What is often of greater
concern, but much harder to quantify is the devastating effect salinity
has on the natural environment.
One of the most readily observable signatures of soil salinity is
the presence of dead trees. Whether it be through irrigation induced
salinity or sea water intrusion into coastal floodplains the effects
are similar.
Above: The death of large stands
of paperbark trees in the
Northern Territory is the result of salt-water intrusion into coastal
floodplains.
Using test sites in Northern Australia GecOz has developed
a sophisticated data fusion method to produce extremely accurate
maps of dead trees. Individual sensors are unable to isolate dead
trees, due to confusion with other cover types.
On a Landsat Image, for example, a stand of dead tree stumps with
no branches or leaves will be almost invisible from a vertical perspective.
The ground cover, which may be bare soil, will dominate the image.
Thus on a TM image dead trees are confused with bare ground.
In producing a SAR image, microwave energy is transmitted and received
at an angle. This means that objects that have a large vertical
face, such as tree stumps, are easily observable. However distinguishing
dead trees from live trees in SAR imagery is extremely difficult.
By locating areas which appear as bare ground on the TM imagery
AND as trees on the SAR imagery we are able to accurately map dead
trees.
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