GIS for the Development of a
Cebu Geographic Planning Atlas Eng'r .Christine Delfin
-Homez 1. IntroductionPlanning Officer Geoplan Cebu Foundation Inc. Cebu City Today's challenge to both developed and developing countries is sustainable development Philippines for one. Which relies most on is natural resources, is not an exemption on this call. The Province of Cebu which is located in Central Philippines, is experiencing rapid development. Especially in areas near the growth centers and/or metropolitan cities due to the influx of many local and foreign investments. Cebu City and its surrounding areas is experiencing massive infrastructure development. The pressure on land and its resources has greatly increased in recent year. The massive rapid population growth on Cebu and on t urban growth center in particular has aggravated the pressure on land and its resources. Since land and resources is finite, it is apparent therefore that planning and management should take into account all aspects of the land and its resources and that development should be sustainable . The knowledge about the geographic distribution of resources ( both natural and socioeconomic) is as prerequisite for a sustainable economic development and management of natural resources . topographic and thematic maps have always been and always be, one of the main tools for spatial planning, may it be urban, land-use or regional planning. Geographic information systems (GIS ) has been successfully used by many user in different develop countries as a tool in planning, monitoring and implementing projects . A survey of the existing data condition in Cebu, be it spatial or non-spatial, revealed that these data re complied at different offices and agencies and as a result very difficult for the user to access these various data . there is a need then to compile these datasets for better access and easy updating. The technology of Geographic information system (GIS), was employed to produce this Atlas. Te compilation of colored maps of different topics was one of the outputs to give better visualization and impression of the spatial aspects and phenomena inherent in the area. The development of this Atlas was supported by the Department of Science and technology (DPST, Region 7) through s grant in Aid Program and carried out by Geoplan Cebu Foundation, Inc. 2 . Objects The main objective of the development of the Geographic Atlas of Cebu through the use of GIS is to develop a geographic database of Cebu to facilitate improved spatial planning and decision making with regards to sustainable economic development and natural resource management. The Atlas can be use by various users such as planners, decision-makers, investors engineers , researchers , high school and college student and other end-users for various purposes among which are planning, monitoring, site selection, feasibility studies, resources inventory and monitoring, forecasting and a educational material. The system developed for this Atlas allows the combination of existing data sets to generate other sets to generate other topics, and to quickly update existing information. 3. Methodology : since commencing the Atlas project in April 1, 1997, different biophysical, socio-economic and demographic data have been generated and put into the system. Different coverage's have been generated to describe better the features of the area. These include Region 7, Cebu Province, Metro Cebu and some selected city and Municipalities. The Atlas project were undertaken in 5 steps:
3.1 Data Collection The success of the project depends on the equality of the data inputs. Since the data used in GIS represent always a generalized and abstracted picture of the real world at some point in time, it is essential for a useful GIS to have the right place and at the right time. It was necessary therefore to evaluate which data would be relevant to achieve the objective and also which data would be available and accessible at acceptable quality . Since the acquisition of primary data was not possible due to financial constraints, Geoplan decided to used secondary data available locally. An evaluation criteria was then set forth in the data collection plan, as follows .
The official topographic map series which is widely used in the country is based on 50 years old aerial photographs (1947) as is available at full coverage only at a maximum scale of 1:50,000. larger scales, such as 1:25,000 or 1:5,000 are only available for a few square kilometers . However, since the scale 1:50,000 is also widely used for thematic map series, we decided to use his as our base map for the atlas , in order to have full coverage of the island of Cebu. Relevant data ( map and statistical data ) was then collected from the different sector departments and agencies and evaluated for their usefulness. After this, data input started 3.2 Data Input The analog spatial data ( such as geological map series, soil maps, etc .) had to be manually digitized using a digitizing tablet . for each theme approximately 27 sheets at scale 1:50,000 had to be digitized as either point, line or polygon information . For digitizing the 20-m contour lines of the entire island of Cebu over one year was consumed . ( the often quoted statement hat more than 80% of the time of a GIS project is consumed for data input cab certainly be confirmed ). Digitizing of spatial data was carried out with ILWIS 1.4, after which the data was exported ( in DXF format or BNA) to Arc/Info for further processing. Attribute or statistical data were taken form official record and entered through the keyboard into tables. Then the records were assigned individual record numbers (ID or object identifiers ) to allow linkage with spatial data in Arc/Info ( DBF format ). Some data had been entered directly into the Arc/Info databases. Digital attribute data which were obtained form outside sources also needed to be preprocessed to match them with our own database structures. 3.3 Data management All digitized spatial data were further processed in Arc/Info, where the topology was built-up. Topology defines the absolute location in a coordinates system and the neighborhood relations. All spatial data were registered in the same coordinate system (UTM), unlike in CAD system, where the locations are always relative, not absolute. There are three basic forms of spatial data processed: the points, lines, and polygons Points and lines are the basic structures, polygons are closed lines . Examples are: Point : Location of miner deposits , rain gauges , etc . Line : Rivers and streams, contour lines, road network Polygon : Mapping units like geology, soils, administrative units . Under this step, all points , lines and polygons received a unique code ( object identifier ). For instance, over 500 polygons ( mapping units ) of the geological map needed to be labeled individually. The mapping units of another, far more complicated map ( Land Management Units ), had to be code individually with 1983 labels. Through this coding, it was eventually possible to link the attribute ( or non-spatial ) data with the spatial data ( e.g. political boundaries such as municipalities ) . this combination of spatial with the non-spatial data is the distinguishing characteristics of geographic information system . For the Atlas production, who kinds of data were distinguished. These are the spatial base data and thematic data. The base data , once generated, served s basis for all other maps to ensure the spatial consistency of e maps. Base data were for instance .
In this way, over 45 themes were generated and organized as layers. In each layer spatial data are organized , according to their them. While in one layer contour information about river are stored ( as line ), in another layer contour information ( as line ) may be stored, and in a third layer land use information (polygons ) maybe available. All information layers are equal and to hierarchy exists. All layers are referenced through a common coordinate system . 3.4 Data Analysis and Generation of New Information with GIS New information were generated through spatial operations ( geometric, logical combination, buffers, etc.) or statistical analysis. 3.4.1 Natural Resources Data Analysis One example of f data analysis done was through digital overlay and intersection of administrative, boundaries with the soil erosion map to calculate eroded arras for each of the 53 municipalities and cities of the island province. The contour lines were also used to generate a slope map, which could be overlaid with the administrative boundaries. Hence, it was possible to quantify areas above 18% slope inclination should be taken out agricultural or other use and made available for reforestation according to law ). Interpolated contour lines were also used ot generate a suede-three-dimensional model and to delineate automatically all major watersheds for the island. Hence, it was possible for the first time to calculate the areas of all major watersheds more all less accurately. Such area calculation can be done quickly with GIS, one the necessary database are already available, and can be used as decision-support for spatial planning purpose 3.4.2 Socio economics Data Analysis Through the combination of socio-economics and spatial data, new information could be generated. In the simplest case for instance, the population density ( populated per square kilometer ) for all 53 administrative units of the island. Some of the socio -economics data were available as a time series ( multi-temporal ). Hence the population change for instance between 1980 and 1995 could be mapped out. This is another advantage of digital GIS, because dynamic mapping becomes possible. Such information is very ;imp90tant for sustainable planning and can be presented in form of thematic maps. If one knows the age structure and the spatial distribution of particular age classes, forecast about the future needs for educational a institutions cab be made as well as for the optimum location . The examples for the potential fields of applications of e planning atlas are virtually limited . At present, the databank of the planning Atlas contains approximately 20 categories with over 50 individual layers , which are continually extended and upgraded. 3.5 Data Presentation the most important communication and visualization tool of the planner is the map. Each map represents in visual form spatial information. Some spatial patterns or phenomena only become visible, once they are color-coded and plotted on a map. The map output id the final product, which the planner eventually hands over to the decision-makers. All maps are displayed according to cartographic conventions, including map title, scale, scale bar, geographic coordinates, north arrow and legend . in all maps, the individual data sources or references are listed to gave due recognition and for further reference. In cases that data were interpolated or calculated form secondary data, such calculations were indicated in the legend of e map. Wherever geographic data was available, it has been indicated in the legend, and the respective are in the map has been colored. 4.0 Problem The problem encountered in the process of making the Atlas, are mainly related to :
Since the purpose of the project is just a compilation of all primary data on hand, different agencies were approached for their data. It was found out that some agencies, which make the same map, do not use the same classification. Other agencies do not also have the same classification used for a thematic map for different years. So comparison with available . 5.0 future Developments Since the compilation of secondary data needed for the Atlas depended on the willingness of many agencies and offices to cooperate, this Atlas is further far form being complete. Many other topics could have been n included, if relevant data had been accessible an available. The current limited Atlas version however is far from being comprehensive, complete and free of errors since Geoplan produced the Atlas based on existing data, which was collected and complied from official sources. However, suggestions and hints for correction are willingly accepted and will be incorporated in the updates that are going on. The data gaps that were established in the process of developing this Atlas then will serve as an eye opener to the concerned agencies to upgrade their data bank or for other sectors to research in the future. It is also that with the dissemination of the Atlas to many users, other regencies which were reluctant before to share their data for reasons of their own, will bow willingly share or make their data accessible. The current Atlas project serves as a catalyst for other provinces to produced their own Atlas . in fact the Department of Science and Technology (DOST) has already commissioned GEOPLAN to extend the coverage of the Atlas to e neighboring three provinces of Bohol, and Negros Oriental to eventually cover entire Region 7, considering that the Atlas was done in approximately 1.5 years of intensive work and still produced good results. The production of an initial hardcopy Atlas will serve as an initial step in developing a full electronic format in CD ROM and/or internet as the technology of DGI ( Distributed Geographic Information ) develop further. |