Monday, 10 July 2006

Making the Old New: Rescue, Reuse and Renewal of Legacy Soil Surveys.

David G. Rossiter, International Institute for Geo-Information Science and Earth Observation (ITC),, P.O. Box 6, Enschede, 7500 AA, Netherlands

The World is full of unused, even forgotten, soil geographic information in the form of soil surveys sitting forlornly on a library shelf, stored on obsolete magnetic tapes, turning to dust in a storage cabinet, or in the private collections of retired soil scientists. Disasters-- natural, man-made, and political--can destroy these forever. This is especially unfortunate in Less-Developed Countries (LDC), as it is both more likely that the data will be lost and more unlikely that a new survey can be commissioned. All environmental data is valuable and worthy of protection, but soils data maybe more than most, because of its high cost, the specialised training required of a good soil surveyor, and the small number of actual observations. Many soil surveys in LDC were quite good. Former colonies were surveyed by the colonial power; more recently, development projects have often included soil surveys. These surveys differed in their objectives, standards, and concepts, but all provide valuable information that was obtained at considerable cost. However, almost no soil geographic information on LDC is available in digital form; this situation has not appreciably changed in the past five years except for some compilations produced by international organizations, notably ISRIC and the FAO. The first step is simple data rescue: physically recover, protect and catalog the lost material. A natural second step is digitalization by scanning maps and reports; ISRIC has taken the lead here and much information from Asia and Africa has already been rescued. However to get full value we need to move beyond rescue to data renewal: bringing the legacy data up to modern standards by taking advantage of technological and conceptual advances in geoinformation technology.

The objectives of a data renewal exercise are:

  • to recover the investment in soil survey and use the survey as intended for land use planning, agricultural extension, etc.;
  • to prepare for supplementary or new surveys, e.g. design sampling plans on the basis of known strata and existing samples;
  • to provide a base line for longitudinal studies; and
  • to provide a layer for integrated environmental or planning GIS.

A renewed soil geographic database should include:

  • a GIS coverage (for maps): geo-referenced and geodetically-correct to some specified accuracy, commensurate with its scale;
  • structured attribute databases for both point observations and interpreted polygons;
  • a synoptic medium-resolution multi-spectral image (TM-type) as background;
  • a medium-resolution elevation model (DEM) and derived terrain parameters (slope gradient and aspect, curvatures, wetness index etc.) as background and to adjust terrain-related boundaries;
  • metadata explaining the semantics of all terms, either internally or by reference to external standards such as soil classification systems and laboratory procedures;
  • a users' guide for soil specialists and any interpretations for other uses from the original survey;
and be accessible via internet or optical disk.

Each renewal exercise is unique and must begin with a thorough product specification, user needs analysis and documentation of the existing data. Some aspects are fairly standard (digitizing, geodetic corrections, use of public synoptic data) but may still provide challenges. The most difficult aspect is usually semantic: extracting the meaning from a close reading of the soil survey report and supporting documents, and structuring this into a database design. A data renewal exercise implies a major cultural challenge for most institutions. Especial difficulties are establishing a work flow and quality assurance procedure, training new staff and upgrading current staff. Once soils data becomes available, inter-institutional issues arise, most notably data sharing, data and metadata standards, and responsibilities within a geospatial data infrastructure. This is new territory for most organizations responsible for soil information. Finally, each step of the renewal exercise presents research challenges with links to active research themes in related fields: geodesy, remote sensing, computer science, industrial engineering, and geoinformation science.

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