting actively growing green vegetation. However, band 7 is also the trough for water
absorption and so water and wet soil appear as black. This band is ideal for showing landwater
contrast. Figure 17 reproduced at para. 79 of Professor Sefe's Second Opinion, shows a
single MSS 7 image. It can be seen that even on the floodplain and between channels there is
considerably dry land (the white patches). The southern channel of the Chobe River again
appears relatively small compared to the northern channel.
(ii) Thematic Mapper TM Imageries March 1995 and June 1996