Getting started with spatial data

IBM Informix spatial data types implement the OpenGIS Consortium, Inc. (OpenGIS, or OGC) SQL3 specification of abstract data types (ADTs). These data types can store spatial data such as the location of a landmark, a street, or a parcel of land. IBM Informix spatial data types also conform to the OpenGIS Simple Features Specification for SQL Revision 1.1 and the ISO/IEC 13249-3 SQL/MM Part 3: Spatial. The Informix Spatial solution is based on the ESRI SDE 10.2 Shape and PE libraries.

You use specialized spatial data type functions to compare the values in spatial columns to determine whether the values intersect, overlap, or are related in different ways. These functions can answer questions like, “Is this school within 5 miles of a hazardous waste site?” An application programmer can use an SQL query to join a table that stores sensitive sites such as schools, playgrounds, and hospitals to another table that contains the locations of hazardous sites and return a list of sensitive areas at risk. For example, the following figure shows that a school and hospital lie within the 5-mile radius of two hazardous site locations and the nursing home lies safely outside both radii.

Figure 1. Determining whether sensitive sites are within dangerous areas

You use the ST_Overlaps() function to evaluate whether the polygon that represents the building footprint of the school overlaps the circular polygon that represents the 5-mile radius of a hazardous waste site. The building footprints of the school, hospital, and nursing home are stored in the ST_Polygon data type and the location of each hazardous waste site is stored in an ST_Point data type.