[GRASSLIST:1180] Re: ps.map pixel size and line attributes
Eric G . Miller
egm2 at jps.net
Fri Nov 24 21:12:26 EST 2000
On Fri, Nov 24, 2000 at 02:00:00PM -0700, Roger S. Miller wrote:
> I'm trying to construct an illustration that contains a large number of
> lines (hydrologic features, roads and a rectangular grid for a ground
> water model) overlain on a raster map showing results from the ground
> water model.
> Using ps.map from version 5, beta 7 I set the resolution of my postscript
> device to 360 (supposedly, 360 dpi) and I specify that the vector files
> should be plotted with a line width of 1 pixel. The line I get is several
> times wider than the 0.003 inch (approximate) thickness that it should be.
> I need very fine lines on this map or the lines obscure each other and the
> model results.
I'm not sure, but I think that width maybe should be "points" rather
than pixels. If that's the case, 1 point = 1/72 inch (according to
Adobe). But I don't know for sure. I don't know what "pixels" would be
in reference to.
> Is there some other way to reduce this pixel size? I tried using
> fractional pixel widths with no improvement. I also tried using the
> "cwidth" specification in ps.map.new and found that the lines in the model
> grid vector file were not categorized, which brings up an entirely
> different question.
> I constructed the file with the model grid from an imported ascii file and
> no attributes file was created when the file was imported. I tried using
> the bulk labeling option in v.digit to label the lines (there are over
> 13,000 lines, so manually labelling them would be inefficient at best),
> but it doesn't work -- no errors are produced, but I get no labelled
> lines. Is there some other way to label the lines? I program; if someone
> can tell me how the lines are identified in the attribute files, then I
> can construct the attribute file myself.
Well, did you try running v.support on the file before doing the bulk
labelling. I think it needs that to work (though it should produce an
error when it can't perform the operation).
Anyway, the line labels are identified by two files. The first:
dig_att/<map> holds a series of entries identified as 'P' for points,
'L' for lines and 'A' for areas. Each entry is then followed by an
easting, northing and a category value. The coordinates of the entry
should fall on the degenerate line for a point, the line for lines, or
within the area (but outside of islands) for areas.
The second file is the dig_cats/<map> file, and after a small header has
n1: Some Label
n2: Another Label
The numbers in the first column connect with the dig_att/<map> file
category numbers. The part following the ':' is the category value.
If you're really interested, there's a programming manual available from
Eric G. Miller <egm2 at jps.net>
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