Backward pathline calculation for steady vector fields in Quantum GIS

Calculating backward pathlines in steady vector fields is possible using the new version of VectorFieldCalc, a Python plugin for Quantum GIS. The pathline calculation is implemented via the Runge-Kutta-Fehlberg method (see references at the end).

For forward calculations, the user defines positive values of time steps and total times. For backward calculations, use negative values for both total time and time steps. An example for the last case, using the example data provided in the plugin folder, is below.

The result of the backward pathline calculation is presented in the figure below, with pathline points symbolised by increasingly negative total time, together with labels of the total times. The flows in this Antarctic glacier in Terra Nova Bay (data from D. Biscaro PhD thesis) are from top-left to bottom-right. Higher velocities of the flow field are in red, lower velocities in blue. Starting points are represented by red squares in the bottom-left section of the glacier.

 The plugin can be installed via the usual procedure for Quantum GIS, using the plugin manager.

For additional details (based on the previous version) you can see:
- Vector Field Processing
- 'Vector field processings': un plugin Quantum GIS per l'analisi di campi vettoriali 2D (in Italian)