PHOTOGRAMMETRY - Photomodeler
FEBRUARY 2016PHOTOGRAMMETRY Elevation CertificateComplex BIM ProjectSoftware & FieldworkThe latest from FEMARequires mix of techPays off for students
PHOTOGRAMMETRYHelps Surveyors Save Timeand Improve AccuracyAerial view of a debris slide catchment area. This photo shows the catchment area beforethe contractor has removed the debris and is one of many that will be imported intoPhotoModeler to calculate the total debris volume of the slide.Surveying is a time and labor intensive process thatrequires extremely high levels of accuracy. Two NorthAmerican surveyors are addressing this challengeby using photogrammetry to increase the numberof points surveyed by several orders of magnitudewhile reducing field time by half or more. Photogrammetry is theprocess of generating measurements and models from photographs.“Photogrammetry helps us win more jobs by providing more competitive pricing,” said Paul Lepine, Senior Geotechnical Technicianfor exp Services Inc., Burnaby, British Columbia. “Photogrammetryprovides much more accurate measurements since every point iscreated in 3 or 4 photos and these photos are reconciled together toobtain closure for the entire model,” said Eric Blackburn, Presidentof EBI Surveying, Tampa, Florida.» JERRY FIREMANRock slope surveysexp specializes in performing rock slope surveys that are requiredwhen rock slope remediation systems are built alongside highways.The company surveys the rock slopes and calculates the amountof mesh required to cover the slope and also proposed locationsfor metal stanchions used to secure the mesh. The company alsoestimates the required rock scaling—the removal of loose rock fromslopes—and shotcrete—concrete that is sprayed onto the rock slopes.One of the critical areas in the survey is at the joint planes formedby breaks of natural origin in the continuity of either a layer or bodyof rock. Water often invades cracks at the joint line or fracture. Lateras the temperature drops and freezes the water, its volume expands.This expansion pushes the rocks on either side of the joint apart,breaking off pieces of rock that may fall onto the road.Displayed with permission The American Surveyor February 2016 Copyright 2016 Cheves Media www.Amerisurv.com
Below: 3D point cloud (right) of the debris slide seen inprevious image. This point cloud, used to determine thetotal volume of the debris, was created in PhotoModelerfrom about 90 individual photos of the slide. SmartMatchpoints can be seen dotting the actual site images on the left.View of catchment areaof slide after contractor’sremoval of the debris.In the past, exp surveyors used a total station to survey a fewthousand points on a typical 100 meter long rock slope. This processnormally took three days. One of their challenges was that thetwo-lane highways are typically only 15 meters wide and the rockslope cuts are commonly 30 to 50 meters high and sometimes up to100 meters. “It is very difficult to take measurements that high andto find safe and appropriate total station setups while surveying bythe highway,” Lepine said.Several years ago, exp began using PhotoModeler photogrammetry software from Eos Systems. exp originally used a differentsoftware package but switched to PhotoModeler when it wasdiscovered that PhotoModeler couldbe purchased for the amount that it costto rent the other software for one month.When Lepine first began using photogrammetry,he placed photo control targets on the rock andsurveyed the 3D coordinates for those points in orderto provide the proper scale rotation and translation for thephotographs. He then walked along the rock slope and tookpictures with a digital camera, taking care to obtain at least a 60%overlap between adjacent pictures. This process took only one dayfor a 100 meter long rock slope.Displayed with permission The American Surveyor February 2016 Copyright 2016 Cheves Media www.Amerisurv.com
Photo of a bluff requiring rock slope remediation. Part of a government remediation project,this photo will be one of many used to calculate the mesh area and other requirements.When Lepine returns to the office, heuploads the photos into the photogrammetry software and uses a feature calledSmartMatch to automatically detect andmatch features across multiple overlappingphotos. The software then computes theposition of each point in the images in 3Dspace. “SmartMatch saves a considerableamount of time compared to the previousprocess of manually matching commonfeatures between the photos,” Lepine said.“The time required to orient the photos isreduced from a few days to a few hours. Theresult is a dense point cloud consisting ofmillions of points that defines the topography of the rock slope to a much higher levelof accuracy than was possible in the past.”Accurately depicting the 3D geometry ofthe rock slope is critical because contractorsprepare their bids for the remediation workbased on this geometry.More recently, exp has further improvedthe survey process by using a DJI S900Hexacopter drone with a Calibrated SonyNX5T camera to take the photos. LepineRendered 3D surface model (right) of the bluff in previous image. Theindividual photos taken at the site are shown in the two images onthe left. PhotoModeler surface drawing tools were used to outlinethe area of proposed slope mesh (green lines on surface model).The surface model with 3D lines outlining proposed slope meshareas are imported into AutoCAD Civil 3D to calculate meshsurface areas and produce final drawings.Displayed with permission The American Surveyor February 2016 Copyright 2016 Cheves Media www.Amerisurv.com
Survey of bank site. Anchor points set uparound the survey site will later be usedby the software to determine the correctposition and angle for each shot.commands the drone to hover and movesthe gimbal into position for the shot of therock slope. This method allows for bettersurvey coverage of the rock slope thanphotos previously taken along the highwayby hand. As with the manual photos, heoverlaps each photo with the preceding shot.Exp’s governmental customers typicallymarkup photos of the rock slope with linesdrawn to indicate the outline of where theywant the mesh. Lepine then makes a 3Dmodel of the mesh using the surface drawingtools in PhotoModeler. At this point, themodel is exported to AutoCAD Civil 3Dwhere Lepine calculates the area of eachsection of mesh, creates annotations andgenerates separate surface models of eachmesh. These deliverables are then providedto exp’s client.Sometimes the client requestsmodifications and when the client issatisfied Lepine produces a final drawingthat is included in the package providedto the contractors for bidding. Often,when the construction is being performed,contractors may propose changes, suchas extending the mesh to cover additionalareas of the rock slope. In this situation, expreturns to the site after the constructionis completed and performs an as-builtsurvey using PhotoModeler that is used todetermine the contractor’s payment.Bank site in PhotoModeler. On the right is the set of georeferenced 3D point locations whichwill be exported to AutoCAD software. Two of the 40 images taken of the survey site can beseen on the left.Redevelopment surveysEBI Surveying based in Tampa, Florida isanother company that has moved fromconventional surveying to photogrammetry. The company focuses on surveyingproperties prior to redevelopment. Itproduces a map of the site that shows eachof the improvements, such as buildings,pavement, signs, fences and inlets, as wellas the topography of the site. In the pastEBI measured each individual feature witha total station which took between two andthree days for a typical one acre commercialsite. The accuracy that could be achieved bythis approach was limited by the fact thateach measurement was independent of theothers so the dilution of precision could notbe calculated.“After making the decision to givephotogrammetry a try, I took a look atseveral different software packages andfound they were bulky and difficult touse,” said Eric Blackburn, President of EBI.“But when I tried PhotoModeler I foundthat its developers had taken a lot of timeto develop an interface that makes senseto the user. The program works and feelsa lot like Microsoft Office or AutoCAD soit’s easy to understand. One of my favoritefeatures is the 3D viewer which I keep openwhile I am marking and referencing thephotos so I can easily keep track of whichareas have been completed and which onesstill require work.”Blackburn now begins the survey processby setting anchor points around the site thatwill later be used by the software to determine the correct position and angle for eachshot. He then sets up a camera on a 50 foothigh telescoping pixie pole and takes 40 to100 photos of each site, indexing the camerafield of view about 15 feet for each shot toDisplayed with permission The American Surveyor February 2016 Copyright 2016 Cheves Media www.Amerisurv.com
achieve 60% or greater overlap betweenshots. There are still some improvementsthat can’t be measured with photographsbecause key dimensions are hidden fromview. For example, Blackburn must openmanhole covers and take a measurementto the bottom of the pipe. However, in totaleliminating the need to measure every pointmanually has reduced the field time requiredfor a property from 15 to 20 hours in the pastto only 6 to 8 hours today.Blackburn brings the camera data backto the office and loads the photos into thephotogrammetry software. He opens upphotos and manually selects an anchor.The software then automatically finds eachadditional occurrence of that anchor point inother photos so Blackburn only needs to openup one photo for each anchor point. “I actually requested that this feature be added tothe software,” Blackburn said. “In fact, I havemade several requests for improvementsto the software and have often seen thosechanges reflected in subsequent programupdates.” Once Blackburn has marked andreferenced the photos, the software generatesa set of georeferenced 3D point locationswhich are then exported to AutoCADsoftware. This is delivered to the customer.“Photogrammetry offers major advantages both in time savings and qualityimprovements,” Blackburn concluded.“We find that we spend 60% to 70% lesstime in the field because we no longerhave to measure most individual points.Another advantage is that weno longer have to worry aboutthe possibility of missing animprovement that should beincluded on the survey. In thepast when this happened Ineeded to go back to the site totake additional measurements.Now that we take photos of theentire site the client can easilymeasure the position of anyimprovements based on the 3D model.Photogrammetry also provides much moreaccurate measurements and calculatesthe potential error for every point whichis from 1 to 3 hundredths of a foot. I ameagerly awaiting the time when regulationspermit the use of drones for surveyingbecause the ability to take higher photoswill improve the quality of surveys.” Jerry Fireman is the President of StructuredInformation (www.strucinfo.com) and has spentmore than 30 years writing about nearly everytype of technology. To date, he has written morethan 10,000 articles that have been published inover 3,000 trade journals, technical journalsand mass media around the world.This resulting map was created usingPhotomodeler. An entire second set of datawas acquired using conventional methodsas a comparison. On average, a differenceof less than 0.1’ was observed betweenthe elevations of asphalt and concreteestablished by Photomodelerand the conventional data.Intersection in PhotoModeler. Blackburn said, “In creating the line work andpoints for the topographic survey, I experimented with creating surfaces tobetter reflect field conditions. While this graphic is not used for the design, itis a powerful example of the capabilities of this software. Any portion of thesurface shown can be used to create three dimensional points and lineworkaccurate to less than 0.1’ both vertically and horizontally.”Displayed with permission The American Surveyor February 2016 Copyright 2016 Cheves Media www.Amerisurv.com
PHOTOGRAMMETRY Rock slope surveys exp specializes in performing rock slope surveys that are required when rock slope remediation systems are built alongside highways. The company surveys the rock slopes and calculates the amount of mesh required to cover the slope and also proposed locations for metal stanchions used to secure the mesh.
Digitizing the outline of a large 2D template is difficult to do efficiently, accurately, and cost-effectively. There are a few tools for doing this but an interesting new option is to use a camera and photogrammetry software. PhotoModeler is the long-standing leader of desktop photogrammetry software and is a reasonable price.
Photogrammetry is a cost efficient surveying method for mapping large areas. Photogrammetry may be safer than other surveying methods. It is safer to take photographs of a dangerous area than to place surveyors in harms way. Photogrammetry provides the ability to map areas inaccessible to field crews.
photogrammetry. He developed the analytical solutions to space resection, orientation, intersection, rectification, and control extension using direction cosines. Church, a professor at Syracuse University and one of the founding members of the American Society of Photogrammetry, is referred to as the "American Father of Photogrammetry".
Photogrammetry has been previously validated as an effective technology for documenting both damaged vehicles and scenes [1,2,3,4,5,6,7,8,9,10,11,12]. Modern photogrammetry uses the same photogrammetric principles, but requires less user input and delivers more data points in its solution. Photogrammetry software is capable
Unity Photogrammetry Workflow 3 1. Overview 1.1. Introduction What is photogrammetry? Photogrammetry is the process of authoring a digital asset using multiple photos of the original real-
White light scanner (point clouds) Photogrammetry solutions. 18 22/08/2017 Photogrammetry solutions Photogrammetry (Single points, Adapter, Features) . White-Light Scanner (Structured light) Very high accuracy (down to some µm) Highest resolution Scalable for different volumes (mm to several m)
photogrammetry in my view is one of your first steps to learning cad and modeling. a good pathwa y to more complex concepts. digitally store and easily find your patterns vs. physical patt erns that consume much space and can be unruly to organize or get lost.
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