I'm a master planner and I want to use QGIS for, among others, importing images (jpg, png, etc without any georeferences). These images will mostly be screenshots of existing structures in Google Earth.
Now when I import such an image the scale and location are far off to what and where I want it. Does anyone know a good method to insert the image on the wanted location on the OSM base layer, translate, rotate and proportionally scale it?
The world file format is the way to spatial reference images. This file usually has the same name as you raster file but use another extension (*.w, *.wld or *.jgw, *.pgw etc). This is a text file with 6 lines:
20.0000000000000 A
0.00000000000000 B
0.00000000000000 C
-20.000000000000 D
424178.117 E
4313415.907 F
This values correspondent to formula:
x1 = Ax + Сy + E
y1 = Dx + By + F
A and D is pixel size in your Spatial Reference values (meters, degrees, etc)
E and F are upper left corner coordinates of your image
B and C - rotation
QGIS accepts this format (don't forget *.prj file with your projection WKT)
Some details is here: https://en.wikipedia.org/wiki/World_file
Since your images are without any georeferences, you can use this QGIS plugin named: Freehand raster georeferencer
In QGIS, open the "Plugins" > "Manage and install plugin" dialog. Install the "Freehand raster georeferencer" plugin.
After installing it, its icons should be added to you tools bar.
If you don't see the icons on your tools bar, go to Raster >> Freehand Raster Georeferencer
Use the icon label as "AD" to add your raster images move them using "MO", rotate using "RO", scale the image using "SC" etc. The plugin works on both QGIS version 2 and 3, see more about using is on the plugin page.
There are some cases we cannot easily create reliable GCPs (ground control points) to georeference our image onto target layer.
I usually use Freehand raster georeferencer to interactively insert such images on my map.
It works like adding an Image Overlay on GoogleEarth.
