Updated: 1 December 2007

2.2.2 Roads Vs Linear Features Example 3

Location of Example: 152°52'19" East, 25°22'57" South
Distinctive Characteristics:
  • Drains/Canals can be differentiated from Roads as they do not provide connectivity to the existing road network.
  • In Figure: note that the upper part of the drain near the water source gives off a light blue signature, indicating presence of water. The drain terminates at the water tank which also shows the same water signature.
  • If the Drain/Canal is completely dry it will appear lighter, similar to the surrounding soil and vegetation. The the edges will often appear much lighter, due to the excavated soil from construction.
  • Drains generally start at a water source and can end at a Reservoir, Water Tank or Sea.
  • Drains follow the topography of the land whereas roads may traverse hills and valleys.
  • The use of multispectral imagery band combinations can aid in the interpretation and differentiation of water.
Regional Considerations:
Figure: Representation of Canals/Drains Vs Roads

Figure: Orthophotography 60cm RGB=123 Figure: SPOT 2.5m RGB=321

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