Using ERDAS IMAGINE Suite of software
An assignment, about Image processing assessment .Using the ERDAS IMAGINE image processing system,to do a classifications of three provided images.
The aims of this assessment exercise are to confront you with the kind of problems commonly
addressed using remotely sensed data and, through the use of the ERDAS IMAGINE image
processing system, to familiarise you with some of the more important techniques available.
In broad outline, the exercise will require you to produce three scaled “maps” or images showing the
land use/cover in the Portsmouth area using two dates of Landsat and one of SPOT data.
You should also provide an account of the work carried out including details of any problems
encountered. N.B. You may find that you cannot achieve an answer that you would regard as
The final maps or images are not particularly important, it is the processes that you go
through and your understanding of the problems that are important.
To carry out this exercise you will have access to Landsat-TM data for June 1992 and December
2001 and a SPOT image from July 1987. Images covering the required area have already been
subset from the original computer tapes and are available on the image processing systems as:
A 1 :25,000 topographic map is also be available in the Map Library.
Stages in the Exercise
There are a number of stages that you will need to go through to complete the exercise successfully.
The details of how each stage is carried out are contained in the on-line Help. There are no printed
manuals for current version of Imagine (2011), but the on-line help files are very good.
You will only use a fairly small range of the options available in the Imagine suite but if you want to
explore its capabilities further on your own, you are welcome to do so.
1. Reading the images to the screen
The images for the two dates need to be examined by opening two viewers (see tutorials) and a
judgment of the differences based upon a purely visual inspection should be made.
The classification of the images will need to be carried out separately. You can adopt either a
”supervised” or “unsupervised” approach (see tutorials). Ideally, if you have time, you should attempt
supervised and unsupervised classifications of all three images. The classification schemes will need
to be the same for all dates to ensure maximum capability, even if the spectral parameters which
define each class do not match between the three dates (this will be a particular problem with the 2001
data). The output files will have to be given file names that allow you to identify them subsequently.
Normally this should relate in some way to the file name of the original data.
3. Geometric Image Correction
At this stage the three images will need to be brought to a common scale (derived from the 1 :25,000
map) in order that they can be merged to create the map of change. To do this points common to the
images and the map will need to be identified. Having identified the points the map coordinated will
need to be read for each point. To do this you will need to follow the instructions in the ERDAS
The determination of file coordinates is best carried out on the unclassified image although the
transformation will be applied to the classified image. You should obtain the coordinates of about 10
points in case some are found to be poor.
4. Comparing the results
Once you have completed the classifications and geocorrections, you will be ready to compare the
results. This can be carried out on-screen by opening up additional viewers or by producing a hardcopy
output of the classified images.
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