GRASS users and developers.
In GRASS6.4.2RC3 with wxpython GUI the option ‘Add raster cell arrows’ seems not to work properly. It seems that the arrows in the Map Display cannot zoomed in…
It can be checked by the following steps:
Load and display the aspect (Spearfish) map.
Open the d.rast.arrows panel through the GUI button and choose the same map aspect.
Click Apply: the Map Display appears green as espected for the very high resolution.
Choose 10 for the ‘Draw arrow every Nth grid cell:’ option and none as ‘Color for drawing grid or “none”’ option. The arrows are displayed on the cells of aspect map.
To make the arrows visible choose slope as ‘Raster map containing values used for arrow length:’ and 10.0 as ‘Scale factor for arrows’.
Zoom in a very small area: the cells of aspect map are enlarged, but the density of arrows remains the same
The direction is correctly the same for all arrows inside the same cell but it seems that instead of having an arrow each 10 aspect cells, there is an arrow each 10 pixel of the screen.
Something wrong in my procedure or is this a bug in wxpython GUI (with tcltk GUI the procedure works fine)?
A. Clerici
Parma University