Central Africa Geographic Information System Objectives The explicit spatial nature and highly variable content, scale and projection of the different data sets that were collected for this project made it imperative that a flexible and powerful geographic information system environment be adopted for management and analysis. A major component of this project (in time and effort) was the structuring and development of a regional GIS for the countries included in the central African study area based on the identification, acquisition, documentation and co-registration of suitable data sets. The primary purposes of the GIS were:
Data were collected from a number of sources, at various resolutions, levels of completeness, and accuracy. Data sets came from other GIS, tabular data files, hard copy paper maps [those needing digitization], textual descriptions in research reports, raw digital satellite images, and classifications of digital satellite images. Integrating these data sets into a GIS was complicated by problems of database compatibility, geo-referencing, and attribute inconsistency. Acquisition was a long process that took us from identifying existing data and sources to contacts, agreement on data sharing, actual physical acquisition of data, data evaluation and QC, and eventually, entry of the data into our GIS in digital form. We selected the pseudo projection of latitude and longitude for use in the Central Africa GIS since latitude and longitude coordinates are by far the most commonly encountered in maps and other GIS datasets. It is straightforward [using GIS tools] to transform data in lat/long to other projections if needed. Although accuracy is sometimes an issue with projections when linear or areal measurements and comparisons are carried out, these were not an issue here because conversions can be easily carried out to the most appropriate projection and map units when such comparisons are required. We found that attribute data [the descriptions of the spatial data] were usually consistent within single data sets, but not from one data sets to another. In order to compare maps with differing attributes, one must first group attribute categories that are compatible to both datasets. This leads to very general categories such as forest, transition forest, grassland, and water. Data sets include, administrative limits, population, climate, hydrography, infrastructure, soils, vegetation maps, protected areas and remote sensing derived maps produced by this project. A summary of the main layers is presented in Table 1.
After putting together the GIS for this project, we can make a few observations and recommendations. Very few groups in Central Africa are well positioned for the technical effort required to manage and analyze a regional GIS database. We would recommended that a Central Africa GIS be continued at some centralised archival site (preferably within the region) where new data could be entered, analyses carried out to meet the needs of the user community, and new datasets be created for community use. Such a site could also respond to users' needs for new data, such as searching for additional existing datasets to add to the GIS, updating existing data sets such as rainfall to fill in gaps of missing information, addition of field notes and results from biodiversity and ecological studies, and addition of new data sets from results of remote sensing interpretation. These results could be made available to the research community through some kind of data sharing method on a network or through a metadata browse. The continuation of this work is logical given the time and effort already invested in GIS assembly and utilization. The data have served this project well, along with African collaborators and could easily be used by other projects with regional or global scope. The successful linkages that we have developed with other data-owning organizations and users would facilitate continuation of the GIS elements of this project. It is not feasible to recommend Unix-based workstations for GIS use in the most of the countries of central Africa at this time. A PC based GIS is more appropriate since PC's are already in use and are supported by a growing user community in the region. Workstations are much more expensive and complex, requiring much more systems level support both in hardware and software maintenance and in general system administration. In instances where the PC's can not handle a task, ties with outside institutions or a highly capable archival site would allow both analysis and data generation capabilities. Data sharing is the best way to reduce the costly data acquisition phase of projects. As a means of establishing a data sharing environment, ftp sites could be set up for data transfer and other media such as CD- ROM or a cross-platform tape media explored for use as a portable library or for data interchange. Methods should be investigated for effective communication with GIS installations on the continent of Africa. Expensive international phone communications and lack of continental networks in Africa hamper GIS expansion and the spread of knowledge both within the countries of Africa and with the rest of the world. Bulletin boards set up around use of telephone communication at off-peak hours could foster electronic contacts, information sharing, and problem solving. A key part of information sharing is the basic communication of what
data is available (Metadata). Before data is requested, an appropriate
description, or metadata listing, should be available for potential users
to decide if a particular data sets is really useful. Metadata standards
and initial listings could go a long way towards beginning a text-based
information sharing network.
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