In QGIS 3.4, I am using the Print Layout to print some UTM lines with scale bars. My goal is to make a PDF of a map that is at 1:63360 or 1 inch to the mile.
When I print the PDF, the mile Scale Bar does not measure out to be one full inch. I have ensured that I am not introducing scaling during the print rendering; that is, I print at 100% scale from AirPrint in the macOS Preview.
Other useful Info
Edit — Root cause found
The problem arose because I copy/pasted the legend from Map
A to Map
B. My guess is when pasting the new legend object into Map
B preserved the scale from Map
- I have added three Scale Bars to the layout that appear to be working as expected.
- Km - Single Box, colored in yellow
- Miles - Line Ticks, in black
- Numeric, which shows the scale ratio —
- Importing the PDF into GIMP and setting the resolution to 300 yields these measurement
- Km is 220 px at 300 dpi = 0.73" when printed
- Miles is 360 px at 300 dpi = 1.2" when printed already wrong
- But, the ratio of
360 px for 1 mileto
220 px for 1 Kmor
360/220is approximately 1.6. Therefore, the Scale Bar are correct when generated from QGIS. The measurement errors in pixels is due to me drawing a line in GIMP, so I'm not too worried about that difference.
- I've tried the following projections which both yield similar errors of
one mile not equal to 1"