Drone Surveying vs Traditional Surveying

Let's get straight to it: Drones have revolutionised surveying - collecting accurate data quicker, easier and safer than traditional ground-based methods.

After all, why spend time manually obtaining data - traversing a potentially-dangerous job site in the process - when a drone can do it for you. 

But don't just take our word for it, because this streamlined and effective process is validated by surveying professionals around the world:  

• Cost Savings: "Drones enable firms to create highly-accurate maps and point clouds, discover costly job-site mistakes, and predict schedule delays, saving up to tens of thousands of pounds per week,” - Richard Clement, Komatsu.
• Time Savings: "Using drones, we’ve created a much more efficient process. We can literally take weeks out of the schedule, our projects are much higher quality than before, and they’re safer," - Jim Gorrie, CEO Brasfield & Gorrie. 
• Streamlined Project Management: "Drone footage helps streamline project management. It only took my team a few days to complete site mapping with drones, accelerating project planning with more accurate site data," - Grant Hagen, VDC Manager, The Beck Group.
• Improved Safety: "Drones significantly reduce the number of workplace hazards exposed to employees," -  Alexander Tubaltsev, Chief Miner, Ferrexpo Yeristovo Mining.

It's impressive stuff, highlighting, in a nutshell, how drones compare to traditional methods of surveying. 

In this article, we take a deep dive into the differences between manual, ground-based traditional surveys and automated, aerial drone mapping and find out why UAS has transformed data collection workflows on AEC industry job sites. 

Drone Surveying vs Traditional Surveying: Survey Speed

When it comes to speed, there's only one winner. To put it simply, drones are a far more efficient data capture tool. 

For instance, Alexander Tubaltsev, Chief Miner at Ferrexpo Yeristovo Mining, concludes that using drones to collect stockpile measurements is up to 90% faster than manual methods.

And this table below presents an indicative comparison between a ground-based survey and an aerial drone one. 

The table shows there is a major difference in speed between drone surveying and traditional methods: We're talking days instead of weeks on large sites. And in some cases, on smaller sites, these efficiencies are accelerated, with one, sub 30-minute drone flight collecting the necessary data.   

As Craig Matthews, of Balfour Beatty, says: "Drones are a great time saver. Take one of our recycling compounds, for example. It would take a surveyor, using traditional handheld equipment, about a day to measure the stockpiles and process the data. But using the drone, we can fly over the compound in 15 minutes and process the model in about two hours."

There's several reasons why drones can collect data quicker.

Firstly, drones can cover larger areas in less time. For instance, the DJI M300 RTK drone and P1 photogrammetry camera combination can cover up to 7.5km² per day. That's huge! Imagine how long this distance would take to cover on foot.

Secondly, drone surveys do not require a team to walk a survey site with a total station and conduct manual measurements. Nor do they require a team to lay out huge numbers of ground control points. Understandably, both of these are time-consuming jobs.

Instead, a drone can collect these measurements autonomously, following a pre-set flight path which can be quickly set by the pilot by using the drone's corresponding flight app.

And the inclusion of RTK on DJI drones such as the Phantom 4 RTK and M300 RTK, ground teams do not need to lay out as many GCPs. In fact, the M300 RTK - with its dual-antenna RTK modules - makes a GCP-free surveying operation, possible. 

Drones Capture Your Entire Site

One of the biggest advantages of drones is that they can be used to collect site-wide data in just one flight, with all of information contained in a point cloud or orthomosaic photo.

Not only is it an efficient way of collecting vast quantities of data, but it also means that all the information is gathered in one go, instead of conducting a ground-based survey, only to find out that it needs to be redone because part of the site has been missed.

And even if you don't need part of the data set immediately, it can be stored in the cloud ready for when you do, without the need for additional field work.

These site-wide maps can provide a range of information, too.

For instance, this geo-referenced 2D orthomosaic showing SUEZ's recycling centre was captured during a single 15 minute flight with the Phantom 4 RTK. 

In just one image, the team can identify problems, track productivity, decide where to deploy machinery or build a new cell for landfill, and manage/monitor environmental areas.

And the resolution is so good, site managers can zoom into specific sections of the map to view the situation in more detail.

The resolution of your drone images depends on the quality of the drone's camera and the flight altitude. To find out more, read our in-depth guide to Ground Sample Distance.

As well as viewing the site in a top-down 2D format, site managers can use the data to build 3D models for a dynamic perspective of the job site and conduct valuable measurements and calculations. More of that later.

This sort of information is simply not available using traditional on-the-ground methods - and it can be subsequently shared with team members and stakeholders to improve collaboration and decision-making. 

Repeatable Data

These maps and models a hugely beneficial - and drones can be used to collect this data on a regular basis to provide up-to-date, real-time information.

In contrast, manual surveying can take so long that the situation on the job site has evolved by time the data is anaylsed. The increased costs of ground-based surveying also means it is not prudent to conduct regular surveys.  

Regular drone surveys enable teams to monitor progress, spot for mistakes and aligned with drawings to spot for deviations. These images can be used in CAD overlays, putting original designs on top to spot for any errors and identify if the project is deviating from initial proposals. 

Take this sequence of images, for example, from the Balfour Beatty scheme to construct the A45 Daventry development link road, in Northamptonshire. The pictures show how a drone can be used to monitor and record site progress over the project's lifespan.

Drone imagery reduces guesswork or misinterpretation, which can lead to costly errors. Having such a great visual representation of a site is invaluable for project management and subcontractors.

Michael Lambert, VDC Manager at Chasco Constructors, said: " Combining surveying, drones and CAD information allows us to display our projects in ways never seen before. We provide our team with the big picture and the information they need to more effectively share information and make better-informed decisions.”

Drone Surveying vs Traditional Surveying: Safety

There is no comparison between drone surveying and traditional techniques when it comes to safety.

Traditional methods involve staff manually traversing a site to collect data points, whereas drones can collect this data with staff far away from potentially dangerous areas.

Balfour Beatty drone pilot Wayne Hughes said: “Drones make it safer to gain quantities and stockpile measurements. Drones take people away from places where they could be in harm’s way and it means that we haven’t got people climbing over stockpiles. Instead, the drones can fly over the site and generate a model afterwards, which we can review in the office.”

The same is also true for visual surveys. For example, Quinton Quayle, of Quayle Industries, used a DJI Z30 zoom camera to conduct this roof survey.

The image below shows how the drone was flown above the building and then utilised the Z30 to home in and obtain a crystal-clear image of the chimneys. This process is safe, efficient and effective.

Compare this with traditional surveying methods, which would involve staff working at height using either scaffolding (time consuming to set up, expensive and potentially dangerous) or a cherry picker (expensive).

Drone Surveying vs Traditional Surveying: Data Accuracy 

The efficiency of drones is unrivalled. But this speed counts for little if the accuracy of the data suffers.

Thankfully, drones deliver in this department, too, and they collect highly-accurate data.

For instance, Terra Drone Europe concluded that the P4 RTK could obtain 3cm accuracies without any GCPs, but the accuracy can be enhanced with four of five GCPs. Read the full report.

Meanwhile, test results indicate that, without GCPs, the M300 RTK can achieve a horizontal accuracy of 3cm and a vertical accuracy of 5cm - meeting the requirements of aerial surveying without GCPs. Find out more here.

On the other hand, manual methods can be incredibly accurate. But drones offer that trade off - providing good enough accuracies, while yielding time and cost benefits.

The table below highlights this trade off, showing how a combination of an RTK drone and the laying of some ground points is the optimal solution for accuracy.

Deeper Insights With Drones

Drones enable operators to collect a swathe of data which in turn provides deeper and more wide-ranging insights to drive decision-making and ROI.

For instance, drones can be used to collect photogrammetry and LiDAR data - the second of which is now more accessible thanks to ground-breaking technology such as the DJI L1 sensor - as well as other insights such as thermal and multispectral.

One drone flight produces thousands of measurements, which can be represented in different formats (orthomosaic, point cloud, 3D mesh, DTM, DSM, contour lines, etc). Each pixel of the produced map or point of the 3D model contains 3D geo-data.

For more information on drone surveying data outputs, read our Guide To Drone Mapping.

Combining drone data with processing software enables calculations and measurements to be conducted quickly and easily.

For instance, using DJI Terra, this stockpile can be measured by quickly drawing a boundary around the base - yielding the volume and the cut/fill data. Annotations can also be made.  

Read our Drones For Stockpile Measurements blog for an in-depth guide on this particular process. 

Conducting these quick measurements are all part of the streamlined workflow that drones bring to the table - something which is not possible with ground-based traditional surveying methods.

And as mentioned previously, these insights can be stored and shared quickly, which helps with decision-making and team-wide communication.

Summary: Drones Surveying Vs Traditional Surveying

For years, surveyors have walked their jobsites conducting time-consuming, labour-intensive and potentially dangerous data collection missions.

The emergence of drone technology is making this process a thing of the past, turning data collection into a safe, effective and automated process.

Crucially, the accuracy of the data has not been sacrificed. This, coupled with the rich outputs and information that can be obtained from drones and their associated software, is helping firms realise cost savings and return on investment.

For these reasons, drones should be a key tool in the box on all surveying sites. They don't necessarily have to replace traditional techniques, but they can sure complement them.