Geoscience Reference
In-Depth Information
7 Spatial Data
Braided river system at the northern end of
the Suguta Valley in northern Kenya. The
spatio-temporal analysis of these river systems,
together with their sediment compositions
and provenances (especially in the older
sediments) helps in the reconstruction of
paleoenvironmental conditions.
7.1 Types of Spatial Data
Most data in earth sciences are spatially distributed, either as vector data,
(points, lines, polygons) or as raster data (gridded topography). Vector data
are generated by digitizing map objects such as drainage networks or outlines
of lithologic units. Raster data can be obtained directly from a satellite
sensor output, but gridded data can also, in most cases, be interpolated from
irregularly-distributed i eld samples (gridding).
h e following section introduces the use of vector data by using coastline
data as an example (Section 7.2). h e acquisition and handling of raster data
are then illustrated using digital topographic data (Sections 7.3 to 7.5). h e
availability and use of digital elevation data has increased considerably since
the early 90s. With a resolution of 5 arc minutes (about 9 km), ETOPO5
was one of the i rst data sets for topography and bathymetry. In October
2001 it was replaced by ETOPO2, which has a resolution of 2 arc minutes
(about 4 km), and in March 2009 the ETOPO1 became available, which has a
resolution of 1 arc minutes (about 2 km). h ere is also a data set for topography
called GTOPO30 completed in 1996 that has a horizontal grid spacing of 30
arc seconds (about 1 km). More recently, the 30 and 90 m resolution data
