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I have a fairly high resolution map (jpg, not vector), with a known scale. How to measure the length in pixels between multiple points on an image? For a straight line it is simple, but how to do it when there are multiple points / no straight lines? Is there a simple GIS tool that could do such a thing?

Example:

This can be reduced to 9 legs to get the total length in pixels.

enter image description here

I currently use the measure tool in Gimp, which allows for a maximum of two legs only. This gets tedious quickly (write down the pixels, and then sum the total later), when there are a lot of curves in a road.

Browsing through this Stack, I found QGIS, and installed it. I can import the map as a raster layer, but from that point on I'm not sure what to do. Can I overlay the map with points/lines somehow, to get distances?

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  • Your question is not clear to me; do you want to manually measure distances on a map or do you want to want to connect points with polylines and get their distances? – MarcM Oct 7 '20 at 14:43
  • I have a "flat" map, containing roads and points of interest. Roads are not straight, so I'm looking for a way to measure distances in pixels, which I can convert back to miles. I'll try to rephrase the question to make that more clear. – svenema Oct 7 '20 at 14:50
  • Would the measure tool in QGIS suffice? "Ctrl + shfit + m". This allows you to manually measure your map in your map units. – MarcM Oct 7 '20 at 14:59
  • @MarcM, Nice one. It certainly seems that it will do the trick, provided that it can be tamed into reflecting the correct scale. – svenema Oct 7 '20 at 15:07
  • Unless I'm misunderstanding something you will need to georeference your map to be able to measure distances in QGIS: qgistutorials.com/en/docs/3/georeferencing_basics.html – humperderp Oct 7 '20 at 15:07
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If your map is not georeferenced, you will have to do that first. @humperderp posted a good tutorial on that https://www.qgistutorials.com/en/docs/3/georeferencing_basics.html.

After referencing, the distances can be measured manually in QGIS using the measure tool (Ctrl + shift +m )

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