International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004
The KVR1000 photo with an effective pixel size of 2.2m (table
1) has some advantages for mapping against the multispectral
IKONOS image. As a typical analogue photo it is still
influenced by the film grain, but nearly all individual buildings
can be identified. Of course there is no discussion, the
a required pixel size of 2m for a map scale 1:50000. The rule of
5 pixels is not a fixed value; it is quite depending upon the
contrast and colour information. For the interpretation this size
may be required, but if we do have additional information like
the location of an object on the road, by the size we may get the
J M T
IKONOS pansharpened 1m pixel size
IKONOS pan reduced to 4m pixel size
E p.
a e
Figure 4: comparison of different IKONOS image products in the area of Zonguldak
panchromatic IKONOS image with 1m pixel size is quite better.
The range of grey values shows also details in areas where we
do not have a differentiation in the KVR1000 (see top of
building in lower right corner of figure 3) and it shows quite
more details (see the cars on the parking place in figure 3, lower
centre). Of course the advantage of the colour can be combined
with the high resolution of the panchromatic image by a
pansharpening (figure 4). This still improves the interpretation.
4. VISIBLE OBJECTS
The smallest individual object which can be shown in a map has
a size of 0.2mm caused by the printing technology but also the
resolution of the human eye in a usual reading distance. For the
identification of individual objects approximately 5 pixels are
required under usual conditions. If individual objects shall be
shown in a map, under this condition a pixel size of 0.2mm/5 =
0.04mm is required in the map scale. This would correspond to
information of the object (see figure 5). In addition in such a
topographic map only under special conditions individual
objects are presented. A topographic map in this scale range
includes more vector elements like roads, railway lines and
water courses. Vector elements can be identified with a much
smaller width. In the extreme case the separation lines on roads
can be seen even if they do have only a width of 0.2 pixels
(figure 6). The required pixel size for mapping is also
depending upon the contrast, spectral range and colour
information, so in general the situation is quite more complex
than just expressed by the pixel size in relation to the map scale.
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