Spatialytics ETL's Sextante module is a tool that enables advance geoprocessing by proving various algorithms to simplify, smooth, split and run many other complex processes on geometries. Therefore, this module allows users to transform any geometry at anytime in a transformation by configuring a few parameters and input target geometries.
Note: This module comes as an extra to Spatialytics ETL (contact Spatialytics for more info).
Sextante module is a Spatialytics ETL extension which is not initially included in Spatialytics ETL. Follow these few steps to install the module.
Using Sextante module is pretty much the same as using any other Spatialytics ETL step. The following instructions will guide you to properly configure the module:
Category is not really a parameter but more considered as a way to classify and distinguish algorithms. By selecting a different category, a new set of algorithm becomes available.
Geoprocessing algorithm to be executed. Here is a complete list of these algorithms, categorized by the geometry primitive type (« Category » parameter).
Category « POINT »:
Category « LINE »:
Category « POLYGON »:
Category « GENERAL »:
Most of the algorithms willnot need parameter configuration. However, some of them will need the user to set some parameter values to fine-tune the algorithm. As shown in the next figure, the parameter table is composed of 3 columns labeled as follow :
Here is a complete list of the algorithms requiring such configuration
|Category / Algorithm||Parameter name||Parameter type||Description|
|Simplify lines||Preserve||Boolean||Preserve topology or not.|
|Tolerance||Number||If linestring is shorter than this number, intermediary nodes will be removed.|
|Smooth lines||Intermediate points||Integer||Number of intermediate points to compose the curve.|
|Curve type||String||Type of curve to be applied. Possible values are « Natural cubic splines », « Bezier curves » or « B splines ».|
|Split lines with points||Method||Integer||Split method to be applied. Possible values are « 0 » and « 1 ». Note : This parameter doesn't seem to have any effect in Sextante library.|
|Tolerance||Number||If the distance between linestring and point is shorter than this number, linestring will be split.|
|Simplify polygons||Preserve||Boolean||Preserve topology or not.|
|Tolerance||Number||If a linestring composing a polygon boundary is shorter than this number, intermediary nodes will be removed.|
|Fit N points in polygon||Nb points||Integer||Number of points to fit in polygon.|
|Method||Integer||Spreading method to be used. Possible values are « 0 » to spread points regularly, « 1 » to spread points randomly and « 2 » to spread points regularly with alternance.|
|Transform||Anchor X||Number||Rotation X anchor|
|Anchor Y||Number||Rotation Y anchor|
|Distance X||Number||Translation X distance|
|Distance Y||Number||Translation Y distance|
|Scale X||Number||X scale factor|
|Scale Y||Number||Y scale factor|
|Minimum enclosing polygon||Method||Integer||Enclosing method to be used. Possible values are « 0 » to use a convex hull, « 1 » to use a circle and « 2 » use a rectangle.|
If every algorithm needs at least one geometry field, only a few will require the use of a comparison one. For some algorithms, such as « clip », where the user will need a clipped geometry and a clipper one, comparison step and field is where the second geometry can be input. Here are the algorithms requiring the use of a comparison field :
This step default behavior is to aggregate the comparison geometries into one single layer and then process each reference geometry with the aggregation. By activating this option, each incoming reference geometry will be processed with the single comparison geometry having the same row number, without aggregating.
First, take a look at the following transformation:
In this transformation, Sextante module receives two sets of geometries read from Shapefile files and will clip the linestrings read from the first file with the polygons read from the second.
You can see in the figure above the following configuration: