Intersection (computer science)

Under intersection is defined as the superposition of topics levels (Layer) or object classes . There are means of Boolean operations formed new objects that the attributes combine the output objects. The intersection is an important function in geographic information systems .

Example 1: By intersecting cadastral boundaries , addresses and air pollution or noise zones , the people affected can be identified and warned in important cases.

Example 2: Finding the area for a planned landfill: The desired properties are u. a. water-impermeable (clayey) subsoil, fixed distance from settlement areas and bodies of water, as well as a maximum gradient of 5%. By intersecting the layers “Geology” (or soil), “Settlement” (with buffer zones), “Waters” (with buffer zones) and “Slope” ( classification ), you (if applicable) obtain different areas to which the said properties apply. A suitable area can be selected from these based on further criteria.

There are various empirical formulas for estimating the number of polygons resulting from an intersection, here is an example for two layers:

${\displaystyle \mathrm {n} =\mathrm {m_{1}} +\mathrm {m_{2}} +2\cdot {\sqrt {(\mathrm {m_{1}} \cdot \mathrm {m_{2}} )}}}$

with n = resulting area number, m = area number of a layer

A common problem with intersection is sliver polygons .

Web links

• Intersection - English: Overlay . geoinformatik.uni-rostock.de
• Intersection . In: Heinz-Josef Lücking: GISWiki