Surveying has changed substantially over the years — what used to take months of observation, measurement and geometrical calculations now takes a few hours or days thanks to the introduction of GPS technology. In fact, the surveying industry was one of the first to utilize GPS technology, recognizing the potential benefits of the technology. Today, surveying professionals rely on GPS to provide accurate and reliable data for clients across a wide range of industries and applications. Despite the widespread usage of GPS technology in surveying, however, it’s not a topic many know about — that’s why we’re here to explain the GPS surveying basics.
Decoding GPS Surveying: An Introductory Overview
To understand the GPS surveying process, you need to understand what GPS is. In short, GPS, or the global positioning system, is a satellite-based navigation system. GPS was first developed for military use starting in the 1970s and became fully operational in 1993. Since then, it has expanded its use to consumer and commercial applications.
GPS uses a network of satellites, which communicate with receivers on the ground. When a receiver requests data to calculate its location, four or more GPS satellites will communicate with the receiver, sending the position of the satellite, the time the data was transmitted and the distance between the satellite and the receiver. The information collected from these satellites then calculates the latitude, longitude and height of the receiver. If the receiver is moving, continuous data collection can be used to calculate the changing position of the receiver over time, which can be used to calculate speed. No matter the weather conditions or time, GPS can triangulate the signal and provide a location.
While most people are familiar with GPS and have used it to some degree on their smartphones or car navigation systems, GPS is a powerful tool for commercial applications. It’s particularly useful for the surveying industry. Surveying was one of the first commercial adaptations for GPS for its ability to obtain latitudes and longitudes without the need for measuring distances and angles between points. In combination with other surveying equipment, like the Total Station, GPS technology provides valuable information for surveyors to help develop plans and models for client projects.
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Exploring Methods of GPS Surveying: A Step-by-Step Guide
GPS surveying uses similar technology to nearly any other GPS application — however, how surveyors use GPS differs significantly. The primary differences are in two areas — technology and usage.
- Technology: Surveyors use more sophisticated technology than typical GPS applications to increase the accuracy of the data they collect. The receivers used for surveying are significantly more complex and expensive than those you would find in a typical car navigation system, with high-quality antennas and more sophisticated calculation technology.
- Data Usage: The data surveyors collect from the GPS technology is used differently than in a typical navigation system — instead of using location data for navigation, the data is used for measuring between two points. These measurements are collected then stored, manipulated and displayed in a geographic information system, or GIS, for use in a survey model.
But how do surveyors use GPS to collect data? The specifics come down to the GPS surveying techniques that they use. While the basics of GPS are simple to understand, there are several techniques that surveyors use to make the most of the GPS measurements they collect. There are three primary methods of GPS measurement that surveyors use, which are listed below.
Method I: Static GPS Baseline Observations
A Static GPS Baseline is a technique used to determine accurate coordinates for survey points. Baseline measurements achieve this by recording GPS observations over time, then processing that data to provide the most accurate result.
The technique works by using two GPS receivers. These receivers are placed at each end of a line to be measured. The receivers then collect GPS data simultaneously for at least 20 minutes — the exact duration of the observation period varies based on how long the line is and how accurate the measurements need to be. Once all of the data is collected, a special type of software is used to calculate the difference in position between the two receivers.
This GPS surveying technique is basic but highly useful and accurate, especially when measuring particularly long distances. Because the GPS data is collected over a long period of time, and the observations are collected at the same time at each end of the baseline, the natural distortions that occur in GPS signals cancel each other out. Generally speaking, the accuracy of Static GPS Baseline measurements are one part per million, meaning that a 30 kilometer distance can be measured with about 30 mm of uncertainty.
Method II: Dynamic GPS Observation Methods: RTK
Real-Time Kinematic or RTK Observations are similar to baseline methods in that they are used to measure distances between a base station and a second receiver. The difference, however, is that instead of measuring the location of two points over a long period of time, RTK Observations use multiple points in quick succession.
Like the baseline method, the RTK method uses two receivers, one being a static base station. The other receiver is the Rover Station, which moves to multiple positions during the measurement period. The position of the Rover Station is collected within a few seconds and stored. Once the measurement period is complete, this data is stored and used as survey data.
RTK observations are nearly as accurate as the baseline technique, though they are limited to a range of about 20 kilometers. This method maintains a high level of accuracy by collecting data at the Base Station and the Rover Station simultaneously and correcting data in real time — the exact position of the Base Station is known, so any variations can be used to correct the position of the Rover Station in real time. This method, therefore, can quickly gather survey data for smaller areas.
Method III: CORS—Extending GPS Capabilities
Continuously Operating Reference Stations or CORS operate using the same principles as the other measurement techniques described. The primary difference is that the base station is installed in a permanent known location. This allows measurements to be taken at any point in the district using the permanent base station as a starting point.
With a CORS-based system, receivers can be placed anywhere in the local area to collect data. When data collection is complete, the surveyors can combine the collected data with data from the CORS to calculate positions, correcting any anomalies to obtain an accurate position. In some cases, if multiple CORS are available, receiver data may be compared to the data of multiple CORS to achieve even more accurate results.
CORS are commonly used for major engineering projects that require continuous surveying over a long period of time — some examples include local government projects, mining sites and tectonic plate studies for scientific organizations. One specific example is the Australian Regional GPS Network, or ARGN, which uses an online processing system to provide positions that are accurate within a few centimeters in under 24 hours. Some countries even have CORS systems that cover their entire nation, allowing for more accurate and reliable GPS positioning anywhere in the country for both commercial and consumer applications.
Professionals Who Utilize GPS Surveying Techniques
GPS surveying is a quick and accurate way of mapping and modeling the physical world, from mountainous landscapes to city skylines. This versatility and utility are why GPS surveying is the standard practice for any surveying operation. Nearly any group that needs surveying done will use GPS surveying, including government organizations, scientific groups or commercial businesses. Some of the benefits these groups enjoy from GPS surveying include:
- Flexibility: Unlike conventional surveying techniques, GPS surveying can function regardless of visibility. If survey stations are out of each other’s sight due to line-of-sight issues or weather, GPS technology can still measure their positions and provide accurate location data. This is particularly useful when surveying coasts and waterways with few land-based reference points, which is particularly helpful for nautical navigation and construction efforts. The only downside is that GPS stations need to access satellites with a clear line of communication, limiting the utility of GPS surveying in areas with trees or tall buildings.
- Mobility: GPS systems are fairly mobile, able to be carried inside backpacks or mounted on vehicles to collect data quickly and over a wide area. In combination with CORS systems, mobile GPS survey equipment can achieve real-time data.
- Speed: GPS technology is extremely quick compared to the old surveying techniques that relied on extensive measuring and calculations. Now, GPS provides near instantaneous data and can automatically compare that data to provide accurate results quickly, sometimes even within a few minutes. With faster data, survey teams can get quicker results and organizations can reduce decision time.
- Accuracy: The ultimate question stakeholders are concerned about is the accuracy of GPS survey equipment. Ultimately, it depends on who does the surveying. Poor equipment and inexperienced users can negatively affect your accuracy. However, when using sophisticated GPS technology combined with top-level expertise and high-quality software, you can achieve high levels of accuracy every time.
These benefits are the primary reasons many companies choose GPS surveying specialists for their surveying needs. However, all this data is meaningless without context. For almost all industries, GPS survey data is combined with sophisticated 3D modeling to create detailed, actionable data that organizations can use to plan their projects. This 3D modeling data not only allows companies to visualize and plan projects, but it also allows for 3D model machine control for construction projects.
3D machine control uses positioning sensors to give machine operators feedback on their equipment, directing them in how to use the equipment to achieve the desired results. This technology promises to be the new standard for efficient worksite operations, improving the accuracy of construction equipment on site. For more information about GPS machine control modeling, contact Take-Off Professionals or look through our site to learn about our services.
Industries Integrating GPS Surveying for Enhanced Accuracy
Almost any industry that needs surveying will choose GPS surveying for its high level of accuracy and utility. One of the biggest sectors using GPS technology is the construction industry — construction companies need fast, accurate survey results for their projects so they can start and finish projects quickly and confidently. Some of the biggest industries in the construction sector needing GPS surveying technology include:
- Commercial Site Industry: Data is essential in the commercial site construction industry at every level. Commercial site construction companies need accurate, useful data and models to create cost estimates, organize their resources and improve overall efficiency. GPS survey data can help, providing accurate results quickly so that commercial site companies can make decisions that improve their profitability.
- Roadwork and Highway Industry: Engineers and contractors in the roadwork and highway industry need accurate survey data from start to finish. Quality surveys help create accurate models, which roadwork and highway professionals can use to place accurate bids, plan projects and organize their resources efficiently to maximize their profitability. On top of it all, roadwork professionals need to get it all done quickly to minimize the inconvenience and cost to the people using those roads. GPS surveys are essential in these efforts, providing quick, accurate results for models so that roadwork professionals can get to work as quickly as possible.
The key for both of these industries, however, is choosing to work with companies that can help them achieve the results they need. Not only do they need professional surveyors, but they need next-level data modeling professionals to help create effective 3D models that can help them plan more effectively and even make use of 3D machine control. Take-Off Professionals can help.
Best Practices for Effective GPS Surveying Work
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Take-Off Professionals, or TOPS, is a team of knowledgeable and experienced professionals specializing in the preparation of 3D models for site work. Our team of licensed engineers, surveyors and 3D technicians handle projects for large and small projects across the commercial site and roadwork and highway industries, delivering quality results every time. Our innovative processes put quality data at your fingertips, giving you the confidence you need to bid, organize and complete projects while maximizing your profits and efficiency.
Over the course of two decades, TOPS has become a data industry leader, producing an average of 1000 models per year with accuracy to three digits for imperial units and four digits for metric units. Our unique industry experience gives us insight into the concerns of our clients, allowing us to quickly adapt to client needs and address any issue so we can deliver effective, accurate and fast results every time.
On top of it all, TOPS makes your satisfaction our priority. We deliver detailed quotes, accurate turnaround times and top-quality customer service for every project, and we stick to our promises every time. Let us know what you need from your data, and we’ll make it happen.
Interested in learning more about our industry-leading processes and how they can help your business achieve more? Contact TOPS today by calling 623-323-8441 or through our online contact form.