GPS - Global Positioning System is a network of satellites system run by  the U.S. government which constantly send out the time and their  position, the difference in time when the signal is received multiplied  by the speed of light gives the distance between the satellite and the  receiver and the distance from 4 satellites enables a 3D position of the  receiver to be calculated. Due to differences in atmospheric  composition, errors in satellite position and clock errors the best  accuracy achievable using this method alone is only 2-5m. 

Topographic Surveys are used to identify and map the contours of the  ground and existing features on the surface of the earth or slightly  above or below the earth's surface (i.e. trees, buildings, streets,  walkways, manholes, utility poles, retaining walls, etc.).  If the  purpose of the survey is to serve as a base map for the design of a  residence or building of some type, or design a road or driveway, it may  be necessary to show perimeter boundary lines and the lines of  easements on or crossing the property being surveyed, in order for a  designer to accurately show zoning and other agency required setbacks.

Yes, we can provide accurate site areas which can aid when purchasing  land. We can also accurately set out the areas if disputed or if land  titles are divided. If you require the volume of material measured we  can provide it, we undertake many stockpile surveys and have extensive  experience on landfill sites.