Spatial Data

Abstract

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 field samples (gridding).

The following section introduces the use of vector data by using coastline data as an example (Section 7.2). The acquisition and handling of raster data are then illustrated using digital topographic data (Sections 7.3 to 7.5). The availability and use of digital elevation data has increased considerably since the early 90s. With a resolution of 5 arc minutes (ca. 8 km), ETOPO5 was one of the first data sets for topography and bathymetry. In October 2001, it was replaced by ETOPO2, which has a resolution of 2 arc minutes (ca. 4 km), and just recently the ETOPO1 became available, which has a resolution of 1 arc minutes (ca. 2 km). In addition, there is a data set for topography called GTOPO30 completed in 1996 that has a horizontal grid spacing of 30 arc seconds (ca. 1 km). Most recently, the 30 and 90 m resolution data from the Shuttle Radar Topography Mission (SRTM) have replaced the older data sets in most scientific studies.