A survey of the selected site by a person (Preferably a Professional Surveyor) resulting in a 1: 100 Plan showing the slope of the land by means of Contours; being lines drawn to represent all points of the same level (height) above a Datum Point of 100 00 that is often a mark on a fixed object (eg Concrete kerbing) adjacent to the site If the allotment has not been secured financially, permission should be sought from the Owner or Agent to enter onto the site, for this purpose