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AUCILLA RESEARCH INSTITUTE
ARTIFACT SCANNING LAB
Laser scanning has created an exciting opportunity for the sharing of information on archeological artifacts. Using technology borrowed from land surveying, laboratory scanners measure distances and directions to a dense grid of points on the surface of a scanned object, establishing precise 3-D coordinates for each such point. This results in a three-dimensional high-resolution digital model. The resulting point cloud may be viewed in three dimensions, much as the physical object itself may be viewed. The model may be viewed from any perspective, and precise measurements made of the object. Further, that model can be shared, via the internet, to allow other researchers anywhere in the world to examine and study the artifact, much as can be done with the physical item itself. As a result, leading museums, such as the Smithsonian Institute, are making high-resolution scans of their entire collections, creating virtual museums, open to the world.
To allow the Aucilla Research Institute (ARI) to take advantage of this technology for the advancement of science, the Louise H. and David S. Ingalls Foundation provided a grant for the purchase of equipment and setting up of a scanning lab. The lab is set up in a two-room suite in the Gerry Building in Monticello, Florida. The lab currently is equipped with a high-resolution laser scanner along with an advanced computer system and associated software (Figure 1).
ARI Scanning Lab Equipment
The heart of the scanning lab is a Next Engine scanner. That device “paints” the object being scanned with four bands of an infrared laser (Figure 2) to measure distances and angles and create an amazingly dense image of 67,000 points per square inch. The associated Scan Studio software controls the scanning as well as the alignment and editing of the images. The software operates on a high-level Dell computer complete with dual monitors.
Laser Scanning Process
Items being scanned by the system are placed on a turntable which automatically rotates. This allows the subject to be scanned from several perspectives, creating a three-dimension point cloud from each perspective. A digital photograph is also taken from each perspective to provide color for each scanned point. After scanning, point clouds from each perspective must then be aligned to create a coherent digital model of the subject. A custom artifact holder is used that not only supports the object while it is being scanned, but also provides several miniature surveying targets that can facilitate the alignment process.
There is a considerable art to the entire scanning process. In addition to the painstaking alignment process, scans must be fused into a consolidated model and then carefully edited to remove images of the supporting structure or background noise. While a typical eight-position scan takes about an hour, the alignment and editing process takes considerable more time.
The completed scans are typically downloaded to an OBJ file which may be viewed and
analyzed using various observing software (Figure 3). A typical digital model of a small object is about 100 megabytes in size. Therefore, a key component of the system is high-capacity offline storage for the models.
Typical Model being viewed in Cloud Compare Software
The scanning lab will allow the ARI to provide scanning services for archeological researcher from various universities working in the Florida area. That resource will be an attractive featurefor such researchers, allowing them to immediately document their findings and share them withcolleagues anywhere in the world. It can also be used for scanning items other than archeological artifacts. Potential applications are almost unlimited.
In addition, the ARI has begun to create digital models of significant archeological artifacts from several large collections which have been donated to the Institute, thus creating a virtual museum of the collections. As each item is scanned, entries will be made in an index (Figure 4) which will be posted on the ARI internet site (www.aucillaresearchinstitue.org).
Format for Index of Scans on Internet
Viewers will be able to sort the index using one or more of the data fields in the index. Once item numbers are known for any scans of interest, users may download those models. Once downloaded, scans may be viewed using any of various viewing programs (such as Geomagic Verify Viewer, Cloud Compare or Sketch Fab) which are available for free download. With such viewers, scans may be examined and studied from various perspectives and measurements made on the image. Viewers may even use the downloaded models to create reproductions of the artifacts with 3-D printers which are available at many public libraries, universities and private entities.
An important advantage of the scanning lab is that it will facilitate education in the use of this technology. Plans are being developed to offer training and hands-on experience in this technology to interested college students, possibly through fellowships or directed individual studies.
Based on the above, it may be seen that the scanning lab allows the Institute to provide a valuable support service to scientists studying the archeological resources of the Florida area; it will allow the development of an on-line museum of artifacts from that area; and it will provide for education in a new technology. Thus, it is a valuable resource for the community and represents an important contribution to science.
More information on the ARI scanning lab may be obtained from the following:
George M. Cole, PhD, PE, PLS
USE OF AIRBORNE BATHYMETRIC LiDAR FOR HIGH-RESOLUTION MAPPING OF NEAR-SHORE COASTAL WATERS
George M. Cole, PE, PLS, PhD
TRADITIONAL HYDROGRAPHIC MAPPING PROCESSES
The traditional hydrographic surveying process used for hydrographic mapping during the last few centuries involves taking depth measurements from the surface of the water. Originally, such hydrographic surveys used water depth measurements made with a lead line. That device consists of a sounding lead attached to a graduated and marked line. The advent of echo sounders (fathometers) in the mid-1900s completely revolutionized hydrographic surveying and made surveying in deeper water practical. Echo sounders are devices that measure the time required for a sound wave to travel from its point of origin at the surface to the bottom and return, and then convert the measured time to depth based on the speed of sound in water. Since depths are measured from a transducer, typically mounted on the bottom of the vessel’s hull, a draft correction has to be applied to the soundings for correction to the actual depth of water. In addition, since the water level in most waterbodies changes constantly with time due to tides and/or meteorological conditions, the soundings also must be corrected to a common datum as opposed to the level of the water at the time of the measurement. Such corrections often add uncertainty to the measurements. Recent innovations have resulted in multi-beam fathometers, that measure an array of points simultaneously as well as processes for the use of GPS for vertical control to reduce errors due to uncertain draft and datum corrections. Nevertheless, even with such advances in sounding technology, most hydrographic charts today are based on widely-spaced sounding lines. This is especially true in the near-shore areas since the relatively shallow depths restrict the use of multi-beam fathometers. Therefore, such charts generally do not purport to provide a high-resolution coverage of the submerged lands. Further, the coverage of existing hydrographic charts usually do not include many non-commercially navigable coastal areas or smaller streams and rivers. Yet, due to large-scale rises in sea level since the last glacial maximum, those very areas often contain much evidence of early animal and plant life as well as of past civilizations. Good examples may be seen with two drowned river channels (Aucilla and Econfina Rivers) now located in the shallow margins of the Big Bend area of the Gulf of Mexico. Although not depicted in detail on published charts, those underwater channels contain numerous sinkholes, freshwater springs, and other small features. Further, these areas are rich in archeological resources dating from the very early Paleoindian tradition to the early part of the Middle Archaic when water levels were much lower. At that time, the karst channels and sinkholes were the primary source for water for early humans as well as for other forms of animal life. In addition, this offshore area was extensively quarried by early Native American populations for its Coastal Plain chert resources. Thus, higherresolution mapping of near-shore areas is needed. Such mapping is critical for learning more about the nature of sea level change itself, as well as the effect of sea-level change on the geology and hydrogeology of the earth, and on the adaptation of animal life (including humans) and vegetation to such change.
AIRBORNE BATHYMETRIC LiDAR
One promising approach for higher resolution mapping of shallow underwater areas is laser scanning with airborne bathymetric LiDAR (Light Detection And Ranging). With its capability for high-resolution mapping of topography in tree-covered areas, airborne LiDAR is often used for topo mapping. In addition, tripod- mounted laser scanners are in wide used for delineation of upland topography. Yet, the LiDAR systems more commonly used for those applications use lasers with a wave length in the infrared spectrum which reflects off water surfaces. Thus, those systems are not useful for hydrographic measurements. Fortunately, recent developments in the use of green lasers in airborne scanning have allowed the application of this technology for creating precise digital models of underwater features. LiDAR systems designed for bathymetry use two systems, one in the infrared spectrum with a typical wavelength of 1064 nm and another in the green spectrum with a typical wavelength of 532 nm. The infrared wavelength signal is reflected by the water surface and thus may be used to determine the distance to the water surface. The green wavelength continues through the water and is reflected from the submerged land surface. Thus it may be used to determine the distance to the bottom. (Figure 1).
RIEGL BATHYMETRIC LIDAR
One such bathymetric LiDAR system was developed by the Riegl Corporation. That system is advertised as having a penetration capability of about one Secchi depth down to a depth of 10 meters. That system has been used for the mapping of an ancient submerged Roman harbor site in Kolone, Crotia and of another archeological site in Lake Keutschach, Austria (Doneus et al 2014) . In the Croatian study, penetration depth of up to 11 meters was reported while penetration in Lake Keutschach, which had more turbid waters, was only 1.6 meters. The Riegl system was recently tested by the Suwannee River Water Management District in the Manatee Springs area near Chiefland, Florida (Cole 2014). The coverage of the test included the spring basin itself, the spring run leading from the basin to the Suwannee River, and the river for about 1000 feet above and below the confluence. The area was chosen to provide a wide range of depths and with turbidity conditions ranging from the clear spring water at the spring head to the more turbid Suwannee River as well as representing an area with adverse tree cover conditions. The LiDAR data acquisition was flown at an altitude of 550 meters above ground level. For evaluation of the results, turbidity sampling was performed in the Suwannee River portion of the test area. In the river, turbidity measurements with a Secchi disk in the river resulted in visibility ranging from 12.8 to 14.9 feet. Water clarity was considerably better in the spring basin and run, although, due to restricted access because of the concentration of manatees in the springs during the flight, turbidity readings in the springs were not taken. The LiDAR data produced a high-resolution model of the basin and run for Manatee Springs itself with depths down to about 30 feet (Figure 2). Interestingly, even the manatees present in the springs at the time of the flight were “mapped”. A preliminary analysis of the accuracy of the bathymetric elevations obtained by this technology was performed by comparing the LiDAR measurements with depth soundings at 31 locations in the spring basin and run. That analysis indicated a mean error of 0.10 feet and an error range of -0.63 to 0.35 feet (Karlin 2014). Unfortunately, this was not the case in the Suwannee River itself with its higher turbidity. The bottom trace projected only a limited distance in the Suwannee River (Figure 3). As may be seen, in areas with depths greater than about eight feet there was no bottom reflection even though the Secchi depths in the river ranged from 12.8 to 14.9 feet at the time of mapping. Riegl personnel have suggested that a possible reason for the lack of deeper penetration is the black mud bottom surface in this area which possibly absorbed the laser signal, rather than reflecting it.
Cross Section of Manatee Springs Run and the Suwannee River Note that bottom trace was lost in river for depths greater than 8 feet.
(Courtesy of Suwannee River Water Management District)
TELEDYNE OPTECH BATHYMETRIC LIDAR
Another bathymetric LiDAR that has recently become commercially available is the CZMIL system developed by Teledyne Optech. That system has a claimed penetration of 2.5 Secchi depths down to 80 meters, which is considerable more than the Riegl system which has a claimed penetration capability of one Secchi depth down to about 10 meters. This system has reportedly been used on coastal projects along both the East, West and Gulf Coast of the United States as well as in numerous other coastal projects worldwide. That system is advertised as being ideal for turbid waters and muddy, less reflective seafloors (such as was the case in the Suwannee River at the Manatee Springs project) due to the processing program. Figures 4 and 5 illustrate products of that system at depths as great as 34 meters in an area offshore of Ft. Lauderdale, Florida.
As may be seen from the illustrations presented, airborne bathymetric LiDAR appears to offer an ideal solution for high resolution mapping of underwater features in near-shore waters where conditions allow its use. Further, it allows coverage of areas in shorter amounts if time, allows coverage of areas inaccessible by boat due to shoals and reefs or shallow water, and provides a full 3-D model from the land to the maximum water depth. Therefore, it has great promise for environmental and archeological research. A consortium of federal agencies called JALBTCX is in the process of mapping some of the coastal areas of the United States using bathymetric LiDAR. Yet, such mapping will undoubtedly be concentrated in areas of importance to navigation. As previously mentioned, many of the near shore shallow reaches of the areas such as the Northern Gulf of Mexico contain a treasure of information for hydrological, biological, geological and archeological studies, and research is limited by lack of high resolution bathymetric surveys. Therefore, additional mapping projects using this technology in those areas is encouraged and grant applications for such mapping are pending.
Cole, George M. “Airborne LiDAR Hydrography for Managing Florida’s Water”, Hydrography – More than Nautical Charting, www.nauticalcharts.NOAA.gov. 2014.
Doneus, M, I. Miholjek, G. Mandlburger, N. Doneus, G. Verhoeven, Ch. Briese, M. Pregesbauer. “Airborne Laser Bathymetry for Documentation of Submerged Archaeological Sites in Shallow Water”, The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol. XL-5/W5, 2014.
Karlin, Alvin, personal communication. South West Florida Water Management District, 2014
George M. Cole is a professional engineer, surveyor and geographer and a member of the Board of Directors of Aucilla Research Institute. Cole holds a bachelor of science degree in mathematics from Tulane University as well as master of science and doctor of philosophy degrees in geography from Florida State University. His background includes several years of service (final rank: Lt. Commander) with the U.S. Coast & Geodetic Survey (now part of NOAA); as the State Cadastral Surveyor for Florida; as President of an engineering and surveying firm with projects including LiDAR surveys in Central America; and as a Professor at the University of Puerto Rico. Cole currently serves as a private consultant and continues to serve as an Adjunct Professor at both the Florida State University and at the University of Puerto Rico. Cole has served as technical advisor to several states on boundary issues; and has provided expert testimony to a number of local, state and federal courts. He also has made significant contributions to professional literature and is the author of several surveying textbooks (with notable examples being Water Boundaries, John Wiley & Sons, 1997, Surveyor Reference Manual, Professional Publications, 2009, and Land Tenure, Boundary Surveying and Cadastral Systems, Taylor & Francis, 2016.
IMPLICATIONS FOR FUTURE RESEARCH ON
SEA LEVEL CHANGE ALONG FLORIDA’S BIG BEND COASTLINE
George M. Cole, PE, PLS, PhD
HISTORIC SEA LEVEL CHANGE
Sea level has been in a state of flux throughout the history of the world. A glimpse into that change may be obtained by examining the geologic history of a land mass such as the Florida Peninsula. From about 200 million years ago at the time of the origin of that peninsula until about 23 million years ago, much of Florida was submerged under a shallow ocean accumulating a limestone base layer. In North Florida, the prominent Cody Scarp is a reminder of where the coastline was located during that period. After that time, the sea level began to drop until the time of the last glacial maximum when Florida reportedly had about three times its present land mass. At that time the ice began melting and sea level began rising. The scale of the most recent sea level rise since the last glacial maximum, has been quantified by a report published by the Florida Geological Survey (Balsillie and Donaghue 2004). That report provides an analysis of 341 separate radiocarbon dated sea level indicator points based on 23 independent field studies in the northern Gulf of Mexico. For that report, the authors used a seven-point averaging process after converting the elevations for each point to absolute years from radiocarbon years, considering 1950 as zero or present sea level. When the results from that report are plotted, they provide a good overview of the trend of sea level in the northern Gulf of Mexico over the last 22,000 years (Figures 1 and 2). As may be seen from those figures, a least squares regression through those points suggests an average rise of 6.0 mm/year over the last 22,000 years, and 2.3 mm/year over the last 10,000 years. Those changes are considered to be associated with melting of grounded ice, thermal expansion, and redistribution of water mass, all associated with the long-term climate change that has taken place during the last 20,000 years or so.
Estimated Sea Level Change over Previous 22,000 Years
Based on data from Basillie and Donaghue 2004
Average rate of rise over depicted period: 6.0 mm/yr
Over 1st 10,000 yrs: 10.4 mm/yr, Over last 10,000 yrs: 2.3 mm/yr
The above trends reflect averages over many thousands of years. Within those periods, there were numerous short term trends with periods of a few hundred years or so, with sea level trends considerably different from the average over the entire period (Figure 3). As examples, from about 150 to about 950AD, a period of about 800 years, the data suggest a falling sea level trend of -3.0 mm/yr. At the beginning of that period the data indicate that sea level was more than a meter above current levels. That downward trending period was followed by about 1000 years (from 950AD to present) with a rising slope of about 1.5 mm/yr. Within that 1000-year period, there was a sub-period of rapid rise (950 – 1250) during the so-called “medieval warm period”; and another of rapid decline during the “little ice age” (1300AD and 1850AD) when much of the world was subjected to cooler winters than in subsequent centuries.
RECENT SEA LEVEL CHANGE
In more recent history, records from sea level gauges are available that allow direct observation of the rate of sea level changes (Cole 1997), as opposed to reliance on the dating of sea-level indicators. The longest operating of such stations worldwide is in Historic Sea Level (m) Relative to 1950 Level -2 -1.5 -1 -0.5 0 0.5 1 1.5 0 500 1000 1500 2000 Year (AD) 4 Brest, France which has been recording sea levels since 1807. The station with the longest records in the United States is San Francisco, established in 1855, which indicates an average rise of 1.89 mm/year (Figure 5). As may be seen, the data for that station records reflect a relatively constant slope over the century and a half period. For the same period, the Brest, France station has a rate of 1.30 mm/year. Those rates also reflect global averages per the following statement of the Intergovernmental Panel on Climate Change (IPCC 2001):
“Based on tide gauge data, the rate of global MSL rise during the twentieth century is in the range of 1.0 to 2.0 mm/year, with a central value (not necessarily the best estimate) of 1.5 mm/year.”
It is noted that these trends are over relatively short periods of observation compared to those based on carbon dating previously presented.
Along the Florida coastline of the northern Gulf of Mexico, the National Oceanic and Atmospheric Administration (NOAA) maintains long-term gauges at Cedar Key, Apalachicola, Panama City and Pensacola. Plots of annual mean sea level for those stations using all available data, along with the average rates of increase, are provided in Figure 5.
Annual Mean Sea Level Based on NOAA Data
Annual Rates of Sea Level Change:
Cedar Key: 1.89 mm/yr, Apalachicola: 1.76 mm/yr
Panama City: 1.60mm/yr, Pensacola: 2.19 mm/yr
By observing gauging data at various locations, it may be readily seen that the apparent rates of sea level rise as measured by gauges appear to vary somewhat with location. This is in large part a result of local land motion rather than actual sea level change. As an example, progressing westerly from along the northern coast of the Gulf of Mexico, there is an increase in the rates of apparent sea level rise as illustrated in the following table (data from tidesandcurrents.noaa.gov):
Station Rise (mm/year)
Panama City, FL 1.73
Pensacola, FL 2.21
Dauphine Is., AL 3.10
Bay Waveland, MS 3.93
Grand Is., LA 9.03
New Canal, LA 4.50
Sabine Pass, TX 5.42
Galvanston, TX 6.34
Rockport, TX 5.27
Corpus Christi, TX 3.50
Port Isabel, TX 3.79
As may be seen, that increase culminates in areas along the Louisiana coast where there is the highest apparent rise in the United States (e.g. 9.03 mm/year at Grand Isle). The differing apparent rises are believed to be related to local land movements. Since sea level changes are measured relative to a fixed bench mark on land, measured sea level changes include both true sea level changes and vertical land movement due to various factors including earthquakes, tectonic motion, consolidation of coastal sediments, consequences of extraction of oil or water, and responses of the earth to the melting of glaciers (Pugh 2004).
The effect of local land movement on apparent sea level is graphically illustrated by comparing data for sea level change at Grand Isle, Louisiana and from Southeast Alaska. There is a decline in apparent mean sea level of 13.2 mm/year at Juneau, believed to be related to glacial rebound. Continuous GPS observations at both Juneau and Grand Island, Louisiana confirm the effect of the suspected local land movement (Figure 6). GPS observations at Juneau indicate a current uplift rate of approximately 13.6 mm/year which implies that actual sea level rise at Juneau would be roughly ( -13.2 –(- 13.6)) or 0.4 mm/year. At Grand Isle where the apparent sea level rise is 9.03 mm/year, GPS observations indicate a current subsidence rate of approximately 8.1 mm/year which implies that actual sea level rise at Grand Isle would be roughly (9.03 – 8.1) or about 0.9 mm/yr. Therefore, in some areas, local geological mechanics are a greater factor in apparent sea level rise than actual sea level.
IMPLICATIONS FOR FUTURE RESEARCH
As may be seen from the previous two sections, (and contrary to popular misperception possibly caused by misleading sensational media) sea level rise is not a new phenomenon. Rather, sea level has been in a state of flux throughout the history of the world. Further, contrary to some popular beliefs, the rate of actual sea level rise does not seem to have increased significantly over the last century. Nevertheless, sea level has generally been on a significant upward slope over the last 20,000 years since the last glacial maximum and continues to be so today. Further, that rise has and will continue to have a significant impact on vegetative and animal life, including humans. Moreover, considering the nature of modern civilization today with its more developed coastal infrastructure, changing sea level will probably have far greater impact today than earlier in the history of the earth.
As a result, there is a significant need for research in not only the nature of sea level change itself and its relationship to climate and crustal motion, but also on its effect on the geology and hydrogeology of the earth, on how animal life and vegetation adapt to such change, and the effect of that change on mankind and modern civilization. The Big Bend area of Florida offers an ideal laboratory for such studies. That area was home to one of the earliest human populations in the United States which was obviously affected by sea level change. The area also has seen an amazing variety of other animal and plant life over the history of the North American continent which has been affected by sea level change. In addition, the area offers spring-fed rivers, a unique karst geology, and an important aquifer immediately adjacent to and under the coast that are all strongly affected by sea level change.
Specifically, the following research is needed in this region:
- Considering the rise in sea level over the last 20,000 years, much of the evidence needed for the suggested research into the nature and impact of sea level change lies beneath the near-shore waters, an important step towards such research is the development of high resolution maps of those waters. Almost all existing hydrographic charts are based on widely-spaced sounding lines. Although helpful for navigation, they do not provide a high-resolution coverage of the submerged lands. Further, the coverage of existing hydrographic charts often does not include many non-commercially navigable coastal areas or any significant areas up streams and rivers. Therefore, a data base of high-resolution maps createdwith a technology such as bathymetric LiDAR (see Cole 2014) is essential for future research.
- Possibly the most important ingredient for research on sea level change is a dense network of continuously operating water level gauges. NOAA has been diligently working towards that goal. Yet, the Gulf Coast between Cedar Key and Apalachicola is one of the longest stretches of shoreline in the U.S. where there is no real-time automated monitoring of sea level. Such a gauge together with frequent ties to high stability bench marks for this area is needed.
- Associated with the need for such a gauge is the need for continuous, or frequently scheduled, GPS observations at the gauge to allow separation of true sea level change and land motion.
- NOAA ‘s National Geodetic Survey coordinates a network of GPS stations, some of which are co-located with tide stations. There is a need for a systematic nation-wide analysis of data from those stations to get a truer picture of actual sea level change nation-wide as well as vertical land movement which has the same effect as sea level change.
- There is need for systematic archeological studies of the impact of sea level change on the distribution and adaptation of plant and animal life in the past, including studies of past human settlements in areas now covered by the Gulf , how such settlements were affected, and how they adapted.
- Considering the numerous freshwater springs in areas now under the waters of the Gulf in the Big Bend, there is need for hydrogeological studies to examine the effect of sea level change on these springs and on the water of the Floridan Aquifer feedig those springs.
- In addition, on a closely related topic, there is a need for research into the long-term trends of the level of the Floridan Aquifer considering both the changing level of the aquifer as well as salt water intrusion. Both of are closely related to sea level change and are of significant importance to future land use planning.
Together, such suggested research will help to not only better understand the nature of the continuous sea level change, but should also provide a sound basis for better coastal planning for adaptation in coastal areas.
Balsillie, James H. and Joseph F. Donaghue. “High Resolution Sea-Level History for the Gulf of Mexico since the Last Glacial Maximum”, Florida Geological Survey Report of Investigation No. 103, 2004.
Cole, George M. “Airborne LiDAR Hydrography for Managing Florida’s Water”, Hydrography – More than Nautical Charting, www.nauticalcharts.NOAA.gov. 2014. Cole, George M. Water Boundaries, New York: John Wiley & Sons, 1997.
Intergovernmental Panel on Climate Change (IPCC). Cambridge: Cambridge University Press. 2001.
Pugh, David. Changing Sea Levels, Cambridge: Cambridge University Press. 2004.
George M. Cole is a professional engineer, surveyor and geographer and a member of the Board of Directors of Aucilla Research Institute. Cole holds a bachelor of science degree in mathematics from Tulane University as well as master of science and doctor of philosophy degrees in geography from Florida State University. His background includes several years of service (final rank: Lt. Commander) with the U.S. Coast & Geodetic Survey (now part of NOAA); as the State Cadastral Surveyor for Florida; as President of an engineering and surveying firm with projects including LiDAR surveys in Central America; and as a professor at the University of Puerto Rico. Cole currently serves as a private consultant and continues to serve as an Adjunct Professor at both the Florida State University and at the University of Puerto Rico. Cole has served as technical advisor to several states on boundary issues; and has provided expert testimony to a number of local, state and federal courts. He also has made significant contributions to professional literature and is the author of several surveying textbooks (with notable examples being Water Boundaries, John Wiley & Sons, 1997, Surveyor Reference Manual, Professional Publications, 2009, and Land Tenure, Boundary Surveying and Cadastral Systems, Taylor & Francis, 2016.