Landair Surveying News

Scanning For Forensic Criminal Defense Presentations

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Winning Cases by Using Cutting Edge Digital Scanning Equipment: Taking Animation and Jury Presentations to a New Level

3D Laser Scanning is a rapidly growing technology sweeping across the nation.  While the technology is relatively new, it is now being embraced by law enforcement agencies, federal crime agencies, the secret service and major police departments all over the world.  This technology gives the crime team and defense team ways to capture and show crime scene information that was not available until a few years ago.   The technology literally allows either team, the prosecution or the defense, the ability to bring a scene into the courtroom so that everyone can view it.  It has been praised by Georgia trial judges. Just this month the Georgia Bureau of Investigation has begun using a 3D Laser Scanner.

Laser Scanner Data in Court

“To my knowledge no laser scanner data properly presented has ever been ruled inadmissible in any court in the United States.  In fact many police departments and federal agencies use scanners to collect evidence for all types of criminal and civil investigations. It is the best way available to collect data.  The data is so graphic and intuitive that it is very easy to see the results and make logical judgments and precise measurements.”  (Forensic expert)

(See Appendix A for Court and Forensic Case Examples)

It has even made its way into the media forefront in shows like Crime 360 and CSI.  This technology is here to stay.  It is accepted and has become the benchmark for clear and concise presentation of very complex crime scenes.

How does the technology work?

Broad Specifications

  • 50,000 Data Points Collected per second.
  • Range 300 yards
  • 360 Degree Color Photography
  • Able to  produce ¼ inch accuracy
  • Fly through Videos
  • Extremely effective at capturing the scene

Leica C 10 3D Laser Scanner

The technology was invented about 15 years ago to map very precise structures like oil refineries.  Originally it could only be used by trained scientists.  However, in about 2000 the technology became much more user friendly, and by 2005, with the addition of an onboard color camera and compact platform, it quickly became state of the art.  Now in 2011 it is becoming a very effective working tool for capturing existing conditions in any environment.  Now it is use in thousands of different types of data capture task all over the world.

How does it operate? You turn the scanner on and it captures a 360 degree spherical photograph of the area. When the photographic collection is complete the scanner fires a laser at a rate of 50,000 times per second at an effective distance of 150 yards in all directions of the sphere. The laser beam travels out, hits an object and returns the position and elevation of the object and that is one point. The results of collecting millions of these points builds a 3D image that looks like a “hologram” and is called a point cloud. The points are registered to the color photography and are painted with the same color as the pixels in the digital photography and so the points collected  are colored and measurable to an accuracy of about ¼ of an inch. All the data is graphic and represents  the most precise way that you can capture data.  We have been using this technology at LandAir Surveying for the last 7 years which has allowed us to become very proficient with the many tools it provides.

What tools does it give you that you do not have?

  • You have 360 degree photographs of the scene, and you can walk a jury down the road or inside a house and let them look at everything in every room in color from any view.
  • You can overlay the scan data over the photographic data and make precise measurements between any two points real time while testifying.
  • You can place a virtual camera anywhere within the 3D scan data and view the scene from infinite points of view.
  • You can build a fly through video and take the jury down the road at any speed you choose.  For Example, you can show the scene in slow motion and then speed up the camera to actual speed showing a car traveling at 40mph per hour, thus demonstrating what the driver saw and viewed at that speed. You can then show the same scene in slow motion so a jury can study the details.
  • Inside a house you can show a room or scene from any view and show the jury what a homeowner would see looking out of their window and what a person outside would see looking in from the street, and everything would be geometrically perfect.
  • The information collected can be used to build a re-creation of an accident or crime and can show your version of how the crime or accident most likely occurred.

All of this is done with photography and scanned points that are registered together and which are scientifically calibrated and precise.  These tools are very powerful communication tools and judges like them because they save the jury trips to the site.  Police departments all over America are now starting to use this method to document their crime scenes and present their evidence of a crime.  They are able to use the information collected to show line of site details and what perpetrators and victims saw from different points of view.  If new evidence comes up a year later they can make new measurements from the original data.

How much does it cost?

Most jobs consist of field data collection and a good scanning group should be able to get 8 to 10 set ups per day with a long range scanner which includes the 360 degree spherical photographs. The data is then processed and a video for the client is made.  For example driving down the center of the road at some speed, and the ability to view and manipulate the photographs on the provided FREE software call “TrueView”.

This basic package can cost from $3500 for a relatively small site and of course the cost goes up as the size and the complexity of the project increases.  This is sufficient to take into court.  Smaller jobs may include scanning four ways down a busy intersection.  Anyone can use the software provided to run the Windows Media files and open and view the 360 degree photos. In complicated cases we also can build accident recreation videos showing the accident as we believe it happened based on the facts this takes more time and cost more.

When the bus accident occurred on I 75 and Northside Drive in Atlanta the scene was scanned to collect data.  When the bridge collapsed in Minneapolis the scene was scanned.  When Princess Diana died in a car accident in a tunnel in Europe that became to most scanned accident scene in the world.

There are many more uses of the data depending on what a legal team needs in order to show their version of the incident.  For example, we can create multiple views of the same situation to show what somebody may or may not have been able to view of an incident based on where they were standing. We can create camera views at eye level in a car or at eye level of a bystander standing next to a pole.  We can insert realistic car models into a video and show the view from the windshield looking out.  We can show the same car as viewed from the top of an overpass as it drives under the overpass.  All this comes from the original data collection.

What steps are necessary to use the information and make a presentation in court?  Below are the actual preparation and steps for one of our recent court cases.

This case involved working with a criminal defense team to help defend Joe Client.  He was charged with vehicular homicide and the case had been moving through the system for 5 years.

Step 1. We met with the defendant and all the defense attorneys and walked the site to determine what was important to them.  We discussed all the facts and looked at what little evidence remained at the scene.  We listened to our client tell his version of the incident. Our task was to clearly document the site to show the court.
Step 2. We reviewed the photographs that were 5 years old and begin to study the evidence. We were provided police reports, photographs and other pertinent information regarding the case.
Step 3. We discussed with the defense attorney the area to be scanned for the presentation.
Step 4. We collected the scan data and 360 degree photographs of the site.  This took about a 2 days.
Step 5. With our processed data and photographs we met with the defense team and presented several site videos of the travel of the car as it had been described.  We determined that we would produce one video example in slow motion for detailed study of the scene and a second at real time speed.
Step 6. We began to build sequence boards that would be the basis for the design work of the accident re-creation video presentation.  We used the photographs, the evidence, the police reports and the scan data to build the information needed.
Step 7. We produced our first animation in black in white and delivered it to the defense team for their input.  The team was very impressed and enthusiastic and immediately started giving us input and making great suggestions.
Step 8. We produced a second version and then a final version of the re-creation that we would present in court.  We were convinced that we had made the re-creation as close as possible to the police reports and to our client’s account of the accident.
Step 9. We presented the final version to a mock jury.  They are obviously taken with the realism of the animation and immediately understood what took place .  They voted for acquittal.  We used their input to make a final adjustments to the video recreation.
Step 10. We went to court and were prepared to show the court how the technology works, show the digital video fly through, the 360 photos showing the accident scene and finally the accident re-creation.  During pretrial motions we were told to go in the empty jury room where we presented all our information to the prosecutor with the defense team and we were question at length by the prosecutor as to the technology and the data collection process.  The case was  settled on a plea later.

Conclusion

3D Laser Surveying is now starting to become a forceful forensic technology that can be used to bring data to court cases that was not available even 5 years ago.  This is the most advanced way to collect crime scene and civil accident data and has been used in many courts across the country.  This method is currently being used in all types of civil and criminal litigation including civil cases and insurance case where a catastrophic even or arson has taken place to bring the scene to the courtroom and show them scientifically, graphically and intuitively what the environment in which a civil or criminal incident looked like, and it allows for permanent 3D archival of the area involved.

H. Tate Jones Ga. RLS
Contact information tjones@lasurveying.com
1875 Old Alabama Road Suite 1120 Roswell, Ga
770 730 9950

Appendix A

Court and Forensic References

(Norcross, Ga., 03 September 2009)  District Attorney Joe Mulholland of the South Georgia Judicial Circuit added yet another legal case reference to the growing number of U.S. court cases in which Leica Geosystems 3D laser scan data has been admitted into evidence when he successfully proffered and tendered to the jury a visually compelling Leica TruView.

During the murder trial of Antonio Jerome Greenlee in Decatur County Superior Court, witness and crime scene investigator, Andy Forte of the Thomas County Sheriff’s Department, used Leica TruView to virtually place the jury at the crime scene and to show them how the homicide could have occurred.  The case stems from the homicide of 21-year-old Ebony Clarke of Bainbridge, GA, who was shot and killed on August 12th, 2008, during a street altercation between two men.

Leica TruView is a free, web-enabled panoramic point cloud viewer that allows users to view, pan, zoom, measure and markup the incredibly rich point cloud captured by the Leica ScanStation 3D laser scanner.  The Leica ScanStation allows investigators to first photograph and then make millions of measurements of a crime scene in just a few minutes thus “freezing the scene in time” forever.  A Leica TruView data set can then be generated in minutes after scanning for briefings or analysis or as in this case as a jury exhibit.

“The jury really, really liked it and we had jurors comment afterwards about how effective it was” said District Attorney Mulholland.  “We not only used the TruView to support Andy’s testimony, but the judge then allowed Andy to show it again during my direct examination of other witnesses as I asked them questions about where they were standing or where the shooter was.  TruView is basically a high-tech picture.  It is not testimony.  It is offered as an exhibit and demonstrative evidence.  This seemed to play well with the judge.  The Defense did not object and I think that they thought the same thing.”

Mulholland went on to say that after the trial the judge called him to the bench and commented on how effective the use of the Leica TruView was and encouraged him to use it again.  “We certainly plan on doing so.  The scanning software was absolutely fantastic” said the D.A. The judge also contacted Thomas County Sheriff R. Carlton Powell to thank him for his agency’s assistance with the case and to compliment him on the professional nature of the exhibits generated by his investigators.   Sheriff Powell was instrumental in bringing ScanStation technology to Georgia law enforcement and has made it available to the Georgia Bureau of Investigation and other agencies as a courtesy.

  • California DOJ Invests in 3-D Crime-Scene Laser Scanners to Support Forensic Crime Scene InvestigationAfter seeing first-hand how the Leica Geosystems ScanStation 2 can be deployed to quickly measure and model extensive indoor and outdoor mass casualty mock crime scenes, the California Department of Justice’s Bureau of Forensic Services (BFS) moved quickly to purchase two Leica ScanStation 2 high speed, high definition 3D laser scanning systems from Leica Geosystems.
  • Pennsylvania State Police Response to Amish School Shooting
  • The Amish School shooting occurred on the morning of Monday, October 2, 2006 when a gunman took hostages and eventually killed five girls (aged 7–13) and then killed himself at West Nickel Mines School. The Pennsylvania State Police used a Leica laser scanner at the scene for forensic mapping.
  • Albuquerque Police Chief Ray Schultz discusses the reasons his department acquired a Leica ScanStation for crime scene investigation.
  • This BBC news clip shows British Police Investigators in the Paris tunnel where Princess Diana died using a Leica 3D laser scanner.
  • 3D Scanning: Laser Scanning the I-35W Bridge Collapse
    Professional Surveyor Magazine – March 2008
    Bruce Jenkins
    Much has been made of the role aerial mappers and surveyors have played in victim rescue and bridge reconstruction after the August 1, 2007 collapse of the I-35W bridge in Minneapolis. But what about laser scanning? This is the story of how the Minnesota Department of Transportation deployed 3D laser scanning to capture a detailed forensic record of the bridge collapse and help with the ensuing investigation.

Taking a Chance with Laser Scanning Technology

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LandAir Surveying began doing business in the 1988 by offering site and topographic surveys to the engineering and construction industry. The company originally started with two survey crews. There were fewer than ten employees and surveying services were offered in Georgia and nearby states. Over the next ten years the business expanded tremendously to include cell tower site surveying services to telecommunications providers. Three-thousand or more cell tower sites were surveyed with conventional survey methods. In 2002 there was a shift of focus to transportation engineering projects and in 2005 we got a project to survey the I-20 Bridge over a large river near Atlanta, Georgia. It was this shift that transformed the technology used and overall business direction of LandAir Surveying. Problems arose with the traditional surveying methods. The size and length of the bridge made it difficult for a survey team to get an accurate survey with the traditional survey equipment. Our owner sought alternative solutions and in the process determined that 3D laser scanning could be used to achieve more reliable results for the bridge survey.

Adjusting to 3D Laser Scanning

LandAir Surveying purchased their first laser scanning equipment in 2005 after viewing demonstrations and since then have expanded into newer and more specific and advanced models. The scanners were used in conjunction with more traditional surveying methods. Work flow methods were refined as experience grew with the new technology. With this increased experience came calls for exterior, interior, and structural surveys of various buildings and environments. 3D laser scanning made it possible to easily scan a building and produce drawings and 3D data sets based on the scan. Time required to produce an accurate survey was reduced with the help of this technology. Enhanced scanning allows surveying of building areas that are not easily accessible without the technology. Larger jobs such as wide spread manufacturing facilities have more accurate site surveys with complete 3D imaging and laser scanning is becoming more of a standard in these  environments. These types of surveys would not be possible with traditional surveying methods. Data processing had to be refined to better handle bigger data sets created by laser scanning. New scanning innovations have created safer work environments for surveying crews and new business opportunities.

3D laser scanning is quite different from other surveying methods. With this technology, field notes do not exist. Instead, surveyors strictly deal with data points and image files. A typical 3D laser survey project work flow is to set up the equipment and seek a line of sight for each point. Scanning devices use technology that floods a area with precise data points at rates of up to 300,000 points per second. After a scan is complete, the information can be viewed, verified, and referenced whenever necessary. Files are large in size and have to have the right computer power and resources for proper management. Machines with vast amounts of RAM and enhanced graphic cards make critical post-processing more reliable. These computers must be capable of supporting vital processes such as proper data workflow, storage, retrieval, and backups. While the service is advantageous, we found that more effort is required to find clients who can benefit from the technology. Initially clients could see the benefits, but not all could afford the service. However as the technology grew and became more efficient and the benefits became more reliably more companies are using this technology as a way of surveying existing conditions.  Having been in the 3d Laser Scanning business for 7 years our firm has become an industry leader in this emerging technology.

What can you do with a 3d Laser Scanner

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What can you do with a 3d Laser Scanner that you cannot do with other types of surveying and mapping equipment?

Scanner on 5” standard Tri Pod

Scanner on 5” standard Tri Pod

First let’s look back at where the 3D Laser Scanner came from.  Some people call it a Laser Scanner; Aerial mappers call it tripod scanning. I think it is more widely known as terrestrial scanning.  So laser scanning as I am talking about is all done on a tripod that is anywhere from 5’ tall to 15’ tall.  Most are moved around either on wheels attached to the tripod or by hand or now we even have truck mounts to improve speed.  As I said in my first article the uses’ for this technology are as varied as the imagination.  So what do they do that other survey and photographic equipment does not do.  Let’s look at what they do very well.  They collect very precise points in space and a very high rate of speed and the photography gives the laser  the ability to color these points.  This seems like a simple thing and one could wonder why it is such a big break through.  Because these points are precise one is able to go scan and object and then reproduce that same object in a computer.  Not only reproduce the dots but reproduce almost every feature that comprises that object.

3DLaser Scanner being mounted on a 15’ tripod

3DLaser Scanner being mounted on a 15’ tripod

In 2005 the movie “Troy” was being produced and the need for a very good replica of the Parthenon needed to be built on set in Hollywood California.  You could imagine the amount of work it would have taken to get hundreds of people with measuring devices to go and measure the real Parthenon and then draw up the plans.  This was a perfect job to do with the new 3D Laser Scanning technology.  The movie company hired a scanning company to go over to Italy and make a very thorough series of scans.  From these scans which were accurate with in a ¼ of an inch detailed plans were drawn up and the replica with constructed from the plans produced by the scanner.  The point here is that this is the perfect instrument to completely and thoroughly map existing conditions.  That is one of the strongest features this computer/machine produces.  The first scanners came from LIDAR technology.

LIDAR (Light Detection And Ranging) is an optical remote sensing technology that measures properties of scattered light to find range and/or other information of a distant target. The prevalent method to determine distance to an object or surface is to use laser pulses. Like the similar radar   technology, which uses radio waves, the range to an object is determined by measuring the time delay between transmission of a pulse and detection of the reflected signal. (source wikipedia).

The first uses of this technology were in aircraft mapping the earth surface.  The rapid fire laser technology would send out a light beam at a high speed using a very powerful laser and it would hit the earth and create a point.  With millions and millions of these points  created from the laser pulses a very accurate map of the earth surfaced was generated.  A gentleman named Ben Kacyra understood the technology and with the help of his partners and funding invented the first terrestrial 3D Laser scanner.  His reasoning was that he worked in the piping industry and he was looking for a better way to map complex piping runs in refineries and heavy industrial complexes.  The technology worked well and from there on was expanded in to the more sophisticated scanners we have today.

So the best feature of the scanner is that it can precisely map existing conditions and this ability has been translated into many fields.  A whole new field of 3D engineering has evolved around this technology.  Our first use of the technology was in existing road surveys for the Department of Transportation. LandAir Surveying has a long history of working with the Georgia department of Transportation.  We were surveying a very long bridge over Atlanta’s biggest river and we were having a very difficult time capturing all the existing bridge structure using single point total station survey technology and meeting the specifications.  As an experiment we tried the same work with a 3d Laser Scanner and we captured all the information we needed with little difficulty.  That was our first project and since 2005 we now have completed hundreds of projects.

 

Color scale show change in elevations’ in this 100 year old farm house. In a 3D Laser scan

Some of our more memorable projects included:

Providing our client with a floor as built of a building that was approximately 500,000 square feet.  The client was a contractor and they needed it for their client to determine that the floor met the specification for being level.  In two days we scanned and captured about 10,000,000 points.  Then we presented the data to the client firms in colored contours that we 1/8th inch contours and every time it changed by another 1/8 inch the color also changed.  Ultimately we provided them a 10 foot grid and the floor did meet the specification.

We have surveyed structural walls that were either settling  or sinking and we survey the amount of settlement over a period of time and showed graphically and with excel spread sheet how much movement we detected.

We have surveyed mines both above ground and below and underground and were able to give the client a map of the existing conditions.  In doing this we also were able to keep our crews safer and they did not have to go into the working faces of the mines which can be very dangerous.  Because of the range the laser collects data we were not with in what the miners call the “working face” area which is much more susceptible to falling rock and surrounded by large heavy moving equipment.

As we go forward in this publication we will talk more and more about the different types of projects we have worked on and how the scanner was used to collect information that otherwise could not be collected.

3D Laser Scanning revolutionizing data collection

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3D Laser Scanning technology is currently revolutionizing data collection in every phase of engineering architecture planning manufacturing and design and fabrication.

“…3D Laser Scanning will have an impact on the design and engineering world equal to the digital calculator or GPS technology…”      H Tate Jones 2005

That statement is truer now than it was then.  The technology is not only affecting the design and engineering world it is starting to be used in ways to span the imagination.  There are multiple types of scanners and they range from scanners that literally map the globe on a regular basis, mounted to the space shuttle, to scanners that map your brain and are used by surgeons.  Believe it or not the data format is basically the same from all these different types of scanners.

What is the technology?

Z&F Phased based 3D Laser Scanner

Z&F Phased based 3D Laser Scanner

3D laser scanning is a process involving the use of high speed lasers that fire at incredibly high rates of speed.  There are two different types of scanners that are commonly used in 3D laser scanning in the context that I am writing about.  Phase Based and Time of Flight. Phased base means that a constant beam of laser energy is emitted from the scanner and the change of phase of the laser light is measure to allow the scanner to calculate a distance.  The advantage of this is higher point capture.  Currently up to 2,000,000 points per second.  The down side of this is much shorter range, currently about 30 meters.

Leica ScanStation II Time of Flight 3D Laser Scanner

Leica ScanStation II Time of Flight 3D Laser Scanner

In a time of flight scanner a pulse of light is emitted from the scanner. The time it takes for the pulse to travel from the scanner to the object and back is measured allowing the scanner to calculate the distance. The key benefit to this type of scanner is longer range scanning. The down side of this type is that they do not collect as many points.  Currently they collect about up to 50,000 points per second.  For the reasons above the phase based technology is used inside more often and the time of flight is use outside more often. However best practice is that you used both inside and outside as necessary to get a very precise and accurate scan.

Both of these methods produce millions and sometimes billions of individual points.  The points are located in space geometrically and have a very precise relationship to each other.  As you can imagine this creates a very dense point group.  These millions of points create a geometric hologram currently called a “Point Cloud”.  The point cloud is a very exact replication of the 3D environment in the effective area around the scanner.  So if the scanner is placed inside a building the interior is of that building is shown in great detail.  So detailed that precise measurements can be made of the physical geometry of the surroundings.  This points can be used to capture such irregular surfaces as the interior of an automotive plant with all the cables wires beams and moving parts that are contained in that environment.  These point clouds can measure the buildup of snow on the side of a mountain.  They can measure and represents roads, bridges, historic architecture, streets, towers, trees and millions of more examples. They can also measure very small microscopic items like the inside of a watch or very fine machined parts.

In order to be clear of the terms that are used in this field, below are some common terms that are used in the 3D Laser Scanning field:

Common Laser Scanning Terms:

Point Cloud Millions of points geometrically connected in space which are measurable.

Mesh Small triangles used to make a surface that can be read by a computer.

Modelling Building Cad models inside computer programs that represent building parts and   can be measured and manufactured and tested.

Change Detection Making repeated measurements of the same surface at different times that can detect movement on a surface in the surface.

Clash Detection Comparing design models to other design models or point clouds.

Spherical Photography Photography that can be view in 360 degrees.

Noise Points around a scan that are not the surface of the object but are reflected off the  object.  These can be cleaned and removed from the scan data if necessary.

Traversing Moving a scanner from one point to another and keeping up with the geometry   between points to establish the exact position of the 3D Scanner in space.

Laser Refraction This is caused by the laser passing through a window or opaque surface.  Can also be caused by water. This must always be considered.

3D Scanners in an efficient data collection process

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Understanding How to use 3D Scanners in an efficient data collection process.

There are a few legends and myths about Laser scanners that should be cleared up at the beginning of this article.  First; Laser scanners do not penetrate anything.

Example: of foliage that would prevent a scanner from touching the ground.

Example: of foliage that would prevent a scanner from touching the ground.

You will hear very often that a scanner can go down through deep grass and or thick foliage and always finds the ground.  This is simply not true.  The laser beam will find the lowest point of return before the light no longer returns to the scanner.  Sometimes you will hear or read dialogue talking about first return and last return.  A good example of this is a tree.  The laser beam can hit the ground the bushes then a tree trunk then the bushes then the ground. It cannot really differentiate between the low part of the tree it hit and the ground.  All it detects is that it collected a point.  There is some very interesting technology call Full Wave-Form Technology that can measure the strongest point of the return and increases the chances of finding the lowest point or the hardest point but that is a discussion for another article.  Much research is being done in this area.  The short version is this if you use a Laser scanner to measure ground beneath foliage you are not going to get survey quality results.  I attended a presentation of what at first appeared to be a very good project example of a dyke survey in New Orleans after Katrina.  The problem that was not overcome was that the grass was about 18” high all over the dyke.  The presenter suggested and showed a method of cutting cross sections to pick and find the lowest point or the “ground shots”.  The results were very inconsistent.  The surface that was generated was sometimes the ground and sometimes the top grass and sometimes somewhere in between.

So what is the typical scanning method and best practice?

While all jobs are different they all have certain processes in common.  For this example let’s say that we are going to scan a small campus with several buildings and roads. ( See example below) The job is to create a DTM (digital terrain model) surface and building footprint and elevation views.

Example of Campus Scan mention above

Example of Campus Scan mention above

The first step is to bring in some type of survey control.  Normally two or three GPS survey grade control points.  This will tie the area down on a known coordinate system and allow the users to find it on known data bases like Goggle Earth  or local or state GIS database information.  To start the scan we typically  place two or three targets on the control points to tie down the coordinate system.  Using this example we would scan the road in front of the campus and then the fronts of the buildings.  However notice that there is a hedge between the road and the buildings this will cause several extra set ups to get between the hedge and the road.  Then we would scan through the parking lots and the fronts and backs of all the buildings.  Again we have to take into account the close foliage adjacent to the building but in this case it will have minimal effect on the number of scans.  To scan the roads in front of the campus would likely take 3 to 5 scans.  To scan the front of the buildings you would set up your scanner on the front right side of the top left building so you are getting the side and the front, then again in front of the building again at a point in front of the gap between the buildings continuing on down the line of buildings so that you whenever you can you are scanning the front and sides of the buildings.  When you scan behind the buildings you will also scan at points in front of the buildings and between the gaps.  The point is two always scan as many surfaces as you can from one set up.  Note that when you are scanning the back of the front buildings because of the range of the scanner you are also scanning the front of the buildings in the next row.  At the same time we shoot a series of pictures at each scan points that allows us to produce 360 degree photographs at each set up.  I will go into the photography in more detail in a later article at this is one of the most powerful tools in Laser Scanning.

3D Scanning Process from Start to Finish

3D Scanning Process from Start to Finish

Using this process you could scan the above campus in about 12 to 16 hours depending on the type of scanner you used.  Because there are not really long site lines the preference would be to use a high speed phase based scanner on most of it and perhaps a long range scanner in front on the campus along the road.

When the scanning is completed and the data is processed and registered you can export the information into cad software and then produce the final products of elevation views and a DTM surface model. AutoCAD and Micro Station are still the most common software’s used for this. In the example to the right you see a photograph of a building then the, the scan data that is untouched.  Then you see the scan data after we have colored the points with the photography and then calculated the elevation views of one side of the building.  Just by looking at this example you can see how much more data you get compared to the normal survey using a total station and drawing it in cad.  An interesting note in looking at and viewing scans is that there is always more space between the points than the points take up so you always are looking at opaque views that look more like water colours than photographs.  Because of this when you are using software you can see through signs so when you look at a STOP sign from the other side is appears as POTS with the letters reversed.