Application of remote sensing for extraction of road
Information
Results and Discussions
Road Passing Through a Water Body
Clarity of a road depends on its background. Figure 1 shows a road (35m in width), passing
through a water body, contaminated with molasses, in different sensors. In ADEOS AVNIR
Panchromatic data, the background is very bright in the portion of the tank where water is dried
out and, however, road can be seen distinctly. On the other hand, the portion of the tank, where
contaminated water is available, appeared very dark and the road can also be seen clearly. In this
case, molasses absorbs most of the energy whereas reflectance from the road is very high and
thereby provides a very good contrast. In SPOT Panchromatic data, rainy season was just started
and probably, therefore, dried out portion of the tank is not as bright as in the case of ADEOS
data. This could not be confirmed due to unavailability of ground truth data at that instant of
time. In ADEOS Multispectral data, the tank was full of water, therefore, the road appeared very
bright against its background of dark contaminated water. LANDSAT TM data shows similar
behaviour with ADEOS AVNIR Panchromatic data as both the images were acquired nearly in
the same time of two different years. SPIN-2 data is not available for this area
| ADEOS Panchromatic |
SPOT Panchromatic
|
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| |
| ADEOS Multispectral |
LANDSAT TM |
 |
Figure 1 A Section of road passing through a water body
Road Passing Through a Paddy Field
A road passing through an area with uniformly distributed vegetation, like paddy field
becomes prominent due to their different reflection characteristics. A section of road with a
width of 35m (Figure 2), passing through a paddy field can be seen very distinctly in ADEOS
Panchromatic data. There is a very good background contrast throughout the road section and
edges of the road can be identified clearly. SPOT Panchromatic data also provide a clear picture
of the road. Due to the low resolution, in the case of ADEOS Multispectral data and LANDSAT
TM data, edges of the road section is not prominent, though the road can be clearly identified as
shown in the figure. SPIN-2 data is not available for this area.
| ADEOS Panchromatic |
SPOT Panchromatic |
 |
| |
| ADEOS Multispectral |
LANDSAT TM |
 |
Figure 2 A Section of road passing through a paddy field
Road Passing Through an Urban Area
Images in Figure 3 show a section of road through an urban area. Ground width of this
road section is 64m. Irrespective of spatial resolution, the section of road marked by a circle can
not be identified clearly in any of the images. However, in certain sections, where background is
not structural material, the road can be identified. Thus, if a road passes through such an urban
area which gives similar spectral signature as construction materials, it is very difficult to
identify the road. In such cases, there is a need to look for certain sections of the road with a
background other than man made materials, for identification.
| ADEOS Panchromatic |
SPOT Panchromatic |
 |
| |
| ADEOS Multispectral
| LANDSAT TM |
 |
Figure 3 A Section of road passing through an urban area
Locating Bridges on a Road
A bridge with two parallel roads of 10m width each, one for up coming and another for
down going vehicles, with a gap of 5m in between (25m in total) can be identified separately in
ADEOS Panchromatic and SPOT Panchromatic data. ADEOS Multispectral and in LANDSAT
TM data can not distinguish these two parallel roads separately. SPIN-2 data is not available for
the location of the bridge.
