Five Ways Drones are Changing the Construction Industryassetdrone.com/adwp/wp-content/uploads/2018/04/5... · System. Drone surveys can cover hundreds or thousands of acres in just

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Five WaysDrones are Changingthe Construction IndustryDrone tools reduce risk and show positive ROI. A white paper for the construction industry by Asset Drone, LLC.

Copyright © 2018 Asset Drone. All rights reserved.

www.assetdrone.com 833-ASSETDRONE

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Table of Contents

Introduction

1. Pre-Construction Survey, Estimating and Planning

2. Construction Monitoring and Inspection by Drone

3. Materials Management Onsite – Stockpile Volumetrics

4. Compliance, Inspection and Regulation

5. Minimizing Risk With a Professional Drone Service

Conclusion

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Introduction Construction projects include multiple risks. Drones are helping to take some of those risks out of the industry. Construction involves risk. The construction site itself is recognized as a dangerous place for worker safety, a place for human accidents and materials damage. It’s also a potential sinkhole for financial assets. Estimates have to be accurate in the beginning and reliable through the project life. Workmanship has to be of sufficient quality,

with contractors often working against a low bid and usually against the clock. The various stages of finished product all have to be approved by inspectors, and the final result has to be acceptable to the owner. Investors throughout all this must live on progress reports.

How can a little, remotely controlled flying device help this situation? We‘ve identified five major areas in this white paper where drones are changing the construction industry. Since 2016, the industry’s adoption of drone services has mushroomed into one of the fastest growing adoption rates. The industry is learning from actual practice that drones can bring efficiencies

and functions not previously possible, helping to minimize risk and deliver a strong ROI. Taking humans out of precarious situations and sending a drone instead makes clear sense for safety and risk-avoidance. But drones do much more than stand-in work. They have cameras and sensors that bring back accurate measurements



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and imagery of all they survey, quickly and affordably. Drones can map topography to allow investors to choose the right land for development. They can validate grade and earthmoving calculations. They can create 3D models of the structure to compare with original plans. And their data can be imported directly into the project team’s computer software, forming part of the compliance record of the project. Drone imagery

also looks good, and comes in digital form to be sent to the construction trailer, or across the world to those information-starved owners and investors. Drones are formally known as Unmanned Aerial Vehicles (UAV), or even more correctly as small Unmanned Aerial Systems (sUAS). Throughout this white paper, we shall refer to them simply as drones.



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One. Pre-Construction Survey, Estimating and Planning The drone’s ability to provide accurate measurements to scale offers fast and affordable custom surveys that help to choose the best site even before the investment begins. These accurate pictures of the ground will continue to be taken as construction work starts, guiding the project.

No construction project begins without money. Funding, rather than earthwork, is the real foundation of any new building. Pre-investment surveying and planning have been quietly revolutionized by the affordability and accuracy of drones and their high-resolution cameras. Using drone services for land surveys means an investor can rapidly examine the entire environment in which a potential project may happen. Drones currently deliver surveys that are accurate to within less than 3 centimeters, using software and methods that align accurately placed control points on the ground with the

known tolerances of GPS, the Global Positioning System. Drone surveys can cover hundreds or thousands of acres in just days rather than weeks. An investor’s viability analysis using drone data can rely on current topographic contour maps, accurate measurements, tree and rock placements, roads and 360-degree aspects of the property. Even 3D modeling is possible by combining multiple fly-by photographs into a composite view, using a process known as photogrammetry. This produces a model drawn



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from real imagery that can be manipulated like any 3D model. Without having to rely purely on numbers, an investor halfway around the world can get a sense of place and a feel for roads, traffic,

community density, and other future developments and how they will impact the value of the current project. Drone imagery is highly marketable, and drone accuracy is actionable, providing a sound basis for decision-making.

The Technology Drone imagery comes from a variety of cameras, mounted by the service company according to the task. Some of the bigger drones can carry up to 20 pounds payload, allowing monster cameras that can produce film-quality footage. And the software that has burgeoned with drone usage also creates a result that is superior to any system before it.



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To understand why this is so, we should know a few jargon words.

• While satellite imagery at best is usually georectified, which means that the images are corrected to match the map overlay they belong to, drone images are usually orthorectified, which means that images are also corrected for the ups and downs of terrain, as well as the curvature of the Earth and the tilt of the camera.

• This results in an image as perfectly to scale across its surface as any map. Orthorectified drone imagery thus gives us a uniform scale, consistently maintained even as images are combined into an orthomosaic map that we can reliably measure from. Being able to take accurate measurements from visual images is a bonus of drone imagery that equates to custom mapping on demand as required.

• None of the data captured in each image is lost, even as images are combined and reconstituted. Even if not displayed, the underlying data or image remains on record, offering numerous spatial coordinates held in point clouds, which form the basic building anchors for 3D modeling.

• Single images are so high-resolution that they can zoom to show details such as serial numbers or bar codes. Drones can fly close to objects, and under and around, and even inside, structures and terrain features. This provides oblique imagery, which an overhead satellite or plane high in the sky can only guess at.

All of this image data is captured in digital form, ready for the project team to make good use of.

Estimating & Planning The digital data supplied by the survey or inspection drone can be imported directly into most construction software platforms such as Autodesk, Bluebeam, Bentley and other BIM and CAD tools that use point-cloud, imagery and shape files. So the drone company is already on the same page as the architects, planners and engineers of the construction project. Drone surveys, models and inspections can complement the existing drawings, planning and design work, and also serve as an affordable

backup set of measurements, derived from the actual project as it happens. Compatibility of data means that projected plans and new data can be aligned to the same reference points, so that any spatial point is the same on all models. This is great cost-saver as calculations made on third-party estimates or old surveys prove different in practice and require new measurements and recalculation instantly, as the project schedule is running.

Site Work Drone cameras move seamlessly from preliminary survey work into site work as the preparation and estimating for earth moving begins. As the construction site is staked and

made ready, some of the ground control points are established that determine the accuracy of drone measurements, and keep the drone’s



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imagery anchored in place consistently through the course of the project. Earth moving is notoriously difficult to estimate in advance, and has to account for many unknowns and unproved assumptions. This early stage of a construction project is regarded as its greatest financial risk, with the ability to throw the entire schedule into danger, along with its asset deployment and funding. The welcome news is that drones are very good at measuring land and materials by length, area and volume. For site work, a drone can cover a site of several acres in just a few hours and supply a point cloud of the entire site. Any other methods would require ground-based, human setup and multiple takes to cover the area and account for terrain changes.

Drones supply accurate and continually updated measurements of earth and materials volumes, to calculate grade and drainage, cut and fill, trenching, paving, concrete, backfill and topsoil - all the vital calculations of creating a successful foundation for the construction project. Drones supply not only estimating data but current observation data as the work progresses, for constant auditing, verification and if necessary recalculation. Bringing the existing site grade to the planned finish grade is most often done by a site-prep subcontractor, and the GC can more easily guarantee this finish - protecting schedule and ROI - by integrating drone survey data into the project.



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Two. Construction Monitoring and Inspection by Drone Drone inspections during construction can show not only current progress for the daily report but also deviations from planning, allowing exact comparisons of as-built with drawings. While safety on the job is enhanced, the risk of error is also reduced, and a record of construction integrity is amassed.

Drones offer an unprecedented ability to monitor the progress of construction projects and compare it with the intended planning. With 3D modeling, high-resolution photography and the ability to take progress photos from the same vantage points throughout the project, drones have unique visualization capabilities.

With drone data ported to the team’s planning platforms, the task of comparing as-built with drawings can happen daily. The construction daily report can show not only what has been done that day, but also flag potential mistakes that can be rectified before much time goes by. This is a key feature of drone inspection during construction.

Inspection With the drone service company integrated into the project team, a regular schedule of inspection

can be performed during the course of the construction project. Flight paths are modified as



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the project progresses and the site changes. Eventually with a high-rise building there’s a framework and interior to inspect as well as exteriors. The drone pilot flies by line-of-sight, watching the drone from outside but also seeing what the drone camera sees. A second person is often also used, operating the camera independently as the pilot controls the drone flight. All personnel are in communication, so as something of interest appears on the screen it’s simple to modify the flight to take a closer look at a feature, or revisit an area, and so on. Using GPS technology, including ground control points ensures that the drone takes a photo from

the same spot every time. Imagery anchored to the same reference points throughout the project means that very exact changes or deviations from the plan can be detected, and measured. A construction project proceeds by checklists, and the drone has its daily or periodic tasks to check off. These can be as detailed as recording the unloading of truckloads of materials, measuring the new stocks, verifying current stocks – piles of aggregate, rock or lumber for example – and logging inventories against building progress. Drones bring real-time management and auditing to the construction site, which means the difference between wasted costs and actual performance.

Safety There are numerous tasks to be performed every day on a construction site, and many of them are dangerous. Wherever a drone can take the place of a human, risk is mitigated. Drones can go where humans cannot easily or safely get to without ladders, ropes or scaffolding. Furthermore, drone inspections are not conducted by workers who may be tired or uninterested; they’re operated by skilled professionals at peak performance. Drones can make the first pass and provide the data that indicates if humans should follow up on specific findings. This enhances the efficient and safe allocation of skilled resources on every project. Safety is a key benefit of using drones in the first place, and safe operation should be the first concern of the drone service. Drones should only fly where there are no workers below, and proximity to cranes and power lines must be safe.

Pre-flight safety and weather checks are the norm for responsible drone pilots and companies, just as they are with passenger aircraft flights. Drone pilots certified by the FAA and covered by drone-specific aviation liability insurance is the minimum standard a general contractor should expect from a drone service company. Drones should reduce liability, not increase it. For the drone inspections, the flight path is made clear of workers, cranes and moving equipment, and the new features of the project are readied for viewing as much as possible. These routine, often daily, inspections can happen at the end of the working day or before it begins, subject to available daylight. Infra-red, LIDAR scanning, and a variety of other sensors are available for specialized inspections also.



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Compliance and Control Photographic prints and digital data from drone inspections can be in the construction trailer within hours, and ready to send to partners and stakeholders, or even to publish and stream through a website. With drone data already ported to team member computers and platforms, the updates build a body of comparison between as-built and original plans. With rapid, actionable data, change-decisions can be made expeditiously by stakeholders anywhere in the world, without wasting time and materials. The stages of construction become documented in dramatically illustrative media that show the past, the current moment and the future, both in 2D and 3D. For permitting and compliance with the numerous jurisdictions that can apply to a

construction project, nothing is more valuable to officials than good documentation. Because data is digital and can be emailed or linked online, inspectors coming to a site can be apprised beforehand of what they’re getting into, and with custom drone missions simple to arrange, any specialized inspections or official areas of concern can be previewed prior to an inspection. Compliance with both regulation and contractual obligation is an important part of every construction project, and one of the five ways that drones are making a huge difference to construction projects. [See our section on Compliance in this white paper.]

Records Drone inspection of a construction project as it progresses builds a library of performance and compliance records that show the project team

and all stakeholders how the plans are working out in reality.



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The ease of drone inspection changes the things we check. The more closely that drone services and construction management work together over time, the more custom and even proprietary innovations and methods develop. The drone’s ability to be sent on custom missions at will encourages new checklists to be created, gathering data for management that was too labor intensive or “finicky” before. It becomes possible to capture photos of every installation and addition, retained digitally for a permanent record of fasteners, couplings, cabling and all such minute details, adding to a vast repository of evidence and measurement regarding the internal development and integrity of a structure. The drone data is never lost, which is important as construction progress covers and encloses

initial structural framework, and hides the installation of systems. Having thousands of high-resolution images time-stamped and to a known scale means managers can revisit an area or an earlier phase, zooming in for close detail, or taking measurements without having to inspect physically or conduct a field trip. If questions arise after project completion – perhaps years later in a lawsuit, for example – evidence captured by drone can constitute a reliable record of diligence for adjudication. The use of drones to capture data during a construction project now results in a vast body of information. This is intellectual property that constitutes a valuable addition to a completed project. Typically the building owner will want property rights to all this data, which can command a price and convey with the building, if sold to a new owner.



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Three. Materials Management Onsite: Stockpile Volumetrics To manage and measure the fluctuating volumes of materials arriving onsite and used in the project, was once a tedious and dangerous job. Drones have changed all that.

We’ve seen how drones can map an area of land and account for elevations and anomalies, producing imagery to scale, not just in 2D but also in 3D. A related task is the specific measurement of piles of materials, generally referred to as stockpile volumetrics. All construction sites have mounds of materials sitting around. Every part of new construction is made from raw and processed materials brought to the site in quantity and moved around, poured, combined or assembled into new infrastructure. The heaps of materials onsite

fluctuate daily as work progresses and as buildings take shape and new materials arrive. Measuring the volume of materials on a construction site, keeping track of depleting inventories, and estimating and ordering the correct quantities all form a vital part of the construction process. We’ve seen how sitework and earth moving call for difficult estimates and measurements of grade, cut and fill, and what to export from or import into the site. And this is just the start of materials management on-site.



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At any time a work zone can have multiple stacks and piles of diverse materials, such as:

• Aggregate materials - gravel, sand, stone, rock, etc.

• Biomass - lumber, logs, mulch, etc.

• Asphalt, cement, open storage bins.

• Debris piles for removal. All of these can be measured through drone data. There are variables of terrain and shape to consider, and skill and experience are needed to get an accurate measurement. It may be necessary to walk the ground around the pile, or to set more ground control points, using high-visibility paint or by anchoring GCP targets. If a drone is already mapping the site, the existing orthomosaic topographical map may be enough to determine the external dimensions of a pile. Perimeter points are selected on the map defining the shape of the pile, and elevation contours are used to make sure they’re on the same plane. Volumetrics calculations take the heights and surface angles of the pile and turn them all into one 3D volume result. Construction thinks in weight rather than volume, so volume is converted to tonnage by including the density of the material in the calculation. This entire measurement pass takes a short time, and it mostly happens in the office – always a safer place than in the field. Previously, piles of materials were measured by human workers clambering over them, usually carrying GPS equipment, and trying not to slide down a

moving pile of sand or a leg-breaking pile of rocks. Stockpile volumetrics used to be like taking any inventory – it was tedious, labor intensive and had to be scheduled, usually at the cost of other work. It was also not always accurate, because humans couldn’t account for the hard-to-reach dips and ledges that drones can see effortlessly. And of course, it was dangerous. The cost of drone-based volumetrics is generally said to be half the cost of the old ground-based method – and this doesn’t account for human damage in accidents. Most accidents stem from simple human trips and stumbles, rather than things blowing up or falling, and industrial terrain is quite treacherous - crossing a landfill on foot, for example, is extremely hazardous. Given the previous manual methods, the ROI of using drones for stockpile measurement is easy for any enterprise to establish, and this has revolutionized materials management around the world. Quarries, mines and other extractors or processors of raw materials are now thinking in terms of continuous monitoring of raw materials levels, from supplier to user. Auditing norms are changing, where inventory is no longer “taken” periodically, but is a continual readout. This new thinking around volumetrics all fits with today’s lean supply chain, where products don’t just sit around wasting space and money, but move to where they’re needed, exactly when they’re needed. The smart supply chain is increasingly feeding a smart construction site, and drones, of course, are part of that smart.



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Four. Compliance, Inspection and Regulation Anticipating the final inspection process long before completion minimizes the risk in final approvals, inspections, and turnover. The advent of drone inspection has made it easier to think in terms of continual monitoring of inventory, performance and quality during construction progress. It has also expanded the ability to share that information. Sharing drone imagery and data with current and future stakeholders in the project - while the project is happening instead of at various finish stages – yields the result of increased stakeholder buy-in, and valuable feedback that allows improvements at a stage when change is still possible. And regulation inspectors of all

jurisdictions appreciate any information that makes their task more transparent. Drones are providing newer and better information than the construction industry has ever had. This is helping to reduce various risks and allowing GCs to set more accurate expectations with the owner. Leveraging the information that drones provide, GCs can help the bottom line and gain a competitive advantage with processes that improve communication with key stakeholders.

Turnover InspectionData sharing during the project works to enhance the relationship between the general contractor and the building owner. Turnover inspection, transitioning from developer control to owner control, is when the owner makes a final inspection before signing off on the project. These inspections are the final confirmation that the GC has done everything and that subcontractor workmanship is of acceptable quality. Owners need to know that their building will operate as they expect, before the GC is long gone and problems have arisen. They use commissioning agents sometimes, to verify before completion that building systems

such as HVAC work properly, and this is a cost they bear because the guarantee of performance is important. As we discussed in Construction Monitoring, the enduring records of construction progress serve as visual evidence of the integrity of the structure and the workmanship. The end of the project is the time when surprises are least welcome, and most damaging. It can be a time when principals of stakeholder firms who have not been seen throughout the project suddenly appear, and have their own ideas of what they expected. Drone imagery and 3D modeling, which is both eye-catching and realistic, serves as a good way to draw out all stakeholders in advance of turnover, possibly pre-empting conflict at completion, and thus, once again through drones, mitigating risk.



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Sharing Information The plus side of increased stakeholder involvement is a better end result. Brasfield & Gorrie, one of the larger construction firms in the nation, demonstrated this recently by giving a virtual-reality walk-through to the staff of a future hospital, very early in its construction. Feedback from staff allowed the firm to make important changes that made a better hospital.

There’s a lot of value in sharing information during construction, but this was always labor-intensive to compile, until drone inspection and monitoring came along to produce real imagery that was easy and affordable. Nowadays, project executives who want to be kept informed can feel less need to visit the site because they’re getting a vivid and realistic picture of progress.

OSHA Inspection While most jurisdictions require inspections of installed or finished stages of development on the construction site, OSHA inspectors are usually dealing with a moving target. OSHA works to maintain worker safety in an environment that keeps changing as the project progresses. This is a great concern, because OSHA recognizes construction as a “high hazard” industry. Working at heights, says OSHA, is a dangerous job and should be avoided wherever possible. OSHA statistics show that falls are the greatest part of construction injuries and deaths. It’s apparent that the very act of using drones in dangerous situations to safeguard workers falls in line with OSHA’s goals. This is true so long as the practice of flying drones is itself done safely – e.g. NOT performed by a worker drafted into flying a DIY mission with a consumer drone, but performed by a safety-conscious professional

service company or an in-house drone division with strict protocols. As with any inspection, from initial permitting to final certificate of occupancy, offing good documentation always helps the process. The advantage of drone images of construction work in progress is especially useful when preparing for an OSHA inspection. The GC risk and safety leaders can study the site for safe setups, mark potential hazards for inspection onsite, and make special requests before an OSHA visit. The construction industry often has sub-contractors who are working within a low bid. But no ROI comes from failing inspections, especially when it comes to worker safety. Once again, sharing information with stakeholders – in this case, inspectors - brings greater buy-in, valuable suggestions, and the ultimate sign-off of approval.

Façade and Exterior Inspection Many cities and states require periodic exterior façade inspections on structures of a certain height, and penalties can be severe for placing the general public in danger from deteriorating finishes and materials.

The inspection checklist for exterior inspections generally looks for water damage, wood decay, peeling trim and sheathing materials, and other indicators that a material is ending its service life or that systems may be failing.



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Enter the drone, once again, to remove the danger of these inspections, or elaborate setups of scaffolding or ladders. Drones can also supply a better set of eyes – including infra-red sensors for

hot and cold spots that may indicate system failure. Compliance is more assured, with resources freed up for actual maintenance, when inspections become routinely easy.



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Five. Using a Professional Drone Service Flying a drone on a construction site demands professional conduct. Anything less will increase liability and hazard.

Should a construction firm fly its own drones, or use a professional drone service? To answer, we need to ask, how should the drone operation be conducted to improve results and also reduce risks? And then ask, can a construction firm do this best itself or by sub-contracting? The advantage of a drone service company is that it specializes in its field, just like other specialized contractors used by the construction firm. Drone usage and development are a substantial discipline. It’s only in recent years that the construction industry has seen the benefits of drones enough to adopt them into use, and while the uptake is now surging, the collaboration is still evolving.

Drones themselves are a frontier industry: highly innovative, still undergoing regulatory evaluation, and still having barely scratched the surface of technological development. It may be too early for even a large construction firm to think about an in-house drone division. Specialized drone companies offer the latest technology that a construction firm may not want to keep up with. We’re also seeing numerous instances of partnerships between drone companies and construction or large-infrastructure companies. Drone companies can leverage or allocate the investment of a drone over many customers and jobs, whereas a



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construction company that only uses a drone periodically may not be able to justify the purchase of the “next version”. The upgrade cycle, similar to other high-tech devices like computers, mobile phones or specialty tools, can prove difficult to justify every few months for a construction company DIY drone department, but a professional drone services company can make these investments as needed, due to economies of scale. Other related examples include the practice of renting or leasing cranes, forklifts or other equipment on a jobsite, so the GC doesn’t have to sink tens of thousands of dollars into underutilized resources.

In many cases, custom software and proprietary methods and systems are being developed through collaborations, with specific ownership and trade-secret agreements in place. Even a large firm developing its own team may want to start by working with a drone company. As discussed previously, drone data on a construction project constitutes a valuable body of intellectual property. Properly organizing, naming, and storing these digital files is an important but tedious process that may not be best done by GC personnel with dozens of other job duties.

Risk A construction site is dangerous enough already, without adding unauthorized or unskillful activities to the existing risks and liability challenges. And while drones increase safety by taking over dangerous tasks in place of humans, drones themselves are hazardous to humans and property unless flown responsibly. Drone services in any construction project should be delivered by professionals and pilots who are FAA-certified, skilled, extremely risk-averse and

heavily insured for drone-specific aviation liability. But this probably won‘t be the case if a construction firm starts a DIY operation using a worker performing drone flights with a consumer drone bought by the company. Although consumer drones may seem easy and cheap for DIY construction inspection, there are numerous pitfalls and potential increased liability. Let’s review some.

Every construction firm should consider legality first and foremost:

• The FAA controls all U.S. airspace. At many locations you cannot fly a drone without FAA’s written approval.

• It’s currently illegal in the U.S. to fly a drone over people’s heads – any construction worker could report this.

Other safety hazards to consider when flying drones onsite include:

• Flying by cranes.

• Flying near power lines – these are notoriously difficult to see.

• Flying outside of line-of-sight or at night – obviously dangerous, and also illegal.

• Losing control of the drone.

• Flying with no regard for weather.

• No pre-flight checks for equipment and conditions.

• Drone operator may already be tired, rather than wide-awake pilot.



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There are other less obvious elements that could also create liabilities and errors:

• No flight path or mission plan - literally “winging it.”

• Directed by a boss with no knowledge of legal and practical constraints.

• Incomplete data surveys, incorrect calculations.

• Worker probably on shift with others, rather than after work with site cleared.

• Probably not compliant with OSHA and other inspection checklists.

• Who is liable for accidents? A lawsuit may come straight at the GC.

• No confidentiality or ownership agreements with intellectual property. Drones should be used to minimize risk on a construction project, not to increase risk. The DIY approach in itself can indicate lack of good risk management. Hazards abound with improper drone usage. And that final note regarding intellectual property should not be overlooked. Intellectual property disputes can arise decades after the circumstances that created the IP.

Best Practices The drone service should be integrated completely into the project management team, coordinating with architects, engineers, client liaison and other services for data compatibility, sharing and publishing, where appropriate. The implications of the new functions now made possible by drones should be absorbed by the whole team, because the way to monitor and plan the construction project is now enlarged, and all team members should be aware of the new possibilities. Checklists can expand to include everything moving into and on the site, with status updates

that trigger the next checks, including revised measurements, calculations, and inspections. This data all adds to the project log with photographic and data evidence, enriching the record of the project for any future questions or against claims regarding workmanship. Done correctly, a full-service drone operation brings skills and capabilities to the construction project that fit synergistically into its risk and liability matrix – as well as its bottom line. Drones should produce a clear, positive ROI and reduce risk.



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Conclusion Hopefully this white paper has illustrated some of the remarkable things that drones can do. The construction industry has now seen the increased safety and high-value data that drone operations can bring to its many tasks, and is increasingly deploying drones in its projects. Drones are not toys but flying cameras that see what humans can miss, and bring back actionable information from their flights. Every best practice is worth taking in order to give the drone a clear and accident-free shot at the target, because the information retrieved can save time, money, hazard and liability. From land surveying to site preparation, through the construction phases and inspection milestones, to completion, turnover and beyond - with a legacy of amazingly detailed records - the

drone is proving its usefulness to the industry and showing how it can help reduce risk. Saving humans from handling many of the necessary or desirable tasks in a construction project yields an obvious return with increased safety. But there are more risks in any construction project than just physical danger. The whole idea of construction carries risk. It’s a speculation that what looks good on paper can be created in reality, and that the project can be built for the estimated cost and will perform as required to deliver the expected return. The general contractor has to bring together a huge array of moving parts to end up with a completed product. Drones can watch over them all.


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Five Ways Drones are Changing the Construction Industryassetdrone.com/adwp/wp-content/uploads/2018/04/5... · System. Drone surveys can cover hundreds or thousands of acres in just