Engauge Digitizer - Better Accuracy

To get better accuracy in the digitized output data exported from Engauge Digitizer, it is helpful to understand that all points are only as accurate as the pixel size (you can see that accuracy in the status bar). If the distance in graph units from one pixel to the next is D, then theoretically the best possible accuracy is also D.

It is not possible to define points that are 'between' pixels, even by zooming in closer. That is a constraint imposed by the graphics library that is used in Engauge Digitizer.

Fortunately, there are some tricks to improve the accuracy. In order of increasing difficulty:

• If the axis points are not correctly defined then fix them
• Turn on the grid lines by selecting View/Gridlines Display and compare them to grid lines in the original image to see if the axis points can be slightly adjusted so the grid lines better match each other.
• Use a graphics application like Microsoft Paint (Windows) or GIMP (Linux) to scale the original up in size so each pixel is smaller, and therefore the accuracy of each point is correspondingly better. The larger image is then imported into Engauge Digitizer. This step can be performed using just the command line using the powerful ImageMagick tool.