Utilizing LiDar on Dos Hombres to Gran Cacao Transect
Utilizing LiDAR on the Dos Hombres to Gran Cacao TransectAmber V. WadlingtonAnthropology 350 Method and Theory in ArchaeologyProfessor Marisol Cortes-RinconDecember 7, 2012
Wadlington 2LiDAR or Light Detection And Ranging is a modern tool that can generate highlyaccurate terrain models that are used in Geographical Information Systems (GIS). LiDAR dataand acquisition are the future of aerial survey and have been used with great success at manyarchaeological sites around the world.Recently at the Mesoamerican archaeological sites ofCaracol, Cayo, Belize and Angamuco, Mexico, great success has been achieved using thisgeospatial innovation. Dr. Diane and Arlen Chase, archaeologists at the University of CentralFlorida in Orlando utilized LiDAR in their research at their sites in Belize and Mexico.Theyclaimed that,“LiDAR-derived data act as a permanent horizontaland vertical document ofeverything on the landscape including archaeological remains, vegetation, topography at the timethe data are collected, thus also recording the status of site preservation and looting,deforestation, and modern construction at a single point in time”(Arlen F. Chase et al. 2011).Using LiDAR systems to map a 12.4 km transect at the Dos Hombres to Gran CacaoArchaeology Projectwill provide extremely useful terrain models and GIS data and it will alsoprovide students and faculty training with hardware function, software function and datamanipulation. By providing students and faculty a chance to utilize LiDAR we will be taking astep into the future of survey technology.This project will provide highly accurate detailed dataofthe site andit will do so in an extremely efficient manner.The Dos Hombres to Gran Cacao Archaeology Project is headed by archaeologist Dr.Marisol Cortes-Rincon of Humboldt State University. It is located in the Northwest region ofBelize in the Orange Walk District see figure 1. The Dos Hombres to Gran Cacao ArchaeologyProject is under the Programme for Belize Archaeology Project (PfBAP) in the Programme forBelize Conservation and Management Area.Dos Hombres to Gran Cacao Archaeological Site iscurrently working to add to the comprehension of how ancient polities were organized in the
Wadlington 3central Maya lowlands of Belize.The study focuses on the investigation of economic andpolitical organization between the Mayan sitesDos Hombres and Gran Cacao. Settlementmapping and analysis of the area between these two sites is integral to this investigation. GranCacao is located 12 km northeast from Dos Hombres. There are future plans for investigation ofan eight mile transect between Great Savannah and Dos Hombres.As well as a four km transectbetween Great Savannah and Gran Cacao. The site is densely forested and as such survey is avery slow process. Arial and Satellite imaging of the surface of this transect is almost completelyuseless because the surface of the ground is all but visible. There is however one very usefulexception and that is LiDAR(Dos Hombres to Gran Cacao Archaeology Project2011 InterimField Report 2011).Figure 1 Dos Hombres to Gran Cacao transectArchaeologists have hailed LiDAR as a catalyst for change in the way we conductArchaeology. The resolution of surface features that can be detected is unparalleled.Advancedpost processing of the data has the ability to break through canopy cover and reveal previouslyhidden archaeological features(Devereux, Amable, P. Crow, et al. 2005). The technology thatLiDAR uses is very complex however the way that it functions is a fairly simple concept.The
Wadlington 4LiDAR hardware is mounted to an airplane or helicopter.It includes a powerful laser that hasboth a transceiver and a receiver(Parcak 2009). Thousands of small bursts of laser energy areaimed at the ground and are emitted from the transceiver on an airplane or a helicopter(Young2011). Each laser point of energy is then reflected back and absorbed by the receiver(Young2011).The laser sensors pulse laser beams that penetrate tree canopies and otherobstructions(Fernandez Diaz 2011).Each pulse of laser spreads out in a cone shape as it reachesfurther from its source; when it reaches the ground it creates a circular area on the ground(Hesse2009). The circular area is called the “footprint” and is anywhere from 10 to 15 meters indiameter(Hesse 2009). If the “footprint” reaches a flat area all the light is reflected back all at thesame time, however if it hits a laser permeable facade such as a forest canopy some of the lighttravels further down and is reflected at a later moment(Devereux, Amable, P. Crow, et al. 2005).A powerful laser pulse and a canopy with gaps in it will produce the highest amount of datapoints that reach the ground(Fernandez Diaz 2011). The first part of the distribution whichcomes from the top of the tree canopy is called the “first pulse” and when it reaches the ground itis called the “last pulse” See figure 3. Swath’s that overlap increase the amount of lasers thatreach the ground(Devereux, Amable, P. Crow, et al. 2005).They are then recorded by a laserscanner. The time is recorded between when the laser was emitted and received, that number isbroken in half and multiplied by the speed of light(Crutchley and S. Crow 2010).The inertialmeasurement unite or IMU measures the altitude of the sensor on its platform it is called the roll,pitch, and heading of the platform(Crutchley and S. Crow 2010).The mounted GPS reports thelocation of the platform of the sensor, or where the aircraft is carryinga LiDAR system(Hesse2009). The points that are recorded by the system relate the data to actual points on the ground inconjunction with a GNSS base unit positioned on your project site(Young 2011). Relevant
Wadlington 5longitude, latitude, and elevation (x,y,z) position for every data point are collected andtransmitted to the base unitand are recorded(Young 2011).Measurements can be as precise as3cm to the actual height(Crutchley and S. Crow 2010). The GPS data points or “point cloud” isthen used to create a computerized 2D or 3D Digital Elevation Model (DEM) of theground(Young 2011). Even before the survey is complete, the data collected can be uploaded tocomputers where digital elevation models, can be accessed to start the analysis process of thesurvey(Aerial Surveying INC. 2012).Software can then convert the data into a variety of formatsincluding LAS, ASCII, ESRI and CAD(Aerial Surveying INC. 2012). The most common use ofthe data is with 3D CAD(Young 2011).The best way to understand how LiDAR will work is toinvestigate its use on archaeological sites in Cayo and Carcol in Belize andAngumunco, Mexico.Figure 2 How LiDAR works
Wadlington 6Figure 3 How LiDAR penetrates the canopyDr. Arlen and Diane Chase Maya archaeologists at the University of Central Florida havebeen conducting archaeological research and survey in Belize for the last 25 years. In specificthey have been conducting survey at Caracol for the last 25 years(Arlen F. Chase et al. 2012).Caracol is described as the largest site in the Southern Mayan lowlands and the site isapproximately 200 see figure 3(Arlen F. Chase et al. 2011). The Chases attained a grantfrom NASA in 2009 in order to conduct a LiDAR survey that would reveal the surface of their200 site below the dense rainforest canopy(Arlen F. Chase et al. 2011). This covered nearlythe entire Vaca Plateau. The National Center for Airborne LiDAR mapping a part of the NationalScience Foundation employed graduate students and professors from the University of Houstonand the University of Berkley (Fernandez Diaz 2011).The survey successfully displayedpreviously mapped and unmapped features of the entire 200 area it included undiscoveredstructural groups, agricultural groups and causeways(Arlen F. Chase et al. 2011). Because of thisthey were able to identify the entire Vacaplateau as single city(Arlen F. Chase et al. 2012). The
Wadlington 7LiDAR survey was done with an OPTEC Airborne Laser Terrain Mapper(Arlen F. Chase et al.2011). The survey was done May 26ththru the 30th, because the end of the dry season in Belizeprovides the maximum amount of “leaf off” conditions which provides the most groundvisibility(Arlen F. Chase et al. 2011). There was 23 hours of flight time with over 9 hours oflaser use(Arlen F. Chase et al. 2011).They flew a dual engine Cessna at an altitude of800meters(Arlen F. Chase et al. 2012). They flew 62 north-south flight lines and 60 west-east flightlines spaced at 260 meters(Arlen F. Chase et al. 2012).They overlapped the coverage by 200%(Arlen F. Chase et al. 2012). The airplane traveled at a ground speed of 80 meters per secondand the pulse rate of the laser was 100 khz. 2.38 billion Lasers were fired which provided 4.28billion measurements and 1.35 laser shots per reached the ground(Arlen F. Chase et al.2011).These features were terraces and as much as 15% more plaza surfaces were revealedthrough LiDAR than through ground survey(Arlen F. Chase et al. 2011). Features that werepreviously missed during ground survey weredue to the growth of the rainforest, LiDAR hassuccessfully broken through these barriers(Arlen F. Chase et al. 2011).Figure 4 Caracol, Belize Site
Wadlington 8I took the time to weight some possible optionson how I was going to conduct a LiDARsurvey of the Dos Hombres to Gran Cacao Archaeology site. Two basic options includepurchasing the LiDAR equipment or planning out a survey of our own and hiring a professionalto conduct the survey that would provide us the option to participate in data collection. Iresearched and attempted to contact many different companies that provided LiDAR services andfound it quite hard to get a hold of anyone. I emailed and called several companies multipletimes and was never able to get a hold of them. This was quite frustrating as I would havepreferred to have a variety of options to choose from. I contacted a few companies that did notwork outside of the USA. I also searched for companies within Belize itself and was unable tofind any at all. I found companies all over the world that used LiDAR; however there are manydifferent uses for LiDAR and it is utilized in a variety of different ways. Finding a company thatconducted airborne LiDAR in Belize was a task however I was successful. I contacted LiDARdealers that sold systems from companies likeLeica, Optech and Riegl(Lemmens 2009). Throughcontact with multiple sales representatives for companies Leica, Optech and Riegl I have foundthat purchasing a quality turnkey airborne LiDAR system ranges on average from 800,000 to 1million dollars see figure 5.They include all hardware necessary to conduct the survey. Theyusually include software for post-processing. However it does not include a computer to run thesoftware or utilize the software. It also does not come with a Survey grade dual-frequency basestation, or equivalent accuracy reference station source or GPS station(Lemmens 2009). In orderto use the equipment it must also be insured for the full cost the initial purchase(LiDAR Services2012). There is an exemption for paying duty on items brought in for scientific research howeverthe sheer value of the merchandise may complicate the situation(Belize 2000). We would need to
Wadlington 9procure a pilot who was skilled in conducting a LiDAR and aircraft to conduct the survey. Theprocess of attempting to plan this venture would be extensive and cost preventative.Figure 5 Turnkey LiDAR EquipmentI found a Company called Aerial Surveying Incorporated that is headed by ThomasPattison. The company is based out of Hawaii. They have done LiDAR work in Belize in thepast. This company provides the hardware, aircraft and software. According to Thomas Pattisonand his web site aerialsurveyinginc.comthey will provide a survey grade dual-frequency basestation, reference station sourceor a GPS station.High grade digital photos will also be provided.Students and faculty will be able to work and observe data collection at the base station andobserve hardware when mounted on the plane. A high end computer must be obtained for postprocessing. Software must also be purchased in order to fully utilize the 3D Digital ElevationModels.Aerial Surveying, Inc. will fly aerial surveying missions anywhere in the World toproduce topographic maps that are construction grade, create 3D Digital Elevation Models, anddo Flood Plane Mapping Analysis. Their “in-house” land surveying department does all of theirground calibration to verify the accuracy of their aerial surveying data. Land surveying serviceson each project include, on the ground survey of dense canopy areas, locating property cornersandconnecting LiDAR data points to those corners. Ground calibrations are done to verify aerial
Wadlington 10LiDAR data and are included. The collected aerial LiDAR data is used to produce 3D DEMs,topographical maps showing land contours, plus information for flood plain analysis and flooddrainage mapping. They use an AutoCAD or a .dxf format which they will upload to their FTPserver that can be accessed easily. An “as-built” survey can be added to your base map. Aerialphotographs are taken during the flight missions for every project and are included at no extracharge.I decided that purchasing LiDAR equipment and planning a survey would be far tooexpensive. I chose to hire professional LiDAR surveyor Thomas Pattison from Aerial SurveyingIncorporated(Aerial Surveying INC. 2012).Planning a survey and creating a budget for a survey requires a great deal of planning. Ihave attempted to make a rough plan and estimate that could be used as an outline for theproject. Two professors and four students will travel to Belize and meet up with his crew in lateMay or early June of 2014. This time is important because it is at the time when the most leaveswill be off the trees providing the greatest ground visibility(Arlen F. Chase et al. 2011).It shouldalso align with the end of the spring term and the beginning of the field school session. Twofaculty members and four students will travel to Belize and meet up with Thomas Pattison andhis crew. This survey should last no more than a week and as little as one day. Thomas Pattisonprovided a rough estimate for conducting this LiDAR project of 38,000 dollars.If the survey atCaracol only took four days to complete our project should last no more than a week but couldtake as little as one day(Arlen F. Chase et al. 2011). I estimated the cost for transportation,lodging, incidental expenses, educational resources, software and a computer at 20,000 dollars.This estimate is very rough and would require more research to come up with a solidbudget.With my rough budget and Thomas Pattisons’ estimate we would need to figure in a 15% cut for
Wadlington 11The Programme for Belize Archaeology and a 22% cut for Humboldt State University we wouldneed a total of 107,000 dollars.As you can see airborne LiDAR will be an efficient effective and transformative way toprovide students and faculty experience with LiDAR and an enormous amount of data for futuresurveying and excavation on the Dos Hombres to Gran Cacao Archaeology Project. This projectwill provide students and faculty a chance to utilize LiDAR and will also provide highly accuratedetailed data of the site.This project aims to give students a chance to be on the cutting edge oftechnology in archaeological mappingLiDAR data and acquisition are the future of aerial surveyand have been used with great success at many archaeological sites around the world. I wouldlike to make the Dos Hombres to Gran CacaoArchaeological project one of those success stories.I explained how LiDAR works, and how it was successfully utilized by other professionalarchaeologists in Belize. I also provided an outline of theplanned LiDAR project and provided arough budget for it.Using LiDAR systems to map a 12.4 km transect at theDos Hombres to GranCacao Archaeology Project will provide extremely useful terrain models and GIS data and itwill also provide students and faculty training with hardware function, software function anddata manipulation. This will help the archaeology project answer questions about how ancientpolities were organized in the central Maya lowlands of Belize. It will also add to theinvestigation of economic and political organization between the Mayan sites Dos Hombres andGran Cacao. It will also provide enhanced settlement mapping and theanalysis of the areabetween these two sites.By providing students and faculty a chance to utilize LiDAR we wouldbe taking a step into the future of survey technology which will not only provide a highlyaccurate detailed data of their site but it will do so in an extremely efficient manner.
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