Feature: Surveying At Speed
An engineering and surveying firm takes the plunge with a mobile mapping system and finds it pays dividends, especially on transportation projects.
An engineering and surveying firm takes the plunge with a mobile mapping system and finds it pays dividends, especially on transportation projects.
We have seen the future, and in the surveying world, it comes in the form of mobile scanning. In fact, you could call it a revolution! What is it? Mobile scanning combines 3D laser scanning, GPS, inertial measurement, and video technologies. The equipment can be mounted on a variety of vehicles such as SUVs, vans, trucks, sedans, RTV utility vehicles, vessels, and rail trucks.
This technology offers many benefits. It is less expensive than traditional surveying technologies. Data collection is much faster because massive amounts of data can be collected while traveling at posted speeds. With fewer personnel working beside busy roadways, mobile scanning creates safer job sites. It does not impede traffic flow. And the dense data collected lends itself to future
data extraction without additional field visits.
We believe mobile scanning is changing the entire landscape of surveying. Instead of numerous crews in the field transmitting data to a few office personnel who process it, a single survey mobile scanning crew can collect tremendous amounts of data in a fraction of the time. An entire team of surveyors in the office, who process the data, compile the CAD deliverables, and create models and simulations supports that crew.
McKim & Creed first invested in 3D laser scanning technology in 2006 when we purchased our first time-of-flight, or pulse, system. We use it for planimetric and control mapping, high-accident areas along highways, bridge substructures, utility substations, and volumetric scans.
In July 2009, we expanded our 3D laser scanning capabilities to include phase-based scanning. This technology has proven most effective for energy facilities, processing plants, manufacturing facilities, amusement and theme parks, civil engineering projects, and architectural/MEP
applications.
But we first became acquainted with mobile scanning in the summer of 2008. It was nearly love at first sight, but we wanted to get to know the technology before we made a lifelong commitment. The “old school” comes out in us when it comes to trusting new technology. We needed to perform various tests and quality control checks and compare lots of data before we trusted this technology.
One test we performed was on the accuracy and reliability of mobile scanning. Working with equipment provider
Terrapoint, based in The Woodlands, Texas, we scanned a three-mile area of highway using static scanning, re-scanned the same area using mobile scanning, and compared the results. With static scanning, two crews worked for one week to collect the data, while with mobile scanning, the data was collected in less than half a day. The DTM (digital terrain model) data collected using mobile scanning was within less than 0.10 feet, with an average accuracy of less than 0.05 feet. This spurred us to present this amazing technology to
NCDOT (North Carolina Department of Transportation), hoping to convince them that mobile scanning is the safest, fastest, and most cost-effective method of collecting and mapping DTM and planimetric data for transportation projects.
Trying a New Technology
NCDOT needed design-grade pavement DTMs for design to widen five sections of interstate highway. The sections to be surveyed were located along divided highways with high-traffic volumes. Typically, NCDOT uses a combination of helicopter mapping and aerial photography to gather DTM data. This requires that surveyors work along heavily traveled roadsides to place survey controls on the ground, creating safety issues. Helicopter photogrammetry can also be costly and time consuming.
McKim & Creed offered mobile scanning as an alternative method to capture the topographic and planimetric data NCDOT needed. The agency had never used his technology.
We shared the results of our test scan, and based on those results, NCDOT agreed to implement mobile scanning technology on one project. This was conducted along U.S. 74/76/17 between Leland and Wilmington, North Carolina, and our purpose was to designate pavement limits and other features. Working with Terrapoint, we collected mobile scans for the entire project site, then supplemented those scans with static scans every mile as a quality-control measure. Survey data showing edges of pavement, travelways, and curb/gutter features was extracted from point clouds generated by the laser scanners. The data was then processed in the office, mapped, and delivered to NCDOT in CAD format.
NCDOT was satisfied with the results and authorized McKim & Creed and Terrapoint to complete four additional mobile scanning projects for sections of highway throughout the state. Deliverables for each assignment included:
- MicroStation 3-D DTM design files
- MicroStation TIN files
- MicroStation 2-D planimetric design files
- Geopak files, including all extracted linework
- QA/QC TIN-to-TIN comparison design files
- QA/QC comparison spreadsheets
- Complete scan database
- Video and .jpeg files of the entire data collection
Then NCDOT asked if the McKim & Creed/Terrapoint team could mobile scan railroads. The answer: “Absolutely!” Data from three sections of railroad encompassing approximately 33 miles of railway needed to be collected, so the McKim & Creed/Terrapoint team retrofitted the mobile scanning vehicle to NCDOT’s high-rail truck. The truck traveled all the project areas in at least one direction and most in both directions to ensure full scanning coverage. The team completed the field data collection for all three projects within two days, scanning approximately 18 miles of rail per day and providing accurate rail surveys with maximum safety and minimal disruption of rail service.
NCDOT is pleased with the cost, safety, efficiency, and quality of the data and is investigating the potential use of mobile scanning technology for future projects. In November 2009, McKim & Creed was awarded the top honor for engineering excellence, the 2010 Henry A. Stikes Grand Conceptor Award, from the
American Council of Engineering Companies of North Carolina for these mobile scanning projects.
Launching MoDaC
While we completed our first projects using the Terrapoint technology, we did more research and ultimately decided to invest in the
Optech Lynx Mobile Mapper system. This is the heart and soul of McKim & Creed’s MoDaC (Mobile Data Collection) system, which we launched in fall 2009. The orientation of the scanners, along with the incredible speed (200 kHz) per scanner head, allows our system to collect survey-grade data at over 400,000 points per second while traveling at roadway speed, thereby increasing our ability to provide base mapping information in the most efficient manner. An on-board passive imaging system enables surveyors to check the data as it is being collected. The MoDaC system is also easy to retrofit onto various modes of transportation.
At first we saw only the numerous opportunities within the highway and railroad industries to use mobile scanning. Now that we’ve launched MoDaC, we see limitless possibilities in a variety of industries. We see applications for beach erosion monitoring, within the racing industry, and even in the film industry. Mobile scanning has great applications for GIS asset management and can work hand-in-hand with subsurface utility engineers to quickly locate underground utilities. The scanned point clouds, with the aid of digital imagery, enable us to map the reflective paints used for marking underground utilities. This allows our virtual surveyors in the office to map the lines accurately without having to collect the data with conventional survey methods.
Of course, MoDaC won’t work for every surveying application. You can’t drive through a dense forest or inside a steam plant to collect data. But even though it probably won’t replace all our conventional collection technologies, we believe mobile scanning represents a significant shift in the industry and, in many areas, represents the wave of the future.
As with any emerging technology, we are learning more each day. We have performed numerous mobile scans throughout the southeastern United States since launching our MoDaC system. The clarity of the point cloud data is amazing, and the accuracies have all been within design survey tolerances.
Working with our clients, we are looking at the compatibility of the entire data set within existing design software. Engineers and designers are concerned about the size of the files and the learning curve of using the data, and it appears major software companies are developing their software to accommodate the data. With all this going on and the success of mobile mapping, welcome to the future!
Tim Van Gelder, PLS is a regional manager with McKim & Creed, an engineering, surveying, and GIS firm headquartered in Wilmington, North Carolina.
Marty Stoughton, PLS serves as the firm’s director of business development for mobile scanning services. For more information about mobile scanning, visit www.mckimcreed.com or contact Marty Stoughton.
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Rules of the Game: Surveying Family Burial Grounds
In Texas and elsewhere
When people think of cemeteries, most think of the formal lands set aside in every civilized place in the world. Images of headstones, iron fences, and mausoleums come to mind. However, there also exist informal cemeteries. They are created prescriptively by the act of burying a deceased person there, and they have no formal declaration or evidence of their existence recorded at a courthouse or other depository of legal records.
Many such informal cemeteries exist throughout rural areas, and Texas is no exception. Often they are overgrown, forgotten, and left in a state of disuse for decades. They are also often hard to find even if their existence is known, because they were originally established in a remote and little-used part of the property.
The Law
The law in Texas recognizes the existence of such cemeteries and gives them legal status. Vernon’s Texas Codes Annotated, Health and Safety, 5, Sections 534.000 to 750 (TSA 5 § 534 to 750) states:
§ 711.010 Unknown or Abandoned Cemetery
(a) The owner of property on which an unknown cemetery is discovered or on which an abandoned cemetery is located may not construct improvements on the property in a manner that would further disturb the cemetery until the human remains interred in the cemetery are removed under a written order issued by the state registrar or the state registrar’s designee under Section 711.004(f)
(b) On petition of the owner of the property, a district court of the county in which an unknown cemetery is discovered or an abandoned cemetery is located shall order the removal of any dedication for cemetery purposes that affects the property. If all human remains on the property have not previously been removed, the court shall order the removal of the human remains from the cemetery to a perpetual care cemetery. A petition under this subsection shall be made ex parte in the name of the owner of the property without naming any defendant or joinder of any other person. (Added by Acts 1999, 76th Leg., ch. 703 § 1, eff. June 18, 1999)
§ 711.011 Filing Record of Unknown Cemetery
(a) A person who discovers an unknown or abandoned cemetery shall file notice of the cemetery with the county clerk of the county in which the cemetery is located. The notice must contain a legal description of the land on which the unknown or abandoned cemetery was found and describe the approximate location of the cemetery and the evidence of the cemetery that was discovered.
(b) A county clerk may not charge a fee for filing notice under this section (Added by Acts 1999, 76th Leg., ch. 703 § 1, eff. June 18, 1999)
The Surveyor’s Report
It is in the filing of the record of an unknown cemetery that the land surveyors can play an important part. Often with old cemeteries the question arises about whose property the cemetery is on. The land surveyor can research the land records to find the legal description of the property and can make necessary measurements to determine where on the property the cemetery is located.
Texas doesn’t have a known specific legal form for filing a record of an unknown cemetery. Instead it is done in an affidavit format.
According to the law above, there are essentially three general items of information that the document requires:
- the legal description of the property,
- the approximate location, and
- the evidence that was discovered.
The law does not state anything more specific, so the person reporting has to use his or her creativity in creating the report.
The legal description can be a reference to one of two things: a volume and page (file number) reference to a recorded plat, or a recorded metes and bounds description. An actual copy of the recorded plat or metes and bounds can also be used.
The approximate location can be either a written description or a sketch showing the location of the cemetery. If an actual copy of the recorded plat is used for the legal description, the location can be marked directly on it.
The evidence can be photographs; a sketch of the location of graves, tombstones, and fences; or a copy of the inscriptions upon the tombstones. It may be possible to obtain a list of persons buried there from a local source: a property owner, a relative of the deceased, an undertaker, or someone connected with the cemetery. It is always useful to have this list included in the report because it makes a permanent record for interested persons in the future.
This affidavit does not have to be notarized by a public notary, although it does not hurt to have it notarized: notarization gives the document an aura of legality. These cemetery reports would then show up on a title report informing potential purchasers of the cemetery’s existence.
A surveyor can take the report to a higher degree of detail and sophistication. If the cemetery does not have a formal recorded description of its boundaries (and many don’t), the registered professional land surveyor can establish those boundary lines and set the corners of the cemetery. He can then tie the newly set corners into the boundary of the property on which the cemetery sits and produce a drawing or metes and bounds description of the cemeteries boundaries. This survey can then be recorded as the legal description and location portions of the report (
Figure 1).
This portion of the report would be governed by the standards of the Professional Land Surveying Practices Act and the General Rules of Procedures and Practices adopted by the
Texas Board of Professional Land Surveying, the same as any boundary survey in Texas (or per your state’s adoption).
Determining Boundaries
It is difficult to determine the boundaries of an old cemetery due to its age and unkempt state. There are often numerous unmarked graves, and if any fences still exist it is possible there are unmarked graves outside the area.
Searching for unmarked graves generally involves looking for depressions in the ground. A funeral plate (a metal marker used by undertakers to mark a grave) may sometimes be found to indicate a grave’s existence if a headstone was not set. Ground penetrating radar can locate graves, but it is costly and is of limited effectiveness in certain soil types and high water tables. Probing for coffins at potential gravesites is unappealing and time consuming, but the method is commonly used. Often roses or other plants planted at the grave indicate their existence.
There are basically three methods of determining the boundaries of a cemetery with an undefined boundary. The first is parole evidence. Local people who have visited the cemetery in the past may remember its original extents and be able to indicate where they are. The second is for the surveyor to make a judgment based upon the overall evidence found at the site, taking into account the location of fences, tombstones, unmarked graves, and vegetation. The third method is to use a practice identified by the American military by the acronym S.W.A.G. (simple wild-ass guess). The surveyor should make an effort to limit the cemetery size to minimize its encumbrance on the overall property.
A surveyor can also take the evidence portion of the report to a higher degree of detail and sophistication. He or she can prepare a formal site plan or planimetric map of the cemetery. (In Texas this plan would fall under category nine, an Investigative Survey of the Texas Society of Professional Surveyors Manual of Practice.) This plan can show all the available evidence of the cemetery’s existence and its location on the site. It can show not only cemetery features but other physical features, such as trees, grade breaks, and water bodies, all of which would act as a reference for any future visit. As part of the investigative survey tombstone inscriptions can be listed and, if possible, photographs included. This planimetric map can be recorded as the evidence part of the report (
Figure 2).
In states other than Texas certainly there are laws regarding similar burial grounds. Some of the ideas expressed above could be applied there also, and it would be reasonable and probably lawful for land surveyors to record cemetery reports at their own local courthouses.
Graveyard Preservation
Various individuals and organizations are interested in preserving small family plots. Some are interested because they have ancestors buried there, while others because they have a sense of heritage and would like to see remnants of the past preserved for posterity. Examples of government organizations in Texas interested in graveyard preservation are the
Texas Historical Commission,
Save Texas Cemeteries, and the Texas Historical Cemetery Guardianship Association.
Thousands of unrecorded cemeteries are estimated to be in Texas alone. Surveying these could be a possible source of income for land surveyors (it is a niche market). Unfortunately, most individuals and organizations interested in cemetery preservation are volunteer and non-profit, so they do not have the funds to hire surveyors. These organizations would need to get grants from charitable foundations to afford to have cemeteries properly surveyed. If surveyors were to volunteer their time and expertise to survey these burial grounds, their compensation would be an enhancement to their public image. Surveying cemeteries for reports could be a public service project for state surveying societies.
The Texas Historical Commission offers programs involving the preservation of cemeteries. From 2001 until 2005 they had the R.I.P. program: Record, Investigate, and Protect, whose purpose was to expand the existing
Texas Historic Sites Atlas by including historic cemeteries (the atlas is a database of approximately 238,000 sites documenting Texas history). They also run the R.I.P. guardian program, whereby local groups can adopt an historic Texas cemetery or a cemetery that qualifies as an eligible property under the criteria for designation. The organization then coordinates maintenance and preservation programs for the adopted site.
[The
Historic Texas Cemetery Designation Program was developed to address the problem of destruction and illegal removal of historic cemeteries. This designation cannot guarantee that a cemetery will not be destroyed, but official recognition of these community landmarks highlights their importance and promotes an attitude of respect for them.
To receive a designation as a historic Texas cemetery, the cemetery must meet two basic criteria: it must be a least 50 years old, and it must be worthy of preservation for its historic associations. An application form for a Historic Texas Cemetery designation is available from the Texas Historic Commission. The application has there attachments that are required: 1) a narrative history that relates its historical significance; 2) documentation for the Affidavit of Dedication for Cemetery Purposes (the best documentation is a survey done by a professional surveyor; this would be the same boundary and topographic survey information as described above); and 3) photographs of the important features of the cemetery.]
Terrance Mish received a Bachelor of Science Degree in Surveying from Ferris State College in 1981. He is a licensed land surveyor in Virginia and Texas.
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Editor's Desk: Mobile Mapping Emerges
By Tom Gibson
In a recent issue of
Pangaea, our e-newsletter,
Jeff Salmon talked about stimulus funds forthcoming from Washington that will be applied to developing a smart electrical grid for the country. The idea is to minimize blackouts, increase the efficiency and reliability of transporting and distributing electricity, increase power quality to handle the increasing number of electronic devices being used, and allow for integrating renewable energy sources such as wind and solar. In essence, it applies the internet to the grid to make it less centrally controlled and more interactive with consumers. As new power lines are built and the system otherwise needs positioning and measuring, surveyors and other geomatics professionals enter the picture.
Closely related to the smart grid and following a parallel path, an article in
Geomatics World magazine says one of the primary causes of blackouts is electrical arcing caused by trees that grow or fall too close to transmission lines. Flying helicopters, some aerial mapping companies are implementing lidar to map power line corridors and pinpoint infringements on lines by tree growth.
I mention this because this issue focuses on laser scanning, and one thing that became apparent to us while developing it was the emergence of mobile mapping. This technology started with aerial applications, but now it’s seeing increased use on our roads. It typically involves mounting a laser scanner on the roof of a motor vehicle and driving along as you measure the roadway and its surroundings. Mobile mapping provides a much faster way of gathering data and keeps surveyors out of traffic and harm’s way. In the process, it should give surveyors another source of work, especially as software improves to handle the huge amounts of data generated and convert them to deliverables.
Winter Olympics
Changing the subject, I hope all of you will watch the
Winter Olympics coming up this month from British Columbia, Canada. Personally, I have two reasons to watch. Many of the events take place at
Whistler Blackcomb, a renowned ski resort I’ve visited twice. I have a special place in my heart for Whistler, as I’ve found it one of the most terrific ski areas with the nicest, most pedestrian-friendly ski village you’ll find. Once you park your car, you can walk from your condo to either of the two huge ski mountains, along with a host of restaurants and shops. To give you an idea how big the place is, Blackcomb has a one-mile vertical rise!
Of course, the tremendous expanse of venues, facilities, and infrastructure required for an Olympics took a huge surveying and construction effort over the course of several years. We explore the surveying part of it in our cover story this month. I’d like to think that TV viewers will ooh and aah at the events and say “wow, look at the surveying somebody did to build that ski jump,” but few probably will. At least I’ll have the double satisfaction of knowing I’ve skied the mountains that will be shown on TV and I know about the surveying that went into building top-notch facilities that draw the best athletes from around the world.
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Feature: Let The Games Begin
With steep mountains and exacting standards, surveying for the 2010 Olympic and Paralympic Winter Games venues in Whistler, British Columbia proved no ordinary job.
On July 2, 2003, when Brian Brown heard the news that his hometown of Whistler, British Columbia had won the 2010 Olympic and Paralympic Winter Games bid, there was more than one reason to celebrate. A passionate skier, the land surveyor hadn’t missed a season at local ski resort Whistler/Blackcomb in nearly 50 years. He couldn’t think of a better place in the world to hold the
2010 Games.
Brown also knew a great deal of surveying work would need to be done for the numerous new venues, including the Nordic ski tracks and ski jump at Whistler Olympic Park, a sliding center, and an athletes’ village. “To say that it would be a lot of work is quite the understatement,” laughs Brown. “It was going to be a Herculean task. It wasn’t just the venues required, there was also all the infrastructure to support the events—new roads and bridges, pedestrian access to the competition sites, a new lift, and even a new sewage treatment plant.”
Brown knew that the Vancouver Organizing Committee for the 2010 Olympic and Paralympic Winter Games, or VANOC, had to start work from scratch on constructing almost every venue except the downhill sites, which are located in an existing ski area (even those required realignment work for environmental impact mitigation and to improve their safety features). VANOC would also have to get the work done on challenging terrain and in equally challenging circumstances.
Whistler, located in the heart of British Columbia’s Coast Mountain Range, is a world-renowned ski area for good reason, where skiers enjoy steep slopes and long runs on Whistler and Blackcomb Mountains at both low and high altitude. Only an hour-and-a-half’s drive from Vancouver, the area also has spectacular scenery, boasting thickly-forested hills liberally endowed with tumbling mountain creeks and waterfalls.
Getting surveying and construction equipment in and out of the sites would prove no simple task. Working in dense bush and on slopes steep enough for Olympic competition wouldn’t be easy either. On top of everything else, winter is a long season at Whistler, constraining construction activity as a result of both weather and intense visitor activity. The 10,000-strong town quadruples in size during peak ski season, and accommodation for large crews becomes difficult to arrange.
Brown was up for the challenge, but he knew he couldn’t do it alone. He immediately called Jim Christie, manager of engineering surveys for
McElhanney Consulting Services in Vancouver. “We had worked together many times before in the Whistler area,” says Brown. “I knew we’d make a good team for the bid.” Christie, also a land surveyor, agrees. “McElhanney definitely wanted to get involved.”
Celebrating its centenary in 2010, McElhanney Consulting and its sister company McElhanney Land Surveying comprise a surveying, mapping, and engineering partnership with more than 800 staff members in branch offices throughout western Canada. When Brown called Christie to see if he would be interested, McElhanney Consulting was about to undertake extensive surveying work for improvements to the
Sea-to-Sky Highway, the main access route to Whistler from Vancouver. Christie jumped on board immediately.
“We thought that combining Brian’s local knowledge and connections with our extensive resources and experience would be ideal,” he recalls. “McElhanney has also been sponsoring two Canadian athletes, Nordic skier Sara Renner and alpine skier and Paralympian Matt Hallat, so this felt like another good fit for us. Besides,” adds Christie, “it just looked like good fun.”
Start with the Bidding
Before the fun, however, came the bidding process. Starting in 2003, VANOC issued requests-for-proposals for each phase of construction of every venue, including the necessary surveying components. “I knew accuracy was going to be an important component of the bids—the venues have to meet Olympic qualifying measurements and have to be ‘homologated.’ That’s a new word we learned along the way!” says Christie. Homologaters, as it turns out, are the people who check and certify the official specifications of every venue for consistency with other sporting venues on the international circuit, so record-breaking results can be measured accurately and fairly against previous records set elsewhere in the world. Getting measurements absolutely accurate was therefore essential.
But VANOC also simply didn’t have time for mistakes or repetition. With short windows of opportunity for construction and an ambitious schedule to have the venues built in time for the competition, both VANOC and the Whistler 2020 Corporation, which owns the Athletes’ Village, wanted detailed surveys of the venues completed in fast timelines.
“They couldn’t do the Athletes’ Village like a typical development project, for example,” says Christie. “They wanted all the detailed survey information up front, because they were under such huge time pressure for completion. They needed to be able to make design decisions as they went along, with all the information at hand, because they knew they wouldn’t have time to go back and do more surveys.” The pressure was on for the Brown and McElhanney team to get everything right first time.
The partners planned carefully to ensure they could meet the challenge, but that was easier said than done in some cases. They had only ten weeks from start to finish to do detailed topographical surveys, drawings, and quality control checks and deliver final plans for the Athletes’ Village site, for example. The area covered 263 acres of rough, irregular terrain, dense with trees and heavy underbrush and populated by numerous resident black bears, which posed a constant hazard to unwary crews. “That was very challenging,” states Christie. “Winter was coming—we ended up finishing the job in snow. Basically, 300 crew days had to be squeezed into 7 weeks, including weekends, so we could get it done in time. We used as many as ten crews between us.”
Tying the survey into control that had been done for the Sea-to-Sky Highway, the crews used total stations and conventional methods for most of that part of the project, using GPS where possible around the clearer edges of the site. Brown and Christie delivered digital plans to their client on time. “Another reason Whistler 2020 Corporation picked us for that job,” adds Christie, “is that they liked the environmentally friendly option of using different survey methodologies and equipment to minimize cutting lines through the trees, as well as providing digital plans rather than paper, and we were happy to accommodate that.”
While providing topography for the Nordic ski trails and locating their route with GPS was relatively straightforward by comparison, other venues offered scenarios as challenging as that of the Athletes’ Village. Christie and Brown also had crews on the ski jump venue, including the ramp and the landing area. “It was an extremely steep slope,” says Brown. “Just to stand straight you needed one leg longer than the other! And it was physically challenging moving constantly up and down the slope. We were also dealing with a construction site, of course, so it was hard to keep a clear line of sight. Wherever we went on site we continually had to adapt to the terrain and obstacles in the way.”
The survey crews also had to set control far more often than would be required on flat terrain. “There were no simple traverses on this project,” Brown explains. The control network repeatedly had to be changed due to the high level of construction activity and the requirement to preserve trees next to the venue to shade it from the warmth of the midday sun.
“And of course, the steeper the ground, the greater the combination of distance and angles, the more room for error,” says Christie. “We used a combination of precise conventional equipment consisting of a
Leica DNA 03 level with invar rods and a Leica TCA 2003 total station with precise tribrachs for setting the control and conducting the quality control checks during the construction of the facility,” he adds. On top of everything else, the location for the ski jump was moved twice before it was finalized, to improve access and visibility.
Sled Track Has Its Challenges
Similar challenges were involved with the track at the Whistler Sliding Centre, used for bobsleigh, skeleton, and luge races. Brown and Christie kept two crews busy much of the time on topographical surveys of the slope, construction control, and quality control of the 1,715-meter (5,626-foot) track. Again using Leica TCA 2003 total stations, Brown and Christie focused on individual spots on a mocked-up fully-finished version of the track to ensure the grade was within a tolerance of three millimeters (less than 1/8 of an inch) of specifications.
“The track can’t go out of grade,” explains Christie, “for the simple reason that you can’t have sleighs bouncing out of it!” A flatness survey had to be done to make sure there were no gaps or imperfections on the concrete. “They basically use a flat pipe, moving it up and down the surface of the track to see if it hits any air pockets. The teams practice in the summer on wheels,” he adds, “so any bumps in the concrete could be a huge safety issue.”
Bumps might not be the only safety issue for the Olympic teams, however. Brown recalls, chuckling, the first runs down the finished sliding track. “They got a call at the top saying there was a black bear hanging over the edge watching the sleighs go by,” he recalls. “Good thing he wasn’t fast enough to catch himself an athlete, though!” Neither Brown nor Christie have been down the track themselves, but not because they are worried about bears. “No thanks!” exclaims Christie. “Just walking down the slope next to it was adventure enough,” agrees Brown, although he says he is tempted to have a go with one of the professionals if he ever gets a chance.
It has been a long but rewarding experience for both men, who have devoted several years to the Winter Games project. Brown began work as early as fall 2003 on a photo survey for the ski jump site and was still finalizing legal surveys for the Athletes’ Village in December 2009. In addition to all the Whistler venues, including the Nordic ski trails, Whistler Media Centre, and Medals Plaza, between their two companies they also worked on the snowboarding venue at Cypress Mountain in West Vancouver and the curling venues and opening/closing ceremony venue at B.C. Place in Vancouver.
In the meantime, both men have tickets to events at the Winter Games. Brown is looking forward to the mens’ bobsleigh, the men’s and women’s alpine giant slaloms, and the women’s downhill, and Christie managed to score tickets to the men’s gold-medal hockey game and closing ceremonies. “It’s going to be great watching the athletes in the finished venues,” says Christie. “It feels like a huge accomplishment that is going to mean a great deal to a lot of people all over the world.”
Brown concurs. “I’ve skied those slopes at Whistler so many times over the years,” he reminisces. “With all the improvements, Whistler/Blackcomb is rated among the top three downhill courses in the world. Being involved in the survey work has given that an extra dimension I am really going to enjoy every time I’m out there.”
Katherine Gordon is a freelance writer and author based in Gabriola Island, British Columbia, Canada. Her award-winning history of land surveying in British Columbia, Made to Measure, was published by Sono Nis Press in 2006.
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3D Scanning: High-Definition Mobile Mapping
As professional surveyors, we all recognize the need to stay abreast of the latest developments in technology to provide our clients with timely and affordable solutions. Technology innovation is a key component to the success of our profession. Mobile mapping (or mobile laser scanning) is a relatively new technology that only a handful of surveying firms in the United States have adopted. These firms have identified the great potential for mobile mapping as it expands surveying’s tool box.
Overview
Mobile mapping is a non-invasive, state-of-the-art solution that incorporates the most advanced ground-based lidar sensors, cameras, and an inertial measuring unit to collect survey-quality point data quickly and accurately. General applications include asset inventory mapping; corridor project work, including roadway and rail transportation, pipelines, and overhead utilities; tunnel mapping; construction management for design-build; FAA airport design and layout plans; harbor and shoreline mapping; and streetscape design.
Because mobile laser scanning is so new, we have yet to identify all application possibilities. As clients become increasingly comfortable with the concept and see the benefits of mobile mapping, they begin to understand how it can be used in their workflows.
To point out the elephant in the room, some of our fellow colleagues are concerned that mobile laser scanning will do more harm than good for their businesses by replacing conventional survey methods. However, if you take a closer look at the technology and its potential applications, the integration of mobile mapping can complement existing methods such as conventional surveying, GPS, photogrammetry, airborne lidar, and HDS laser scanning.
The efficiency you can gain by using mobile mapping must not be overlooked when bidding topographic surveys along lengthy transportation and utility corridors. Just as GPS did not entirely replace the total station, the use of mobile mapping methods certainly will not replace more conventional methods of topographic data collection. It is now second nature for surveyors to decide when GPS will be more efficient than a total station in measuring a given length. In much the same way, length of route will be a major factor in deciding whether a surveyor should consider mobile mapping methods of data capture. To refuse consideration of this technology will put a surveyor at a decided disadvantage.
However, mobile mapping may not be the most appropriate tool for every project. As a line-of-sight tool, if you can’t see it, you can’t capture it, and in certain cases it must be supplemented by more conventional data-collection methods.
Overall, mobile laser scanning is not just providing a better picture for our clients but a more complete picture of the intended project.
Project Applications
Mobile laser scanning offers numerous advantages over airborne mapping and conventional ground surveys, if it’s the right tool for the project. Mobile mapping can provide efficient acquisition of millions of 3D design points per minute, and with a data density from 0.01 foot point spacing (depending on system settings for the project), it allows for faster data acquisition compared to other survey methods.
For rail and transportation projects, mobile laser scanning provides increased safety for project personnel and the general public because data can be collected remotely, day or night, removing the need for traffic diversion caused by construction and maintenance activities.
Overall, mobile laser scanning provides designers with a more complete picture of the project, with very dense, highly accurate point measurements and the ability to locate features that are cost-prohibitive or logistically difficult to capture with other methodologies.
Railroad Corridor Project: Mobile mapping technology gives surveyors the ability to collect up to 400,000 points per second, compared to one point every few seconds with traditional survey methods. SAM, Inc. recently completed mobile mapping and digital photo acquisition and processing for a 32-mile commuter and freight railroad corridor. The route was driven in both directions to ensure complete coverage, with additional passes on sidings. The total length of the data acquisition was 64 miles and was completed in one day.
The mobile lidar data was controlled by continuous operating reference stations (CORS) and survey ground control points. For a specific section of the route, ground control target points were painted on the railroad ties and located with GPS.
One of the key benefits to mobile laser scanning is that it allows for one mobilization with multiple returns on investment. This can mean significant savings for design firms or government agencies who are keeping a keen eye on project budgets. By using this advanced mapping technology for the railroad corridor project, SAM, Inc. was able to gather all required data point measurements in one setting and go back to “mine” the data at a later date for other applications. For this project, SAM, Inc. gathered data for high-accuracy planimetric and topographic mapping, classified point-cloud data, railroad centerline files, and asset-inventory-type feature datasets.
Erosion Analysis Project: SAM, Inc. captured two
miles of a four-lane roadway in only four hours. Data acquisition included six total passes to capture median and ditches, drive lanes, shoulders, and adjoining ditches that were “driven” using the
LYNX Mobile Mapping System. The project was controlled using several CORS, and the lidar was processed to produce detailed topographic map data for use in evaluating the rate of erosion at the site. Mapping was provided in MicroStation DGN format.
Transportation Mapping Accuracy Assessment: This project included the mapping of three miles of rural two-lane roadway previously conventionally surveyed and mapped by
SAM, Inc. Mobile lidar was collected for the purpose of comparing the accuracy and comprehensiveness of the mapping products produced by each method. The data was processed using three methods of survey control to determine the achievable accuracies using each of the three methods: CORS only, four SAM Inc. local survey ground control points, and the use of local survey control with photo-identifiable ground points. Data accuracy comparisons were completed using triangulation software.
Challenges
While we recognize the many benefits of mobile laser scanning, we also know it comes with as many challenges. All early adopters of this technology are to some extent blazing a trail. Most surveyors can probably agree that there is not a clear road map to all of the potential uses of this technology, which, in my opinion, may not necessarily be a negative, but a unique opportunity for early adopters of mobile mapping to scope out this road map.
Internal
Data management: One of the biggest strengths of mobile mapping is its ability to capture dense data sets, but this also presents one of its biggest challenges. Data sets gathered by mobile mapping are very large and require extensive network storage space and network and workstation processing capabilities. The advent of airborne lidar technology faced similar challenges.
Upfront investment: The capital investment cost of the hardware and software and the IT requirements of mobile mapping can be afforded (at this point) only by larger surveying and mapping firms. An easy solution is to consider the cost of ownership versus the cost of partnering with a firm that already owns the mobile mapping technology.
Staff education and developing: So far the pool of candidates with experience is very limited. Surveyors must also invest in educating their own staff to develop experts on mobile mapping so as to bring every project to a successful and profitable conclusion.
External
Client education and industry adoption: Change can be hard, and the adoption of mobile mapping into our profession is no different. Early adopters must prove to clients that this technology is not going to add risk or jeopardize the outcome of the projects. Continued client education will be a significant contributor to its successful adoption.
Lack of standards and best practices: Standards and best practices, such as control and accuracy standards, are still in development. Similar to the early days of airborne lidar, the companies who are operating these systems will develop their own processes and standards. As time goes by, the community of users will come together and determine industry standards for mobile laser scanning and its various applications.
Mobile laser scanning is in some ways a bridge between surveying and aerial mapping methodologies. It can be used to collect a very wide range of data sets at various accuracies, from GIS grade to survey grade. It has required us to draw on our collective experience as surveyors, photogrammetrists, and engineers. Project design, data processing methods, deliverable development, client education, etc. will require input and expertise from multiple disciplines within the profession.
We have only begun to understand the uses and benefits of mobile mapping. This innovative technology will in no way completely replace existing solutions and methods, but rather provides surveying and mapping firms with another solution for specific project challenges that we all face. Ultimately, it allows us to position ourselves and our profession as progressive and forward-thinking.
Gordon Perry, RPLS, PLS is senior project manager for Surveying And Mapping (SAM Inc.), the largest surveying and mapping firm in Texas. Gordon is responsible for managing advanced technologies such as GPS, HDS laser scanning, and mobile laser scanning in SAM, Inc.’s Austin office.
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