How to Use GPS for Land Surveying

Land surveying involves gathering information about the positions of certain points as well as the angles and distance between them. Through the use of certain instruments, surveyors can create maps, establish property lines, and gather important information for architects, engineers, and developers.

The accuracy of land surveying measurements is dependent on the quality of the instruments used to gather the data. With the invention of GPS technology, land surveyors are now able to make complex calculations more quickly and accurately than ever before.

What Is GPS and How Is It Used in Land Surveying?

GPS stands for global positioning system, and it uses signals from satellites to pinpoint a location on the Earth’s surface. In addition to transmitting information about location, GPS can provide data about velocity and time synchronization for various forms of travel. GPS uses at least 24 separate satellites in a system that consists of six Earth-centered orbital planes, each having four satellites.

Generally speaking, GPS has five key uses:

1. Determining a position (location)
2. Moving from one place to another (navigation)
3. Monitoring the movement of a person or object (tracking)
4. Creating a map of an area (mapping)
5. Making precise time measurements (timing)

The Global Positioning System was originally developed for military use but has been readily available for civilian use since the 1990s. In addition to its use in mobile devices and car navigation systems, GPS is used for land surveying.

Surveying was one of the first commercial adaptations of GPS technology. It can provide accurate latitudinal and longitudinal location information regardless of weather conditions and without the need for measuring angles and distances between points. Though GPS makes surveying possible in nearly any location, it does have its limits.

What Are the Best GPS Instruments for Land Surveying?

GPS survey equipment makes it possible to obtain location, distance, and height measurements almost instantaneously – the only requirement is that the instrument has a clear view of the sky to receive signals from GPS satellites clearly. When used properly, GPS for land surveying offers the highest level of accuracy and is much faster than conventional surveying techniques.

Different types of GPS land survey equipment are used for different purposes, though there are three methods of GPS measurement used most often by surveyors:

1. Static GPS Baseline – This method is used to determine the coordinates for survey points by simultaneously recording GPS observations over both a known and unknown survey point for at least 20 minutes. The data is then processed to determine coordinates within 5mm accuracy.
2. Real-Time Kinematic (RTK) Observations – In this method, one receiver remains open over a known point (the Base Station) while another receiver moves between different positions (the Rover Station). Using a radio link, the position of the Rover Station can be calculated within a few seconds, ensuring a similar level of accuracy to baseline measurements as long as they are within 10km of the Base Station.
3. Continuously Operating Reference Stations (CORS) – In this system, a survey grade GPS receiver is permanently installed in a particular location as a starting point for any GPS measurements in the area. GPS survey equipment can collect field data and combine it with CORS data to accurately calculate positions.

Certain instruments are required for proper implementation of GPS land surveying methods. Here is a quick summary of the most common GPS land survey instruments:

• GPS Receiver – This instrument is required to receive signals from GPS satellites in order to make calculations. These instruments come with a variety of optional features such as multiple band channels, built-in Bluetooth and Wi-Fi technology, and OLED displays.
• GPS Rover Rods – These instruments can be used to extend the rover’s reach. They can be made from a variety of durable materials and come in different lengths.
• GPS Poles – Used to mount GPS surveying equipment, these poles are typically lightweight but durable and come in different lengths.
• GPS Bipods/Tripods – For greater stability in mounting GPS equipment, bipods and tripods come in adjustable lengths and numerous sizes.
• GPS Antennae – This piece of equipment makes it possible for GPS systems to receive signals from satellites. Many systems come with an internal antenna, but you can purchase external antennas to boost the signal.
• Total Station – A combination of an electronic theodolite, electronic distance measuring (EDM) device, and software running on an external computer, a total station is used to calculate the coordinates of survey points using angles and distances. It may also incorporate GPS technology to produce more accurate results.

The cost of a GPS land surveying system varies depending on the type and number of receivers you choose. A GPS receiver ranges from $4,000 to over $10,000, and the software itself costs upwards of $400. Additional equipment such as rover rods, poles, and tripods may increase the overall cost.

The Pros and Cons of GPS for Land Surveying

The Global Positioning System changed the world of land surveying in many ways, most of them good. There are, however, some downsides to this type of equipment. Here is a quick summary of the pros and cons for GPS land surveying:

Pros

• It offers a higher level of accuracy than conventional surveying methods
• Calculations are made very quickly and with a high degree of accuracy
• GPS technology is not bound by constraints such as visibility between stations
• Land surveyors can carry GPS components easily for fast, accurate data collection
• Some GPS systems can communicate wireless for real-time data delivery

Cons

• GPS land surveying equipment requires a clear view of the sky to receive satellite signal
• Interference from dense foliage and other structures can limit function and communication
• All GPS survey equipment is subject to failure from dead batteries and system malfunction
• Special equipment may be required and can be costly

The world of land surveying is constantly changing as new technology replaces old. Commercial survey equipment has made leaps and bounds over the past few decades and, with the help of GPS technology, will only become faster and more accurate over time.