You probably replaced your drawing board with autoCAD/ArchiCAD/Revit/SketchUp twenty years ago. Today, hand drafting is still extremely expensive in terms of human time. The cost for a small architectural firm is around €15,000 per year.
In concrete terms, iMapper allows an company to save time in 3 areas :
1. When taking measurements, which is done independently. While it is operating, you can talk to your client.
2. When tracing the plan, which is done like "colouring", without hesitation or transfer of manual measurements to the computer.
3. Eliminating measurement uncertainties that would require a return to the site, or worse, errors that can significantly delay the site.