Here is a quick video of some surveying work I had done on a property earlier this year.
Surveyors use computerized, satellite, and mathmatical methods for determning a points exact location. Many people think that this means just finding the edge or corner of a fence or the wall of a building by finding it's longitude and latitude, but the points must also be defined by their elevation, meaning how above or below sea level they are. In construction this is more obvious because a basement or foundation will go below ground and the structure will go up into the air. For something simple like your backyard fence, this matters because you don't usually actually own what is under you. The mineral rights for most residentail land is owned by someone other than the home owner so the recorded documents showing where your fence is must show that you are building on the surface where you have ownership rights.
Early methods for surveying can be traced back to prehistoric monuments such as Stonehenge, but practical insterments were not invented until the 1600s and were honed well into the 1800s.
Many of the maps and charts we use today in the US are based on work done Public Land Survey System that was established in 1785 to determine and record teritories and devide them into sections of land. This work was so accurate in fact, that many of the same markers existing and are recognized to this day.
Today surveyors must be licensed to do the job and all new data is made public for others to use. The job of surveying usually starts in the office. The surveyor will sometimes spend many hours just researching what is currently known about the land in question and placing surveying points in computers systems that will then help to transfer this information int the field. Once on the land, they use a system of computers that use both GPS and land based radio towers to pinpoint locations. In large cities, surveyors often rely on lasers and other line of site methods since the large buildings interfere with satalites.
Here is a cute video from McKissock land surveying
You can visit them at www.McKissock.com
I don't know anything about this company, I just liked the video.