Oftentimes, there are many equipment options to choose from when undertaking individual surveying tasks. This is also the case when it comes to GPS land surveys.

Capturing geospatial data and making geometric calculations with the touch of a button requires accurate measuring combined with powerful processing. As such, GPS receivers must be able to perform to a high standard while maintaining a reliable satellite connection.

GPS surveys can be used to great effect in a wide range of industries, with a formal background in land surveying no longer being essential to reap the benefits. During the planning stage of a project they can help identify snags without needing to physically visit the site.

In this guide, you’ll find information around the nature of GPS land surveying, in-depth analysis of leading GPS/GNSS survey equipment, and expert recommendations on how to make the most of GPS equipment for land surveys.

Global Positioning System (GPS) survey equipment uses signals from orbiting satellites to pinpoint a location and transmit location data. In order to establish an exact position on the Earth’s surface, a GPS receiver must be able to draw line-of-sight to at least 4 of the satellites that are part of the GPS. Signals are sent from the equipment to determine the latitude, longitude, and altitude of the device respectively. A fourth signal is then used to correct any potential errors in the receiver’s onboard clock.

By using GPS, receivers can determine their position within a couple of metres. While this is impressive considering the distance from Earth of GPS satellites, land surveying requires a much higher level of accuracy. To increase the accuracy of GPS data surveyors can employ various techniques, including:

• Static GPS baseline. By using two stationary GPS receivers positioned at either end of a measurement line, surveyors can determine positional differences with a high level of precision. The devices must be left for at least 20 minutes, after which the collected data can be analysed. This technique is ideal for long-distance measurements on site.
• Real-time observations. An alternative is Real-Time Kinematic (RTK) observations made possible with the use of a base and rover station. Here, the base station regularly transmits correction data to the rover, allowing for rapid data collection with centimeter-level accuracy. An RTK approach is best for data collection on smaller areas that need to be captured quickly.
• Continuously Operating Reference Stations (CORS). This method involves the use of base stations in addition to GPS receivers. The former collects data continuously across a specific area, with surveyors having the option to place receivers anywhere within range. Professionals can then combine CORS information with data gathered by the receiver to achieve accurate measuring and correct anomalies.

By using the appropriate surveying strategy in combination with high-end GPS systems, it’s possible to achieve centimeter and millimeter accuracy.

A GPS land survey is a highly effective method for gathering accurate geospatial data across large areas in a noninvasive way. The main data points collected by a GPS survey include accurate latitude and longitude readings. Although these surveys can also be effective for projects where angular and distance measurements are a priority. A Global Navigation Satellite System (GNSS) survey also uses satellites to pinpoint geo-locations. The key difference is that GNSS devices utilise multiple constellations of satellites whereas GPS equipment makes use of just one.

GPS/GNSS surveying operates using the same principles, however GNSS is typically more accurate and less prone to interference. Read our article Is GNSS better than GPS? for more analysis.

It should be noted that most modern surveying equipment incorporates at least some GNSS technology. It is very rare to find a pure GPS antenna unless it is an older model, for example. So when we’re talking about GPS surveying in this article, this is in reference to both GPS and GNSS systems.

What is a GPS receiver?

Arguably the most important instrument in a GPS land survey, GPS receivers are compact devices that receive and track signals from GPS satellites. The device then converts these signals into measurement data which it uses to determine accurate positioning. Inside most GPS and GNSS receivers are the following components:

• Antenna for capturing satellite signals
• System processor
• Memory for data storage
• Interface
• Connectivity to transmit location data
• Battery power supply

How much does GNSS surveying equipment cost?

The cost of equipment for GPS land surveying will vary depending on the type and number of receivers you need for the project, as well as any additional equipment and GNSS accessories. You will also need to purchase accompanying software to support data processing if you haven’t already. If you’re apprehensive about spending a large sum all in one go, investigating surveying equipment hire can be an effective alternative.

Surveyors can use a wide variety of GPS land surveying equipment when gathering and analysing the data they need. These instruments would include:

• GPS/GNSS receivers
• Total stations
• Bipods and tripods
• GPS antennae
• GPS poles
• GPS rover rods

The exact process of setting up your equipment in preparation for a GPS surveying will depend on what you’re using. That being said, something you’ll need to do as part of any GPS survey is allow your receiver to establish a satellite connection for initial positioning. This is known as the time to first fix (TTFF), which can be influenced by environmental and equipment-related factors.

However, before you start any calibration procedures the first step is to choose your survey location and set up your mount. Be prepared to adapt your approach in respect of site and weather conditions. Once you’re satisfied, make a few trial data collections to test the receiver has established an accurate connection and troubleshoot any other pieces of equipment you’ve brought with you.

Although you will be likely to find various cheap options for GPS/GNSS survey equipment, these should be avoided. This is because there are pitfalls in GPS surveying which will be exposed by the use of sub-par equipment. Here are some examples of GPS surveying receivers which, although more affordable than similar equipment from leading manufacturers, fall short in key areas.

B&G ZG100 GPS Antenna with Integrated Compass and Heel sensor

The data collection capabilities of this unit are simply not comparable to some of the more modern receivers on the market such as the Trimble R750. The key weakness here is that the ZG100 has access to just 32 channels, greatly reducing its flexibility of application in established workflows.

Spherefix SP10

While this piece of equipment is lightweight and features an impressive 1408 channels, its connectivity and tilt sensor limitations let it down. As a result, there will be certain projects where the SP10 won’t be suitable for. As a surveyor, if your equipment can’t produce distance measurements of the necessary accuracy then it is practically useless.

Buying surveying equipment is a long term investment and should be treated as such. You want to consider not only if your project requirements are being met, but also whether a GPS receiver can be used on different projects in the future, its upper accuracy limits, and its reliability expectations. In most cases, you’ll be better off buying a used surveying equipment from reputable brands that has been reconditioned by experts.

The performance, ruggedness, and reliability of your surveying equipment will have a major impact in the overall effectiveness of a GPS land survey. Old products or those without the proper maintenance can be more susceptible to performance drops such as signal disruption, atmospheric interference, receiver limitations, and multipath distortion. The solution is to make sure you only use the very best GPS surveying equipment from reputable brands.

Pros: 

This lightweight and compact receiver has been engineered to maintain its high performance in challenging conditions. What’s more, it’s powered by an RTK that is capable of achieving an accuracy of 8mm (H) and 15mm (V). Featuring over 672 GNSS channels and Trimble 360 tracking technology, the Trimble R12 establishes a reliable satellite connection.

Real time positioning helps surveyors make corrections and adjustments as and when they need to, saving time on site. This product sits at the higher end of the price range for GPS and GNSS receivers.

Cons:

The one notable limitation of the R12 is that it doesn’t contain an internal radio, so separate devices are needed to enable RTK corrections. However, these shortfalls are solved in the Trimble R12i which features its own radio modem and leverages the Trimble RTX positioning service.

Pros: 

The SP85 GNSS receiver from Spectra is a modern piece of GPS surveying equipment that combines an L-band satellite antenna, integrated 3.5G cellular, and WiFi and UHF communications for powerful performance. As a result, this receiver is incredibly reliable when transmitting large sets of geospatial data. On top of this, the SP85 uses patented Z-Blade™ technology to increase potential satellite availability. This can help surveyors save valuable site time when setting up the receiver.

Thanks to the range of features and capabilities of the SP85, it can serve as a versatile turnkey solution when completing GPS land surveys in a range of industries. This includes Construction, Rail Surveying, and many more. As a medium price option, the SP85 is a solid investment for surveyors who complete work in a variety of different settings.

Cons: 

The SP85 is a high-precision instrument that can be susceptible to extreme temperatures and nearby high-power signals. This won’t cause lasting damage to the system but it can prevent it from collecting accurate data. Some users have also reported difficulty in relation to the casing on the SP80 and SP85 model receivers.

Pros: 

If you’re looking for a GPS surveying solution that’s fast, reliable, and easy-to-use, you can’t do much better than the Leica GS18. Due to technology innovations, this product is calibration-free and features tilt compensation that’s immune to magnetic disturbances. Additional multipath reduction works to further improve satellite signal tracking in harsh environments.

The GS18 is an excellent companion to any surveyor that primarily works with a network RTK such as HxGN SmartNet. In these cases, surveyors can make real-time observations supported by impressive interconnectivity and a position update rate of 20 Hz for reliable measurement quality. This rover is a powerful GPS solution deserving of a large price tag.

Cons:

This will be the most expensive option listed here, especially if you opt for a full rover package containing a pole, controller, and rover base. While the GS18 employs self-learning RTKplus technology to help mitigate multipath, it isn’t immune to this form of disruption.

The DA2 is an affordable precision receiver that delivers centimeter accuracy by combining with a Catalyst service subscription. It’s highly portable, with options for either handheld or pole-mounted operation. The DA2 also has impressive GNSS RTK performance which makes it ideal for producing reliable data in proximity to trees and buildings. Advanced ProPoint technology enables precise signal tracking and filtering in even the most challenging environments.

Pros:

The DA2 is a compact GNSS solution that can fit in your pocket. This, coupled with the Android and iOS compatibility, makes it a straightforward option to introduce precision positioning into workflows. The biggest benefit of the DA2 however, is that it’s priced very reasonably. This puts it in comparison with GNSS surveying equipment from overseas manufacturers, although the DA2 has greater compatibility thanks to being part of the Trimble range.

Cons:

The DA2 is a Trimble device that functions best when combined with other products from the Trimble range, which could incur additional costs. Additionally, while this is a modern GNSS receiver, surveyors who require highly degrees of accuracy for their projects could be better off sourcing a more high-end product.

Although we have exclusively talked about receivers and other pieces of surveying hardware, you’ll almost always need accompanying software to support field operations. Trimble Catalyst is a GNSS positioning service designed to deliver precision positioning when combined with the DA2 receiver. The applications for Catalyst include data collection, mobile GIS, land & cadastral management, utilities & asset management, and UAV ground control.

Pros:

Pairs with location-tracking apps on Android and iOS devices for flexible mapping when moving around a site. Low upfront cost for surveying projects, with a range of subscription options to fit your accuracy requirements.

Cons:

The Trimble Catalyst Service App is not supported on Windows 10, 11, Mac OS X, or any mobile operating system below Android 5.0

The Trimble R4 is a complete GNSS system that’s lightweight and cable-free. Its integrated Trimble R-Track technology ensures accurate satellite tracking, while the rugged design makes the R4 a reliable GNSS field solution. What’s more, the R4 is compatible with Trimble VRS solutions, Trimble Access, and Trimble Slate Controller for flexible workflow applications. This piece of equipment can be easily scaled in line with your needs.

Pros:

There are many possible functions for the Trimble R4, including as a VRS rover, RTK rover, or field base station. In each case, the R4 is well-suited to extended use due to its long battery life. It also makes for a simple and convenient solution that’s easy to operate by surveyors of all experience levels.

Cons:

While the R4 is a complete GNSS solution, its performance will likely fall behind some of the more expensive pieces of surveying equipment on the market. Furthermore, operators need to be experienced in order to save time when switching the application of the R4.

GPS technology is commonplace in our everyday lives; it’s in our phones, laptops, cars, and household computers. However, GPS and GNSS systems are far beyond the capabilities of those that are commercially available. The following tips are designed to help with the processing of large and complex GPS data sets.

• Choose your technology carefully – the accuracy of the instruments used to collect and process GPS survey data plays a significant role in the depth of analysis possible. Surveyors must make sure the equipment they have access to can perform the calculations necessary.
• Keep your methodology in mind – when analysing data, you should do so in consideration of the surveying techniques used. This is because it will likely impact how equipment has been calibrated.
• Account for RINEX formats – each type of receiver has its own binary data format. As a result, if your project is using multiple GNSS receivers of different types, you might need to use different software when it comes time to process the data from each.
• Data transfer capabilities – once data has been recorded and collected by GPS receivers or other pieces of surveying equipment, it needs to be transferred off-site for processing. To speed up the overall surveying process, it’s important to consider workflow efficiency. Making use of field equipment with wireless connectivity capabilities will help here.

When it was made commercially available, GPS and GNSS technology revolutionised the surveying industry. Throughout the 2000s and 2010s, many advances were made in the accuracy and adaptability of GPS surveying equipment. At SEP, we’ve remained at the forefront of supplying surveying equipment from top brands.

To capitalise on the continued advancement of equipment for GPS land surveys, surveyors need to stay informed. Hopefully this guide has imparted some useful information around the role of GPS and Precise Point Positioning (PPP) technology in land surveying.

GPS surveys are a powerful option for surveyors that want to avoid an invasive approach when mapping a site. Thanks to technology advancements and the adoption of new techniques, measurement data can be gathered quicker and more accurately than ever before using GPS solutions.

If you have any questions about our range of GPS and GNSS receivers, GNSS accessories, or complementary products, don’t hesitate to contact us. Our team has real-world experience conducting efficient GPS land surveys with leading equipment.