3.2. Land use/cover detection and analysis
To work out the land use/cover classification, supervised
classification method with maximum likelihood algorithm
was applied in the ERDAS Imagine 9.3 Software.
Maximum likelihood algorithm (MLC) is one of the most
popular supervised classification methods used with remote
sensing image data. This method is based on the probability
that a pixel belongs to a particular class. The basic theory
assumes that these probabilities are equal for all classes and
that the input bands have normal distributions. However, this
method needs long time of computation, relies heavily on a
normal distribution of the data in each input band and tends
to over-classify signatures with relatively large values in the
covariance matrix. The spectral distance method calculates
the spectral distance between the measurement vector for
the candidate pixel and the mean vector for each signature
and the equation for classifying by spectral distance is based
on the equation for Euclidean distance. It requires the least
computational time among other supervised methods,
however, the pixels that should not be unclassified become
classified, and it does not consider class variability. Ground
verification was done for doubtful areas. Based on the
ground truthing, the misclassified areas were corrected using
recode option in ERDAS Imagine. The error matrix and
Kappa Khat methods were used to assess the mapping
accuracy. Five land use/cover types are identified in the study
area viz., (i) vegetation (ii) agricultural land (iii) barren land
(iv) built-up land (v) water body.