I am an engineer that has to convert northern and eastern coordinates to latitude and longitude coordinates. Does anyone know of an app that will do this. I do not always have Internet access when doing this.

Probably not really what you're looking for ---- but ----- the app UK Maps can display in either northings and eastings or lat and long. If you type in a search in either coordinate system it will take you to that location on the map, you can then switch to the other coordinate system and it will display the current location (that you just searched for) in the new coordinate system.

Tim