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Comparison of Standard Deviations in overlap area of corrected images 2b and 2c
2b band1 2c bandl 2b band2 2c band2 2b band3 2c band3 2b band4 2c band4
Minefloor 3:7 3.5 2.9 2.7 2.4 1.9 4.6 4.5
Regen 1 5.0 4.7 3.6 3.7 3.4 3.3 7.7 7.1
Native 33 4.7 6.8 53 4.1 3.5 15.3 13.9
Regen 2 4.6 4.4 5.4 4.7 4.6 4.0 7.1 6.3
Area Summary (number of pixels
Frame 2b
Mine floor
Regeneration 1
Native vegetation
ion 2
Note that whereas the 2b and 2c means differ markedly before
correction (Table 2), they agree closely after the correction
procedure has been applied (Table 3). The values in the
overlapping areas in the raw data were band-dependant and also
varied with the nature of the materials. Differences were in the
order of 15-30% between the bright and dark sides of the
images. The correction produced coherence in the overlapping
areas of better that 196 within a very low standard deviation.
The reflectance of a range of invariant targets (compared with a
BaSO, Lambertian standard) using an Exotech field radiometer
(Table 1) were made during the acquisition of the DMSV
images. The mosaicked images were converted into reflectance
values to provide a comparable measure of the vegetation status
and the ability to compare between the two minesites over time.
Classification into vegetation associations was done on the
mosaicked images with reference to field data. Fourteen
different vegetation classes were established across the Andoom
minesite. Statistics derived from these classes were then
transferred to the adjacent Weipa minesite mosaic. Despite the
50% cloud cover, several days difference in acquisition and
References:
Frame 2c
5185 5168
1576 1491
6511 6370
1410 1380
differences in camera settings, the cloud-free areas of the Weipa
mosaic were satisfactorily classified using those classes.
Conclusion
A heuristic approach has been adopted for correcting shading
effects across DMSV images that involves correlation with a
near-simultaneously acquired Landsat TM image. With this
method 196 differently illuminated DMSV images, collected in
1994, have been mosaicked and classified. Research is
continuing to further refine the technique and to evaluate the
effects of different solar angles and problems associated with
the non-availability of near-simultaneously acquired TM data.
Some breakdown of this method was detected at boundaries of
areas with large brightness differences (e.g. between bare mine
floors and native vegetation), where a slight blurring trend can
be observed near the edges because of the large difference in
the spatial resolutions of the two datasets. A method for
reducing this effect is being analysed. However, the results are
satisfactory for the intended use in minesite rehabilitation
monitoring.
King, D. (1991) Determination and reduction of cover type differential illuminations with view angle in airborne multispectral video
imagery. Photogrammetric Engineering and Remote Sensing 57:1571-1577.
Pickup,G., Chewings, V.H. and Pearce, G. (1995) Procedures for correcting high resolution airborne video imagery. [International
Journal of Remote Sensing. Vol 16, No. 9, 1647-1662
Lyon, R.J.P., Honey, F.R. and Hick, P.T. Second Generation Airborne Digital Multispectral Video: Evaluation of a DMSV for
Environmental and Vegetation Assessment, Proceedings of the First International Airborne Remote Sensing Conference and
Exhibition. Vol 2, 105-116
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996