An approach to the study of urban degradation through remote sensing: a case study of the eastern sector of metropolitan manila
May Celine T. M. Vicente
Manila Observatory and Lates-Cems, Ehess, Paris
Tel: 00 632 426 59 59; Fax : 00 632 426 61 41;
E-mail: celine@pusit.admu.edu.ph
A. Problem
In the Philippines, it is becoming evident that marginalization, environmental degradation and susceptibility to disasters are issues that need to be addressed immediately. There are also serious conflicts of spatial interests and disparate development priorities among concerned sectors. Then, too, there is the inability to localize these and other related problems in the appropriate scales of observation. Neither is there an adequate facility to study and monitor intersectoral development impacts. The above conditions are some principal reasons for the discrepancy between visions and actual evolution of development. For the most part, physical framework development plans are unrealized, as is the case in Metro manila. Urban planning in Southeast Asia, particularly in underdeveloped nations, is generally plagued by this discrepancy between perspectives and the actual pattern of development. This clearly shows ecosystems in diverse milieus (urban, rural, rurban, regional); that is, if sustainable development
1 is to succeed systematically and progressively. In particular, there is a need to integrate pre-disaster science into the socio-environmental planning process. Pre-disaster science includes such focal research areas as the upper atmosphere (e.g. ozone depletion), climate change (e.g. sea level rise), crustal deformation (e.g. earthquakes) and the environment (e.g. unclean water) (Communication by Fr. McNAMARA, SJ, Director, Manila Observatory).
This approach can be facilitated through symptomatic observations of socio-environmental health of the different ecosystems constituting the milieus. Research and analyses of the complex interactions between the elements: earth, air or wind, water and fire or energy and how these affect human settlements and animal habitats must be undertaken accordingly . This study addresses theoretical and technical issues of the aforementioned observations and approaches, in part, by applying remote sensing techniques in the survey and morphological analysis of urban blight. Urban socio-environmental planning is improved by the integration of this study in a model and wider framework of GIS that consequently facilitates the generation of strategic frameworks as "space plans".
The study area is the eastern sector of Metropolitan Manila in the Philippines. For the remote sensing analysis or urban degradation, SPOT multispectral and panchromatic data are used in a process of semi-automated interpretation. Image segmentation uses the spatial reasoning "disjunction-conjunction". Results of the study imply a possible cause-effect relationship between natural and man-made degradation in the area. They indicate, most of all, the usefulness of spatial analysis; image segmentation being the sole method for isolating and associating phenomenon. One can thus propose an assessment of critical urban environments. This is an aspect of pre-disaster science that must be incorporated into the (urban) socio-environmental planning process, particularly as this approach addresses the need for sustainable development of ecosystems.
B. The Approach or Methodology Adopted
We orient the research towards the extraction of themes by the segmentation of imageries. In accordance with the chosen orientation, one adopts an approach that is referred to as "disjunctive-conjunctive". When one speaks of this approach, one uses its context in the domain of logic referring to two forms of opposed but complementary reasoning.
(1) "Disjunctive" reasoning
A reasoning is considered "disjunctive" when it goes from the general to particular. In terms of spatial reasoning, the "disjunctive" step leads to the simplification of large thematic groups into their components. "Disjunction" is accomplished in the course of this research up to the level of perception of elements that we recognize to be objects. A major example of an ultimately "disjunctive" operator is the geometric intersection of pixels as represented by the minimum to maximum gray of objects corresponding, in turn, to various (classes of) indices or parameters (of detection).
(2) "Conjunctive" reasoning
In contrast, a "conjunctive" reasoning permits conclusions based on particular known facts. In this research, once the components of large thematic groups have been extracted, one adopts "conjunctive" reasoning by recombining groups of objects in a significant manner (communication by Mr. THOMOPOULOS, E.). The aim of this phase is to analyze relations between localized objects. One draws conclusions based on these large (recombine) thematic groups. As they have been defined in cartography, spatial relations between objects possess at times hierarchical, associative and ordinal (communication by mile RUAS, IGN) nature. These aspects prove to be very useful when one determines the type of processing that is appropriate in order to realize the "conjunctive" phase of the research. It is also essential to show that the two large families of degradation, that is natural and artificial, are not necessarily dissociated. This aspect justified, in part, the inferences in the "conjunctive" phase of the research. Within its limits, the step of "conjunction" is considered significant. The methodology adopted here applies the fundamental principle of conscientious, systematic and responsible planning as aided by RS-GIS. In terms of the detailed methodology for the application of RS-GIS, one refers to ""Figure 35, Tableau 6, Figures 36-40, Tableau 7 and Planches 12-14 (or Figures 52-54)" (VICENTE, 1998) that are to be presented in the Conference.
C. Results of RS-GIS Application
Thematically, we speak of the following:
(1) Degradation of the natural milieu
In total, we have:
-
12.59% of the study area, covered by water under the risk of
sedimentation or pollution.
- 12.33% of the study area in a state that is open to urbanization,
- 8.54% of the study area constituting flooded terrain,
- 1.54% of terrain favorable to urbanization, which may be flooded.
