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Drone Surveying: Why it’s Important and How it Works

| 31.10.2022

Drone Surveying: Why it’s Important and How it Works

The earthworks and civil construction industries are growing rapidly. Organizations that have invested in consistent data-gathering and analysis workflows have an advantage over their competition. With greater insights into their worksites, these companies can better plan project logistics, track progress, and catch errors before they turn into costly disputes.  

Topographical surveying with a drone (also known as a “topo”) and a data processing solution like the Propeller Platform provides quick and accessible insight into what’s happening on earthworks sites, taking out the guesswork. Topo-ing with a drone enables site supervisors and superintendents to receive up-to-date maps with accurate measurements quickly (approximately in one day), instead of several days or even weeks. Engineers, managers, and other personnel who split their time between the field and the office can be assured that accurate information is readily available when they arrive on site.

Here, we’ll break down the advantages of surveying with a drone, ways you can accurately measure your site, and what steps to take to build your own drone program to maximize your earthworks business.

Want to jump ahead? Here’s where we’re going.

The Advantages of Site Surveying with a Drone

How Drone Surveying Accurately Measures Earthworks Sites

Steps to Measuring an Earthworks Site with a Drone

What you need to start drone surveying your earthworks site

The Advantages of Site Surveying with a Drone

Technology-enabled workflows, including drone topos, can set your business apart. To be competitive, earthworks professionals need to understand exactly what’s happening on their worksite at any given moment—and how it will impact the final project outcome. Let’s look at the key advantages to drone surveying.

Survey/topo a site before you even begin a job

Site surveying with a drone gives you a rock-solid source of truth about the cubic yardage of material you need to either import or export from the site. Having this information is essential for earthmoving professionals. Conducting your own survey before you move an inch of dirt—or even submit a bid—has several benefits. 

Early drone surveying helps project managers create a realistic budget and timeline. With an accurate assessment of site conditions and the work to be done, project managers can craft an achievable project plan. Just as a framing contractor wouldn’t hammer nails when hanging drywall with eyes closed, drone surveying alleviates the guesswork in earthworks, so you’re ensured of moving dirt with your eyes open. 

With drone surveying and processing platforms like Propeller, you can get an accurate pre-construction survey without spending a large amount of time. It’s simpler than you think. You can fly a prospective job site once and have all the information you need to build an accurate bid to win the business. 

Using drone topography measurements to produce accurate bills of quantities 

Bills of quantities in construction allow for quick and easy comparison of contractor proposals. Since all bidders are quoting the same amount of work, it’s easy to identify differences in price. Bills of quantities are also used to clearly define the scope of work on a project. Since quantities and amounts are provided, there’s no room for misinterpretation and less chance of mathematical errors. Using a drone to survey materials on a prospective jobsite helps ensure that the contractor pricing you submit is accurate, and you’ll be compensated for the work you complete. Comparing your initial site survey to the original ground file provided allows you to request a change-order upfront to secure more money for the project if you spot an unfavorable variance between the two.

Developing change orders to negotiate additional work

The photogrammetric data you get from surveying your site with a drone enables you to execute work with greater accuracy, making change orders less likely. But when the need for change orders does arise, accurate drone data about your site makes it easier to renegotiate potentially problematic changes. When you’re never more than a day or two away from accurate survey data, you can execute more effectively and make better decisions at every project stage to ensure you’re paid accurately. Visual data, such as orthophotos (overhead photos of your site) can make change orders easier, because it’s difficult to argue with a photo!

Resolving disputes

Resolving disputes requires a clear communication and documentation plan. Drone surveys conducted at the start of a project and at regular intervals throughout the course of the work provide a historical record and a consistent (and reliable) record of progress over time. Should a dispute arise, contractors can revisit the relevant site survey to address any concerns.

Accurate records established with drone data also enable contractors to quickly identify and address project errors or concerns and provide clear, accurate, unbiased, and easy-to-understand documentation of every stage in the project.

As we’ve explained, accurate data generated from aerial drone surveys builds efficiencies, promotes safety and sustainability, and enables better project bidding and management when compared to traditional survey methods. Furthermore, providing your customers with direct access, greater accuracy, and projects that finish on time and on budget allow you to maximize your revenue stream and attract new business. 

How Drone Surveying Accurately Measures Earthworks Sites

As technology plays a more central role on earthworks and civil construction sites, meaningful data and accurate site measurement are key to successful projects. Manually counting the number of truckloads of material moved each day can lead to errors, and you could be moving more or less dirt than you thought. 

Better managed projects with drone topos can translate into new business

Accurately tracking your quantities is key to a successful project. Assuming a worksite is more than 10 acres and you’re moving more than 20,000 yards of material, you’ll greatly benefit by surveying your site with a drone. 

Flying your site is significantly faster, more affordable, and just as accurate as traditional, ground-based surveying methods. With frequent topographical surveys from drones, site managers have access to comprehensive, up-to-date measurements. Here are some of the measurements you can calculate using a drone to survey your site. We’ll also share some common mistakes that can lead to inaccurate surveys.

10 measurements a drone can track on construction, mining, and aggregate sites

1. Existing/original ground check (initial topo vs. engineering/survey topo)

2. Progress quantities (survey over survey cut/fill)

3. Current conditions vs. final/finished grade

4. Stockpile quantities

5. Trenching quantities

6. Elevation checks

7. Distances (for projects such as pipe laying)

8. Square footage for concrete laid

9. Verify actual quantities moved vs. truck counts

10. Import and export dirt tracking

When to use drone survey data for as-builts

In the construction industry, “As-Built” refers to a drawing that shows the existing dimensions and conditions of a building, space, or area, as opposed to a design drawing which shows the intended or proposed layout. This is a critical distinction because a constructed site usually does not correspond exactly to the original design drawings.

Depending on the accuracy tolerance (0.1 is the typical tolerance for a jobsite) for an earthworks or civil construction job, surveying with a drone can be a great help. For example, if you need check points from a surveyor to verify accuracy, drone data can provide you with the precise measurements needed for sign off.

A real time surface mapping solution

While many worksites track volumes and progress using drone surveys, often, additional data is needed to understand the reasons behind a project running behind or ahead of schedule that particular day. That data comes from the actual machine movement and progress on the site every day.

While drone surveys capture data from the sky, Propeller’s DirtMate captures data on the ground. Working together, drone surveying and DirtMate give your team easy access to your production data. Mounted on the cab of machines on site and equipped with GPS, DirtMate continuously provides machine location and elevation.

With DirtMate, contractors can track the movements of machines on site, capturing the data needed to develop a full picture of operations on site, every day, on demand. 

Factors leading to inaccurate drone surveys

Here are four workflow mistakes to avoid that contribute to imprecise drone data and some simple tips to avoid them altogether.

1. Poor ground control placement or layout

The most accurate drone surveys include some form of ground control. Even with an RTK-enabled drone, geotagging aerial data alone isn’t sufficient to produce survey-grade accuracy.  Propeller customers, for example, can achieve 1/10ft accuracy by superimposing drone data against locational data collected on the ground using AeroPoints, our “smart” ground control points (GCPs). This is the basis of our PPK workflow that combines two datasets to build a greater level of accuracy. 

GCPs are what keep your data grounded, and if GCPs are not placed correctly, the cumulative errors in a drone’s measured pitch or roll can bring about tens of centimeters of error in a final model. Optimal ground control takes into account topographic variables such as significant elevation change or site size and poor ground control doesn’t.

2. AeroPoint capture time is not long enough

When AeroPoint data is processed, it’s critically important that the time-stamps overlap. If the capture times are erratic and random, it’s much more difficult to process a dataset of your site. At least one AeroPoint should be recording the entire length of a drone survey or for at least 45 minutes. Any less than that and a drone surveyor may run into accuracy problems. 

3. Images with high ISO

ISO is a camera calibration that influences how sensitive your camera is to incoming light. In some cases, a higher ISO works in your favor. Bumping up your ISO in low-light conditions will help your drone images appear brighter without decreasing your shutter speed. However, if you set your ISO above 400, accuracy issues arise when your site data is processed because there’s significantly more “noise” in the source imagery. 

4. Coordinates for the known point are not entered correctly

One way we process AeroPoints data is with the “known point method,” where two types of corrections to the data are processed. One AeroPoint corrects its location to a singular fixed point on earth, and the other AeroPoints correct themselves against the known point. 

Without accurate ground control data, your aerial data will be processed against the wrong points, and from there, you won’t be able to measure the final model with confidence. 

Steps to Measuring an Earthworks Site with a Drone

Surveying your earthworks or civil construction site with a drone offers many efficiencies to your workflow. With a drone, you can conduct topographic surveys that rival the quality of highly accurate measurements collected by traditional base and rover methods, but in a fraction of the time. This provides you with substantial cost savings for your site survey needs and reduces labor time in the field. Here’s an outline of the steps involved in the drone surveying process

Flying your site

The first question you may ask is “do I need a survey background or degree in order to survey my worksite with a drone?” The short answer is “no.” However you’ll first need to obtain your FAA license to fly an unmanned aerial vehicle (UAV), known as a Part 107 license.

Passing your FAA Part 107 test and earning your remote pilot certificate as a commercial drone pilot might seem like a difficult or time-consuming process, especially without experience. In fact, it’s much simpler than most people think. To help, we created a comprehensive study guide with everything you need to pass the Part 107 remote pilot test on your first try.

Once you are certified as a commercial drone pilot, you are allowed to operate your drone in Class G airspace, unless you have a permit to fly in controlled airspace and can fly within 400 feet (122 meters) above or beside a building or structure, even if the tallest part of that building or structure is higher than 400 feet. The key to flying in these restricted areas is to get permission from the FAA, otherwise you risk a fine or losing your remote pilot certificate. You also must keep your UAV within visual line-of-sight at all times.

With your license in hand and some practice, you’ll now be ready to plan your mission and capture aerial images of your job site by flying your drone. But what happens next with the data you’ve collected? It must be processed correctly in order to build accurate maps of your site.

Watch our First Flight video below and learn about registering your drone, what to do in the office before your flight, what to do on-site, and how to conduct your first flight.

PPK Processing

PPK (post-processing kinematic) technology, as used by the Propeller Platform, is a highly accurate solution for most worksites, from quarries to large-scale earthworks projects. In a PPK workflow, a drone equipped with RTK hardware records GPS files, along with base station data generated by Propeller’s AeroPoints, attaches geocoordinates to the images collected during flight. The result is a faster, simpler, and more reliable survey, with data accurate to 1/10 of one foot. 

Furthermore, with an optimized workflow, drone survey teams don’t need to fly the entire worksite in a single mission — they only need to fly the areas where work has been done. Composite surveys allow subsections or adjacent regions to be merged with other surveys.

Combatting misperceptions

Misperceptions do persist about the reliability of surveying with a drone. Here, we address a few of them:

Measurements are not accurate with drone surveys: Site contractors are paid based on the amount of dirt moved, and historically those numbers have not been calculated, but estimated based on the truck count and the average amount in a truckload. Drone survey data is a game changer because it captures accurate cut volumes quickly based on millions of data points. Customers are assured of more accurate billing and costly disputes are avoided.

It’s too expensive: You may think that you need an expensive drone, someone that is highly trained, special survey equipment or a costly web service contract to process data. However, it’s simple to add an affordable drone to help you collect topographic data. And with the right processing platform like Propeller, you’re able to obtain the data you need from each drone flight and ensure you get compensated for the work you complete, thereby realizing a significant return on your investment in a drone program.

It’s complicated: Contractors may feel that surveying a worksite with a drone is really difficult, but it’s actually not. You plan your mission, fly your site, upload your data for processing and then analyze the results, which you can share across your team.

What you need to start drone surveying your earthworks site

Within earthworks there are many tasks that factor into ensuring a project is well managed and completed on time. These include precise project schedules, timely data sharing, accurate surveying, and keeping track of material movement onsite. Previously, earthwork surveys would require someone to walk the entire site to perform duties like measuring cut and fills and stockpiles, which could be a very slow and time-consuming process. However, using drones for topographic surveys can significantly reduce time spent in the field and provide data that can be uploaded and analyzed quickly to make timely decisions. 

You may be wondering how difficult it is to start a drone surveying program, asking questions like: what equipment do I need?, what’s the best drone for my company?, etc. In this section we’ll walk you through the three main components that make up the drone surveying process; choosing a drone, utilizing ground control points (GCPs), and processing your survey data.

How to pick the right drone

When choosing the right drone for your site, there are a few key areas to consider to ensure you’re getting the best fit for your needs. Propeller understands these and has made it easy for you to learn about drones suitable for surveying in the earthworks industry in our Recommended Drones section. Here, you can review drones compatible with the Propeller Platform where we’ve outlined some of the key features for each drone along with other considerations when choosing the right one to fit your business needs. These include affordability, site coverage, ease of use, fixed wing or quadcopter craft, and weather conditions you may encounter when flying.  Below are drones compatible with the Propeller Platform.

Ground control

Site surveying with a drone means you will need some other equipment in order to maximize your survey data. For example, drone pilots set up GCPs, such as Propeller’s AeroPoints, that are positioned strategically around a construction or earthworks site. These provide a geographical position of your site that can be matched with the drone photogrammetry data and used to provide an accurate map of your survey area. 

This video below explains what is ground control, why it’s important, best practices for ground control placement, and uploading data to the Propeller Platform.

Supporting software

Site surveying with a drone doesn’t end with just the drone flight. You’ll need a software platform to process your aerial data. Processing this drone data through Propeller’s PPK solution allows you to perform further measurements and provide deeper project insights to your stakeholders. Output files like cut/fill reports, stockpile reports and cross section measurements are just a few of the options our platform offers you. 

Once you have activated your drone, learned about ground control and coordinate reference systems, planned and flown your first mission, and set up your site, this video explains how upload data to the Propeller data processing portal.

The accurate site data you can capture by surveying with a drone will enable you to execute more effectively and make better decisions at every stage of your projects.

Want to learn more about how you can use drones to accurately survey your worksites and streamline your earthworks business operations? Request a demo with us today.

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