If you're in the business of capturing accurate surveying data, you’ve likely been using stationary total stations for most of your jobs. Total stations are a tried and true tool in the industry because it can provide down to the millimeter accurate surveying data while in the field. But that accuracy comes at a cost: speed.
Total stations are by their very nature stationary capture devices. Meaning if there are two dozen survey targets that need to be measured on a job site, that's two dozen workflows. That can quickly add up to mean higher costs and more downtime within the area being surveyed. In some situations, they can even put surveyors in potentially unsafe conditions. However, in the past decade advancements in laser sensors and on-the-edge computational capacity has created a new tool for the surveyor toolkit: the LiDAR-based mobile 3D scanner.
Unlike a traditional total station, these mobile scanners can move throughout an area of interest to capture a digital twin from all angles. But this movement often created "drift" – or inaccuracies due to sensor noise – that made the data unreliable. That may have been true some years ago but recent technological advancements in mobile 3D mapping have greatly reduced the "drift" inherent in these maps while increasing the accuracy and allowing mobile mapping to replace total stations in many applications.
Below, we’ll explain what mobile 3D mapping is, how it works, and how recent improvements in online and offline processing has improved the global map accuracy so dramatically. We’ll also explain the use cases where mobile mapping can replace total stations for significant cost savings, faster surveying, and overall improved safety.
You’ve probably already heard of mobile mapping but you may have questions about how it works or how accurate it is.
Mobile mapping allows surveyors to carry a mobile or handheld scanner and simply walk the area that needs to be surveyed. Today’s mobile mapping devices – like Nexys – use a sophisticated algorithm known as SLAM (Simultaneous Localization And Mapping). SLAM technology allows the surveyor to walk freely while still capturing data that is accurate to within millimeters.
Exyn's SLAM technology uses a LiDAR sensor that shoots and captures laser measurements of the surrounding area millions of times per second. Every time this laser light is reflected back to the unit, it creates a “point” of data. When combined, these 3D data points are known as a point cloud and represent the physical area that was scanned.
You can think of a point cloud as similar to a roadside billboard. If you’ve ever seen a billboard up close, you notice the image is made up of thousands of tiny dots. When combined, those dots create an accurate representation of the image on the billboard. A point cloud captured by a 3D mobile scanner is similar, it just uses millions of individual points to create a highly accurate 3D representation of the area.
In its infancy, mobile mapping suffered from a phenomenon known as “drift” that lowered accuracy. However, as surveyors became more familiar with mobile mapping best practices like loop closure and post-processing capabilities becoming more accurate and robust, portable mapping can now be used in many situations that previously required a total station.
Loop closure is when the route of the mobile mapping device intersects with its previous path, creating a confirmation of the SLAM's calculations about its movement through the environment. When the mobile mapping device closes the loop, it can confirm and correct any errors in the point cloud that have been collected. This repeated confirmation and error correction ensures highly accurate data and minimal drift.
Animation showing how SLAM calculations become more accurate with loop closure.
Loop closure is kind of like when you're driving somewhere and you think you might be lost. I know this doesn't happen so much anymore with Google Maps everywhere, but bear with me. While you're driving, you might spot a familiar landmark and suddenly you remember exactly where you are. This feature recognition helps you to take a hypothetical map in your head to 100% confidence you know where you are and where you're going.
Although technologies such as SLAM and loop closure may sound complex, everything happens automatically within a mobile mapping platform like the Nexys without any required input from the surveyor.
We can already see how handheld mobile mapping provides substantial cost savings, time reductions, and improved safety compared to total stations. But SLAM has another trick up its sleeve: enabling autonomous exploration and mapping via robots. Equipped with a modular 3D mapping platform like Nexys, survey teams could send a drone airframe like a DJI M300 on an autonomous mapping mission to capture a critical data set from a dangerous or unknown environment.
Surveyors even have the option to choose their level of autonomy based on mission parameters. For instance, a waypoint based mission could be used to inspect a piece of critical infrastructure while an autonomous exploration mission can be used to map an area of interest from beyond visual line of sight. The main benefit for surveyors is they don't need to be a drone expert to plan or execute these missions. Once they press play, all computation happens onboard the robot, keeping survey teams focused on their critical tasks.
One major benefit of autonomous flight is that the systems automatically perform loop closures as they map an area simply by returning to the same takeoff location. This provides the ultimate in accuracy, and most importantly, a surveyor never has to be within a potentially hazardous environment to get accurate surveying data.
Modularity also provides the Nexys platform with an ecosystem of potentially autonomous robots – like the DJI M300 or Spot from Boston Dynamics. But if you don't need a robot to map, mobile mapping works incredibly well as a handheld or backpack unit. That means one Nexys system can be used for a variety of surveying missions today and in the future.
Below are several areas where mobile mapping can be used alongside total stations to deliver faster results and improved safety by expanding the surveyors toolkit.
Many areas of ongoing construction work will require precise total station measurements, but mobile mapping platforms are becoming critical for quickly capturing large, repeatable datasets for MEP planning and progress monitoring. Whether it’s for progress updates or as-built comparisons needed for regulatory compliance or approval, mobile SLAM saves both time and money over legacy surveying methods.
The flexibility of the Nexys system also fits right into your current surveying workflow. Surveyors can use handheld or mounted to a backpack while still having the flexibility to connect it to an aerial platform for fully autonomous exploration at any time in the future (with an autonomy license).
Because of the low cost and ultra-fast surveying times, you can use mobile mapping for repeatable missions during construction projects or infrastructure inspections. This keeps stakeholders and project managers informed with the latest information so they can make data-driven decisions that save time and keep projects on schedule.
Repeatable surveying missions can also be completely automated using waypoint navigation. With the waypoints set, an autonomous robot will follow the route while intelligently navigating around any obstacles and provide updates at any required interval.
Asset management in unexplored areas can be difficult and even dangerous depending on the environment. Mobile mapping and autonomous exploration improve safety and significantly reduce costs for these mapping situations.
Forestry management is a key task where autonomous exploration provides exceptional benefits. An autonomous robot can quickly map forest density and track trunk sizes or other metrics without the need for surveyors to traverse potentially dangerous environments.
If you want to learn more about mobile mapping and how it can benefit your organization, you can join our webinar on July 2nd, Precision Decisions: Expanding the Surveyor Toolkit with Portable 3D Mapping, or book a free demo to experience our Nexys autonomous mapping solution in action. Our engineers can show you how easily Nexys integrates with your current surveying workflow to reduce costs while giving you the accurate data you need to make critical decisions.
