units accuracy

The values shown for X, Y, W and H on teh bar below the meny differ from those in the xml document.

I proceed as follows:

- create a new inkscape doc in inkscape .svg format
- draw a singe streight line in the doc
- save the doc
- no other changes to settings are made. units in the pull down list on the bar below the menu bar are set to px (default)
- open the doc in notepad
- Output significant digits were set to 12 to try and eliminate rounding errors.

Problem: the notepad doc gives the path values as: M 174.285714286,620.933633296 342.857142857,466.64791901 whereas the on screen bar below the meny bar give teh values- X: 173.948 Y: 431.060 W: 169.247 H: 155.023

This is an error of .338 px (0.2%) which is significant - prohibitive for my application.

I have read much in the manual and FAQ and googled plenty, and tried all sorts of combinations of 90 vs 96 pixels per inch etc etc, to no avail. As an electrical engineer I should be able to understand from the documentation, but seem not to be able to sort this out or even understand the problem. Perhaps i'm loosing my touch.

Please can someone assist.