I recently asked a question about a coordinate system in a file, and found out that it used SWEREF99TM, but I can't figure out how to convert those coordinates to the "geographic coordinate system". I've found a bit about it on lantmateriet.se. It says that:
It is an advantage for many different applications at the national level if the whole Sweden can be mapped seamlessly, i.e. on one projection with position given in one co-ordinate system. A rigid application of, for example, UTM in Sweden would require a division into three zones.
The definition of a dedicated projection based on a meridian 15° E of Greenwich, with a scale factor of 0.9996, with the Equator as the origin for N co-ordinates and with E co-ordinates measured from the central meridian and increasing eastwards (the central meridian is assigned a value of 500 000 m to avoid negative values) will give consistency with UTM in the major part of the country.
I still can't really figure out how to convert it, but I would be glad if someone could help me with it. I got a suggestion to use the java library proj4j (because I'm going to convert it using java, and then use the coordinates in an android app).
But I can't figure out how to use that either, and I also want to do it myself. I don't really like libraries. I want to do stuff myself. Don't know why. It just is like that :)
What does the scale factor mean, and what unit is the coordinates measured with, and so on.