crjw and John Culleton,
Your examples and information were fantastic and useful.
My biggest reason for using printer's points is to sidestep the differences between Gimp's ppi/ppcm v. Inkscape's ppi/ppcm. I use Gimp to clean up scanned images before working in Inkscape. Many older patterns are exactly 1/4th scale, so the Gimp to Inkscape workflow results in a bit of extra work. Gimp uses 72ppi, Inkscape uses 90ppi for the time being.
As John pointed out, the value of 72.72 for a printer's point is outdated. So I did some research:
Printer's points, inches, cm's, mm's, etc. are reconverted back to pixels by each rendering platform according to its own ppi/ppcm definition. So yes, they're always accurate.
Also, Inkscape defaults numeric precision to 8, and will pad numbers with 0's to match the precision setting.
Wikipedia's page http://en.wikipedia.org/wiki/Point_%28typography%29explains that 72.72 was set in 1886, and was changed in 1959. "...The desktop publishing http://en.wikipedia.org/wiki/Desktop_Publishingpoint (DTP point) is defined as 1/72 of the Anglo-Saxon compromise inch http://en.wikipedia.org/wiki/Inch of 1959 (25.4 mm)..."
Still, Donald Knuth http://en.wikipedia.org/wiki/Donald_Knuth used 72.72 in Tex in the 1970's. The inventors of Adobe http://en.wikipedia.org/wiki/Adobe_Systems PostScript http://en.wikipedia.org/wiki/PostScript used 72. This discussion may seem overkill to some, but it does make a difference, and thanks to everyone for pointing out the precision issues.
- Susan
On Fri, Jan 14, 2011 at 3:47 AM, < inkscape-user-request@lists.sourceforge.net> wrote:
Date: Fri, 14 Jan 2011 05:50:38 GMT From: "crjw" <crjw@...2789...> Subject: Re: [Inkscape-user] Inkscape Accurancy
<snip>
Consider the following: -a road map -a circuit board design -a floor plan -a sewing pattern All of these drawings accurately reflect some physical entity. Usually measurements or coordinates of the physical entity are known and can be expressed in standard units such as meters, miles, inches, mils, etc.
My only reason for writing this post is to point out that it is possible to enter coordinates into an SVG drawing in their native values... regardless of how big or how mall the unit is.
<snip>
-crjw