With the rapid growth in population throughout the world, it is crucial to have a well-concerted plan for urban expansion. Satellite or Airborne images give Urban planners synoptic views of large areas which allow them to lay plans for urban expansion effectively. Using December, 1990 and February, 1997 SPOT Panchromatic and Multi-Spectral imagery of the Sydney Metropolitan area, the paper demonstrates how to use ER Mapper in processing those images for urban planning and to monitor changes that took place over the 1990-1997 years.
Introduction
The study area is the Sydney Metropolitan area. SPOT Imaging Services Pty Ltd's permission to use the December, 1990 and February, 1997 SPOT Panchromatic and Multi-Spectral data of the Sydney Metropolitan area is much appreciated and acknowledged. The location map (Fig. 1) shown below covers most of the study area which is approximately 38 sq kms. The paper discusses rectification of the images, standardizing the atmospheric condition of the 2 dates imagery, change detection between the 2 dates SPOT Panchromatic and Principle Component number 1 of the 2 dates SPOT Multi-spectral imagery. A few small areas are selected to show the effectiveness of the change detection techniques applied on the 10 and 20 meters resolution SPOT Panchromatic and Multi-Spectral images.
Figure 1. Location map of the study area (Sydney Metropolitan area)
Processing
Rectification:
The June 1998 Orthocorrected SPOT Panchromatic image was used as the master dataset to rectify the December 1990 and February 1997 SPOT RAW images. Average RMS error of less than 0.5 is achieved for all the images (SPOT Panchromatic a RMS of 0.454 for 12/90 and 0.374 for 2/97 and SPOT Multi-Spectral 0.347 for 12/90 and 0.248 for 2/97). The common area of the 2 dates imagery was then subsetted for the study. The study area covers, Sydney in the East, Parramatta in the West, Hornsby in the North and just above Cronulla in the South (Fig. 1).
Standardizing the atmospheric condition:
The atmospheric condition was most likely to be different at the time the 2 images were taken, one in December, 1990 and the other in the February, 1997. To do change detection it is necessary to standardize the atmospheric condition of the two-date imagery. Bi-variant scattergram was used to find out the cut-off values that might have contributed by the atmosphere. The cut-off values were then used to standardize the atmospheric condition of the two-date images.
Change detection:
The recently developed Local Council Applications Wizard (LCAW) (Fig. 2) was used to carry out change detection of the Sydney Metropolitan area using the two dates SPOT Panchromatic and Multi-Spectral data. Though LCAW was developed for Local Councils to process Airphotos and Scanned maps, both Airphoto Panchromatic and SPOT Panchromatic are one band data. Similarly, both RGB Airphotos and SPOT Multi-Spectral data are 3 bands imagery. Hence, Change Detection (2 dates Airphoto Pan & Pan) and Change Detection (2 dates RGB & RGB) modules were used to carry our change detection of the 2 dates SPOT Panchromatic and Multi-Spectral data. The processing time of the change detection between the 2 dates SPOT Panchromatic was about 2 minutes and for the Multi-Spectral was about 3 minutes. Processing time for 2 dates Multi-Spectral data took longer because it uses Principle Component number one of the 3 bands Multi-Spectral data which requires statistic calculation of the datasets. All the processing steps are in-built into the LCAW and hence is very fast to process data and leaves a lot of time for the author to analyze the processed images.
Figure 2. Local Council Applications Wizard main menu window.
