Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Scale measure
#1
Fairly basic user, trying to measure off of scanned mapping where the scale is all to cock.

Is there any way to use the measure tool, or another tool, to set a scale and measure using it - i.e. can I log points x and y, tell the tool that's 100, or whatever, and then have it automatically scale any further measurements to that?

So, on a map, I could click either edge of a grid square, which is - say - 336 pixels, and log that as 1000m, then measure a line somewhere else, let's say 512 pixels, and have the measure tool automatically tell me that's 1524m, without me having to break out the calculator for every measurement?
Reply
#2
See Image>Print size. The "print definition" is just an arbitrary ratio of pixels/unit of length. It is sometimes acknowledged, once in a blue moon, to be the size at which you want the image printed, but it has other uses.
  • With Gimp's measure tool (Measure) measure (in pixels) some distance/length in your image between two points for which you know the real distance
  • A simple division (length in pixels / physical length) gives how many pixels to the cm/metre/yard/furlong you have in your image.
  • Enter these values in the print definition dialog,
  • Change the display unit in the small indicator at the bottom left of the image display.
  • From now on all measures (Measure tool, but also rulers, guides...) are in physical units.
Reply
#3
(02-15-2018, 01:42 PM)Ofnuts Wrote: See Image>Print size. The "print definition" is just an arbitrary ratio of pixels/unit of length. It is sometimes acknowledged, once in a blue moon, to be the size at which you want the image printed, but it has other uses.
  • With Gimp's measure tool (Measure) measure (in pixels) some distance/length in your image between two points for which you know the real distance
  • A simple division (length in pixels / physical length) gives how many pixels to the cm/metre/yard/furlong you have in your image.
  • Enter these values in the print definition dialog,
  • Change the display unit in the small indicator at the bottom left of the image display.
  • From now on all measures (Measure tool, but also rulers, guides...) are in physical units.

You beautiful beautiful person, thank you so much
Reply
#4
Ofnuts saved me some writing, screenshots to go with the text.

https://i.imgur.com/S8O4QA2.jpg

To a certain extent Gimp will do the arithmetic for you / (divide) and * (multiply) work in some dialogues
https://i.imgur.com/Y82iC2u.jpg

There will be rounding errors, not going to be millimetre perfect.
https://i.imgur.com/VfsrDzy.jpg

Remember to reset the print resolution if you ever want to print the image, or you will need a large sheet of paper Wink
Reply
#5
So am I correct in assuming that, given I am not interested in the print size but and eventual bmp and dds file which will result in the correct size in those files when I am working with them and a Gmax file I need to make, I would use the same technique?. This is to do with making airfields for a simulation based on actual sizes.

 I would be using files 4096 x 4096 ans would make the ordinal map or drawing the same size for measuring?
Reply
#6
Not sure what you need / if it is possible.

There is a unit editor, bottom of the edit menu, where you can add your own units for the rulers/measure tool.

As well as the unit editor, the settings are held in the unitrc file in the Gimp profile. It says not to edit but of course you can.

After messing about, I still can not get my head around how the scale factors work. What I think is logical ie 1000m = 39.37 x 1000 inches does not work.

A crazy value of 1 (same as an inch) gives me a km scale. On a map example, I can measure  in km. 

However, you still can not escape print size and ppi. Your 4096 x 4096 canvas @ 96 ppi comes up at 40 km square, so you will need to set some large ppi value to get a desired size.

Not difficult but messy. you will just have to experiment (if that is what you want)

   
Reply


Forum Jump: