Hi,
I don't think you've given us enough information for an answer. In many places, "Lambert" coordinates would be from a projected coordinate reference system (CRS) that uses a Lambert conformal conic projection. There is a possibility that a different Lambert projection (cylindrical, for instance) is being used. You've added an Africa tag--can you be more specific? Is the data from a continental map (who published it?) or a specific country or region?
And, what do you mean by normal grid coordinates? Anything projection-based is in a grid. Do you mean using a UTM zone instead? Or do you want 'ground' coordinates, the distances and areas you'd get if you surveyed?
Melita
