Full textIt is important to understand that most of the analyses in a GIS are done by using algorithms. Where the simple questions and calculations can be executed by using standard SQL syntax to query your data, this is not sufficient for the more complex computations. Questions that involve spatial attributes for example will often need an algorithm to get the answer. The basic concept of an algorithm is that it is a mathematical procedure with a stepbystep structure, which allows the user to define variables in different stages of its execution to determine the outcome. If you would use an algorithm to interpolate a value between points a and b (calculating a value on a given point between a and b using the values of a and b), you would for example be able to attribute a greater importance (weight) to point a (because you might know the value for point a is valid for a greater range) to ‘weigh’ the outcome. Algorithms used in GIS software can vary highly, depending on their exact purpose, the version and the person/company that produced them. It is therefore important to realize that the same algorithms in different GIS packages can have different outcomes, and it is therefore obligatory to always explicitly name to algorithms used to obtain your datasets.
