Many disciplines work with spatial data, and many people use a GIS to reference geo-spatial data. Starting with a concise definition of spatial data, this topic describes how spatial data and their accuracy are related to the measurement process and one’s choice of a measurement system. The goal is to describe how 3-D spatial data can be manipulated more efficiently and how spatial data accuracy can be established without ambiguity using the GSDM as the foundation for GIS’s and the GSDI.
Modern practice and instruments are used to collect and record spatial measurements. These data are processed electronically, and digital results are stored in computer files. Paper maps are inherently two-dimensional (they flatten the Earth), and humans traditionally view spatial relationships in terms of “horizontal” and “vertical.” Computer graphics and data visualization procedures offer an endless array of display options. Although not exhaustive, this topic summarizes characteristics of pertinent coordinate systems, defines spatial data, and looks at measurement processes by which spatial data are generated. Today, 3-D digital spatial data are more appropriately stored in a database that combines horizontal and vertical into a single database. And, as discussed later in this topic, differences between how spatial and geospatial data are used may become significant. The accuracy of spatial data is also considered, and an important distinction is made between primary and derived spatial data.
