The Use of DEM and Satellite Data for Regional Scale Soil Databases
Authors: Dobos Endre , Norman B. , Worstell B. ,   et al.
Published: August 2004

New, quantitative
methods and data sources for characterizing small scale soil resources have
been demonstrated. AVHRR and coarse spatial resolution DEM were designed for
mapping large areas of the world quickly and cost effectively. The method
combines digital elevation data, “ground truth” information, including the soil
taxonomic class for measured soil locations, and a time series of satellite
images to form a digital soil database. The results show that using ancillary
information such as AVHRR data and DEM derivatives from the national to
continental level surveys is among the most promising tools for geographers and
soil surveyors. The AVHRR data is often used for land cover studies but its
usefulness in soil studies has not yet been proven. This study is a
representative example of the usefulness of AVHRR data in characterizing the
soil-forming environment and delineating soil patterns, particularly when
integrated with other data for describing the soil landscape, such as the DEM,
slope, curvature and PDD. The predictive power of AVHRR and similar low spatial
resolution satellite data sources could be further improved with the
development of soil sensitive filters. Mention should be made of the potential
improvement of the products derived from these data sources with the use of
better quality data provided by satellites that have been launched recently.
Neither the AVHRR nor the DEM-derivatives show high correlation with the soil
classes, but both represent a great portion of the environmental variability.
In general, the more uncorrelated information is extracted from DEM and AVHRR,
the better explanation of the spatial soil variability is achieved with an
integrated use of them. The images of AVHRR time series show a relatively low
correlation, thus each of the new dates adds much potential information on the
soils. The studies also highlighted the great help of surface vegetation in
soil remote sensing, as indicated by the high R² value of Band 1 and NDVI.
The importance of the short-term weather history of the study area was also
demonstrated.  Terrain information and
terrain variables were primarily developed for large scale local studies. Small
scale mapping of large regions presents different issues, like over-generalization
and over-smoothing of the soil information. The terrain features with smaller
extents are dissolved into a larger neighborhood. As a smoother terrain map is
created, a lot of detail is lost and less variability is observable. Many of
the terrain attributes are useless with this approach. Elevation, slope, relief
intensity, potential drainage density and the curvature variables are the most
informative digital variables for characterizing the soil-landscape in small
scale inventories.  The resulting soil
databases will have all the advantages of quantitatively derived databases,
including consistency, homogeneity, and reduced data generalization and
edge-matching problems. Although the results from the above procedures are
believed to be accurate enough to serve as a basis for global and regional
studies, they should be checked and further revised by local and regional
experts to ensure quality. Research should continue on improving the
procedures, augmenting the pedon data with new field sampling, and
incorporating new image and DEM data sources. One of the most important results
of these studies is the demonstration of the usefulness of these data sources
for small scale soil mapping and the overall validity and representatitivity of
the AVHRR-terrain/soil correlation within the temperate region of the world.
Further studies will need to be performed to test the use of AVHRR and terrain
data for other climate zones of the World, where potential problems, like
continuous cloud cover, may occur.