A site map is the drawing surface a job's price comes from: an aerial photo of the lot, or a GC's PDF plan sheet with its scale set, with the areas, lines and counts you trace on it.
Trace the area to pave, the curb line, the crack-fill runs and the stalls, and each shape carries its own number: square feet, linear feet or a count. Drop a service onto a shape and it prices from that number, instead of a measurement retyped into a calculator somewhere else.
The same drawing is what prints on the proposal the customer signs, so what they see matches exactly what was measured.