Construction of Vegetation Cover Map in Metro Manila for Urban Environmental Evaluation
Donkyu Yun, Akira Hoyano Tsuneo Matsunaga and Takao Katoh
Dept. of Environmental Science and Technology, Tokyo Institute of Technology
4259 Nagatsuta-chao, Midori-ku, Yokohama, 226-8502, Japan
Tel: (81)-45-924-5501 FAX: (81)-45-924-5553
E-mail : dyun@depe.titech.ac.jp
Introduction
To plan the comfortable urban, revegetation planning is a factor which cannot be overlooked. Especially, environmental alleviating effect of vegetation has been notifying on discussing the urban environment. First of all, the essential work on the vegetation planning and management is understanding the vegetation existing. In this study, it has been adapted an algorithm for extracting the VCRP (Vegetation Cover Ratio in a Pixel) from LANDSAT/TM and SPOT/HRV on Metro Manila. It has been also aimed to verify the value of VCRP and identify the appropriateness of the algorithm on tropical region using field survey.
Calculating the VCRP with the remote sensing data
Metro Manila (Philippine) is tropical region located in 14 degrees' north latitude. There are rainy (June to November) and dry season (December to may). The used data are LANDSAT/TM (observed in 1997.5.15) and SPOT/HRV (observed in 1997.5.2). The reference map was a digital map itemized into road., rail road, river and so on. Before calculating VCRP, it had been pretreated the rectification of the remote sensing data and the digital map with accuracy of 1.2 pixel.
It is necessary to find the mean MRVI values of vegetation and non-vegetation so as to calculate VCRP by adapting algorithm of VCRP estimation to Metro Manila area. The estimation method with MRVI histogram proposed by authors (l) has been adapted to find the mean MRVI values of vegetation and non-vegetation. Figure 1 shows an example of MRVI histogram extracted from LANDSAT/TM. The solid line represent calibration curves of part A and B, respectively, which curves are normal distribution curves. The mean values of the curves have the mean value of vegetation (A, 0.34) and non-vegetation (B, 0.19), respectively. The relation equation between MRVI and VCRP has been extracted using the mean values previously mentioned, and then VCRP of all site has been calculated. On the same way, VCRP has been also extracted using SPOT/HRV.
Verification of vegetation cover in representative blocks
(1) Methodology of Verification
The field survey as well as satellite observation has done the last period on dry season, so that can be considered vegetation growth state to be almost near. Generally, the pixel wise comparison is known as the verification method for vegetation cover in a block (VCRB). However this method has some problem such as rectification between the satellite images and ground-position. As an alternative method, it can be thought the comparison of each block. Since the method has the each integration value from several tens1 to hundreds1 pixels, there is little influence of rectification error. On the basis of above reason, we selected the block wise comparison method.
(2)Selecting the representative blocks
We selected the method for comprising the representative blocks, because surveying and comparing all blocks requires many times and great efforts, though it is desirable. Selecting the representatives blocks, it should be considered the vegetation pattern and the position identification. The blocks satisfied the above-mentioned two conditions were choose using the VCRP image, street map and field reaffirmation. Consequently, 14 blocks which contained no, low, middle and all vegetation cover blocks have been selected.
(3)Calculating the vegetation cover in a block from field survey
The measuring items for extracting vegetation cover in a block (VCRB) is as follows. The measuring method was done by taking a photograph, measuring with tape measure and with eye.
(a) Species and forms of trees: The dimension of tree forms (height, width, clear length) was measured in condition that the species of trees can be distinguished. In the other case, each tree height was classified into tall tree, middle tree and shrub.
