Map to Gnuplot

Today I was trying to plot the location of some french cities on gnuplot. All I wanted was to map the geo-coordinates of these cities to a [0, 1] x [0, 1] coordinate system. In theory, I could find some data set with the coordinates of these cities and make a simple python script to convert them to my system. However, I need very few cities and discarding the others would require some manual cherry picking.

So I was looking for some online application which would allow me to draw points in a coordinate system which range could be configurable.
I wanted to manually draw the points for each city (by putting a map on top of the screen) and retrieve the coordinates. Unfortunately, I didn’t find anything suitable which would accomplish this in an easy way.

Therefore, I opted for implementing it myself using d3js. Here is the result.

By feeding these coordinates to a gnuplot script, I obtained this:
france

Which is pretty much what I wanted. You can find the all-in-one code in the following gist.