Here is an interesting mystery sure to drive someone nuts eventually. It seems like it is some kind of strange interaction between d.grid and our rendering algorithms--which have been tested against raster map cells.
impact_wxp1.png shows how a grid overlays single raster cells at high resolution. No matter how I shift the map around with the pan tool or zoom tools, the relationship between the cell and grid stays the same--aligned in the E-W direction and misaligned in the N-S direction. Furthermore, if I use the cursor to view the coordinates in the bottom status bar, the E-W grid lines and cell borders match what is showing for easting coordinates in the status bar when I align the cursor to the E-W grid/cell border. However, in the N-S dimension, the location of the cursor does not match the grid line position, but is about 25% of a cell above it. I don't know if it matches a raster cell border because I don't know what the border value is supposed to be. There is also an error printed (probably unrelated): " Type <grid> of layer <grid> is not supported yet" every time a map is refreshed showing a grid, although the grid displays without problems. Turning to the TclTk display, for all zooming in and out, cells, grid, and cursor position all match up perfectly (impact_tcltk1.png). However, if I subsequently pan around, the cell display and grid no longer align, though in this case the cursor position exactly matches the gridline values in both E-W and N-S dimensions. Michael __________________________________________ Michael Barton, Professor of Anthropology School of Human Evolution & Social Change Center for Social Dynamics & Complexity Arizona State University phone: 480-965-6213 fax: 480-965-7671 www: http://www.public.asu.edu/~cmbarton
impact_tcltk1.png
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impact_tcltk2.png
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impact_wxp1.png
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