Land surveying is a technique in which professionals look at land and identify accurately the three dimensional positions of points and the distances between them. This is often used in order to calculate the data needed for maps, and in order to set boundaries of ownership. It can also be used for general mapping and there are many land surveying initiatives run by the government.
To achieve this surveyors will use geometry, engineering, mathematics, physics and law to understand the exact nature of land, who it belongs to and what can be potentially done with it. They will often have a background in geography that will help them to recognize land types and how maps and mapping works, but this is largely a very mathematical process that requires a very in depth understanding and a lot of knowledge and skill. It is not something that you can do easily yourself then!
Another definition for land surveyors is supplied by the American Congress on Surveying and Mapping (also known as ACSM). Here it is described as the science or art of making the measurements needed to determine relative positions of points and cultural details on the surface or below the surface of the Earth, and the ability to depict them in a readable format. In other words then surveyors are used to create all kinds of maps and information regarding a piece of land in three dimensions for access by a range of different services.
GPS land surveying is essentially this process but using GPS in order to achieve the end. GPS stands for ‘Global Positioning System’ and you are no doubt aware already of this system as it is used crudely in a range of every day applications now – from navigation systems in cars, to maps and directions on smart phones. Most likely you have at some point used GPS to perform what is essentially a form of surveying in order to retrieve information mapped by other surveyors.
GPS works using satellites. These satellites move around the Earth in geosynchronous orbit meaning that they stay in the same position relative to the Earth – moving in accordance with the Earth’s natural rotation. The system you carry on the ground then works by sending a message up to those satellites, and when the satellite receives them, they send them back down for your device to receive. Your device then uses the amount of time that the exchange took in order to calculate the distance from that satellite. Of course doing this wouldn’t be sufficient for precise surveying, and so in fact a GPS device will send a message to lots of different satellites at once and will then be able to calculate the relative distance from all these points. Then, using this information it can ‘triangulate’ its precise location. Triangulation is in fact a method that has previously been used in surveying, but thanks to GPS surveying it is now incredibly easy and has been made largely obsolete. Of course GPS can make many aspects of surveying much easier, but likewise it is surveying that makes GPS possible.