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Nowadays GPS is very common. So you get positions in latitude and longitude.
But maps are usually not with these latitude and longitude positions. They are based on easting and northing.
One of the methods to transform the latitude and longitude to a easting and northing is with the Transverse Mercator projection.
To do so you need some parameters like:
-latitude of origin
-central meridian
-scale factor
-false easting
-false northing
In this app you can easily change these parameters and calculate the exact easting and northing for any latitude and longitude that you will in.
So the app is very complete. It is an easy to use Transverse Mercator Projection Calculator.