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International Institute for Geo-information Science and Earth observation (ITC) 2001

Building a soil information system for multi source data integration (A case study in Lake Naivasha area, Kenya)

BEZU TILAYE BITEW

Titre : Building a soil information system for multi source data integration (A case study in Lake Naivasha area, Kenya)

Auteur : BEZU TILAYE BITEW

Etablissement de soutenance : International Institute for Geo-information Science and Earth observation (ITC)

Grade : Master of Science in Geoinformation Science and Earth Observation 2001

Résumé
This study was aimed at the design of a Soil Geographic Database (SGDB), as part of a Soil Information System (SIS), for the improved management of soil and land resource data relevant to an area around Lake Naivasha in Kenya. Emphasis is given both to the rescue of existing data, available in different formats from a variety of sources, and to the improvement of user access to adequate soil information for multiple purposes. The methods adopted for SGDB data modelling and for SIS development are the relational data model and the iterative structured information system development method, respectively. Two components of the SIS were designed : a relational database structure having twelve relations, and a prototype information system architecture consisting of four subsystems. The analysis of users’ information requirements provides the input to the actual SGDB design process. The user need assessment showed that 94% of the respondents have indicated a clear need for soil information for their current and future resource management activities. A large majority (73%) of the users obtain their soil information by sending soil samples abroad for further analysis. Users have a clear preference for digital rather than analogue data format primarily because of the ease of handling and further analysis. This study proposes a working approach for multi-source data integration and standardisation in a common database structure. Correlation tables have been developed to handle the multi-category issues when dealing with different soil survey approaches and/or soil classification systems. A nested database design approach is applied to integrate data resulting from surveys at different levels of detail and map scale. The conversion of existing soil data from analogue to digital format involved a geometric correction process supported by additional ground control. For spatial data capture in the field two approaches have been followed. In those cases where not enough identifiable ground control points (GCP) could be selected on a geometrically-accurate base map, a directional compass traversing method was applied with distance measurement using a measuring tape and GPS readings. Whenever enough GCP could be identified, only GPS readings have been used. In both cases the spatial data have been successfully converted from analogue to digital format, using the same geometric definition. However, when the locational accuracy of the geometrically corrected soil maps is compared, the compass traversing approach provides better quality. Both metadata documentation and user interface design has been applied to improve user access to the organised soil data. The Content Standard for Digital Geospatial Metadata (CSDGM) as developed by the Federal Geographic Data Committee (FGDC) of the USA has been applied. The user interface design has been done using Ms Access navigation screens.

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