@Muizer
The problem is that the current version of map has the error of projection (East added by manual work). For example: When the work was carried out with adding objects (adjustment) was very difficult to add the city to make a correction of the river and so on.
The most important:
The sample need to make in real projection ( it will be more easy wark).
Why UTM? Because the material on the Internet is the most common.
For example: SASplanet has access to a variety of sources.
If not UTM then map projection can be any, but real (!). When the need to create a backup copy of the map in GIS (parallel work). However, Mercator metric system is very useful for images and vector data. If we use the Gauss Kruger Proektion, Winkel Tripel or Kavrayskiy proektion - It is a common but at the moment the most popular Mercator system (more sources).
Using the KMZ and KML is generally simplify our work. (Here more UTM good- i work in ArcMap).
With coordinate system (not projection) can be ... latitude, longitude all this we can easily change in any projection.
If we no agreement to UTM projection- So we need to find another map! Not only the raster, but bind (rectification). Also, a height map. With PRJ files (rectification).
UTM not best projection - but more eays work.
If not UTM then we need an another map (rectifying) and a map heights (rectifying).
If we have, then we most easier will be add objects (or make correction)
Or like before ... to make monual work with maps
Sorry for bad english.