Since 1987, CRA has routinely incorporated near-surface geophysical techniques in its own cultural resource management projects and has offered these services to clients. CRA owns state-of-the art equipment including duplexed Geoscan FM256 gradiometers; a Geonics, Ltd. EM38 electromagnetic (conductivity) meter; a TR Systems, Ltd. TR/CIA twin-probe resistivity meter; and a Geophysical Survey Systems Incorporated SIR-3000 Ground Penetrating Radar (GPR) equipped with a 400 MHz center frequency antenna and survey cart. Results are processed using a variety of software, importantly Geoplot, RADAN 6, Snuffler, and Surfer, and results are prepared for our clients using Didger, ArcGIS, and AutoCad.
At CRA we stress the use of multiple survey techniques to gain maximum information in a cost efficient manner. Using high speed, high-density data collecting field equipment and up-to-date processing software, we have a continuing commitment to increasing the utility and accuracy of geophysical survey data in both cultural resource management (CRM) projects and non-CRM archaeological research.
Geophysical Survey - Cultural Resource Analysts, Inc. (CRA)
Russ Quick conducting a GPR survey
Russ Quick conducting a GPR survey
Berle Clay conducting a magnetometer survey
Berle Clay conducting a magnetometer survey
Applicability of Geophysical Surveys
The survey techniques used at CRA are applicable to a wide variety of sites and variable site conditions. We are dedicated to providing service to the fast-paced world of CRM. The "ideal" survey site would be a manicured lawn with no ornamental plantings, buildings, or any other above-ground obstructions. We have yet to survey such a site. The techniques we use are applicable to open woodlands, provided there is no undergrowth or the undergrowth can be removed, various types of pastures (mowed and standing), crop stubble, and tilled fields. The rule of thumb is that if the site can be walked at a speed of approximately one meter per second without major obstacles (like downed trees and low hanging tree limbs), it can be surveyed. With proper planning, even sites with obstacles can be surveyed; however, obstacles that impede movement, changing the walking pace, or cause the operator to vary the orientation of the carried instrument can introduce noise into the data and making it difficult to interpret.
Fresh agricultural tilling (plowing and disking) does modify the distribution of resistive, magnetic and conductive constituents in the soil and this disturbance is reflected as cultivation or crop "marks" when such fields are surveyed. These tend to become less prominent over the months as the topsoil "stabilizes and homogenizes" due to weathering. Geophysical survey does tend to record the effects of agriculture long after a field has been fallowed, though. We regard these crop striations not simply as noise, but as an important record of modern impacts to a site. Nevertheless, in designing field strategies that will involve geophysical survey, we recommend that surface scarification (for example to facilitate controlled surface collecting) not be used, at least until the geophysical surveys have been completed. Strip plowing should be avoided.
Speaking from our mid-America experience, geophysical surveys may be conducted at all times of the year. We have encountered most problems with extreme heat, but we use specific techniques to control the effects of heat that can cause sensitive electronic equipment to drift, affecting the quality of the data. For best results, the ground should be dry underfoot so that the operator does not collect mud while walking, which can distort magnetic readings in certain types of soils. Electromagnetic surveys, while they are affected by total soil moisture (importantly, a heavy rain during an EM survey can shift the measurement of earth conductivity significantly), appear to be far less susceptible to total soil moisture than soil resistivity surveys that tend to be unproductive when the soil is either saturated or extremely dry.
The techniques we use that involve magnetics have circumscribed utility in urban contexts with a record of building, demolition, and rebuilding. The problem is metal targets of all sorts. The random metal target produces a major disturbance of the magnetic field surrounding it, at least as it is recorded by a magnetometer or a earth conductivity meter. This obscures the weaker signals that reflect the archaeological targets that we seek (like burned posts, hearths, house floors, etc.). Soil resistivity and GPR can be still be used in these areas.
3D image showing graves that CRA identified with Ground Penetrating Radar (GPR)
3D image showing graves that CRA identified with Ground Penetrating Radar (GPR)
After considerable field experience with the site type, we have concluded that near surface geophysical surveying techniques of all types can be useful for defining historic cemeteries. There are exceptions: pioneer era cemeteries that have become overgrown with trees and children’s burials can be difficult to identify. Most geophysical techniques can define a cemetery’s past, enclosed limits, and this knowledge is important in certain CRM situations. In certain situations, geophysical techniques can provide precise locations for individual graves, but this depends a great deal on the age of the cemetery, the soils, and the “standardness” of the graves. Not every technique works well for delimiting cemeteries. This becomes glaringly apparent when a historic cemetery is excavated as part of its relocation (a practice which we find is becoming increasingly important in CRM archaeology). The reasons for this seem to be that the act of historical burial is a very "brief" geophysical episode and, depending on soil type and grave depth, one that generally causes minimal geophysical modification of the soil or, as in the case of agricultural tillage, modification that is erased with weathering over time. However, the use of multiple, complimentary geophysical techniques (e.g. magnetometry and GPR) often produces a more accurate record of a cemetery than simply probing the soil.
A Note on Research Design
Since they involve intensive ground coverage, the near-surface geophysical survey techniques we use are generally not cost effective in phase I, site discovery surveys. They have an obvious place in phase II, site evaluation. Integrated as the "leading edge" of a phase II evaluation which may involve intensive shovel testing, excavated units, and surface scrapes, they provide a wealth of data that can be used to inform the traditional field techniques which follow in the evaluation. Geophysical surveys never replace conventional data collecting techniques. They can significantly reduce the cost of phase II evaluation by, for example, eliminating area disking and controlled surface collection, which is labor and time intensive and, to the extent that they aid in a better definition of site parameters, lead to both better evaluations of significance and, in the case of a National Register of Historic Places eligible site, cost effective, informed mitigation plans. Often as not, geophysical techniques are used to inform archaeologists where not to dig to achieve the best results during a survey!
Field Protocols (how we collect data)
CRA uses magnetic gradient, electrical resistivity, GPR, and earth conductivity survey techniques that have proven applicability to a wide range of survey conditions and all seasons. Normally, geophysical survey data are collected on CRA projects in 20-m squares and the average survey time for a square is 20–25 minutes. Within a square, readings are taken at measured intervals along transects typically spaced .5–1 meter apart for a total of 1,600–3,200 readings per 20-m square. With both the magnetometers and the earth conductivity meter, readings are routinely taken at 12.5-cm intervals. The GPR routinely takes readings at 2-cm intervals in the horizontal direction with 512–1,024 samples in the vertical direction, vastly increasing the number of readings without appreciably increasing survey time.
Grids are marked with non-magnetic materials, typically plastic pin flags. CRA has found that a major source of "noise" in magnetic and electromagnetic surveys is wire pin flags used by archaeologists in early stages of their field research. We recommend that plastic flags or wooden stakes replace wire pin flags if geophysical survey is contemplated at any future point in the research program at a given site. It is advantageous to remove “field metal” (e.g. horseshoes, bits of farm equipment, etc…) from the site during the field walking stage for the same reasons.
Geophysical Survey of 33Ms591, Meigs County, near Racine, Ohio. Prepared for ODNR, Columbus, Ohio, Project #W09G003, Contract Publication Series 09-XXX.
Ground Penetrating Radar Survey of the Groveport Cemetery, Groveport, Ohio.
Geophysical Survey of Livingston Park Cemetery in the City of Columbus, Franklin County, Ohio. Prepared for EMH&T, Columbus, Ohio, Project #K09E007, Contract Publication Series 09-115.
Geophysical Survey of 15Ms126, Mason County, Kentucky, Near Maysville, Kentucky. Prepared for DEA/KYTC, Frankfort
2008
Geophysical Survey of 33Le673, Lawrence County, Ohio, Near South Point, Ohio. Prepared for PAST, Columus, Ohio, Project #K08p006, Report # 08-100.
GRW Aerial Surveys, Lexington, Kentucky.
2007
Geophysical Survey of 33L3680, Lawrence County, Ohio. Prepared for Weller & Associates, Cultural Resource Analysts, Inc. Contract Publication Series 07-RG1.
Geophysical Survey of 22As32, Ashland County, Ohio, Near Ashland, Ohio. Cultural Resource Analysts, Inc., Contract Publication Series 07-GS3.
Geophysical Survey of an Archaeological Site Near Hebron, Boone County, Kentucky, Prepared for Ryan Weller & Associates, Inc.
Geophysical Survey of Daines Mound 1, Athens, Ohio. Prepared for Evans, Mechwart, Hambleton & Tilton, Inc., Columbus, Ohio.
2006
2006 Geophysical Survey at the Site of Werowocomoco (44GL32), Gloucester County, Virginia. Report Prepared for Department of Anthropology, College of William and Mary.
Geophysical Survey of the Baker's Bluff Site (33Li1094/1096) Licking County, Ohio, FRA/LIC-161/37-23.15/0.00, PID No. 12139, Prepared for Ohio Department of Transportation, Cultural Resource Analysts, Inc. Contract Publication Series.
2005
Geophysical Survey of Various Archaeological Sites in the Avenue of the Saints, Missouri Department of Transportation.
2004
Geophysical Survey of Portions of Sites 78 and 136 in the Ravensford Archaeological District, Cherokee, North Carolina. Prepared for TRC Garrow Associates, Cultural Resource Analysts, Inc., Contract Publication Series 04-067.
Geophysical Survey of 400 Square Meters of the Fort Jefferson Archaeological Site, Ballard County, Kentucky. Prepared for Dr. Kenneth Carstens.
Geophysical Survey of Site 12CL648 for the INAAP Reuse Authority, Jeffersonville, Indiana. Prepared for INAAP Reuse Authority. Cultural Resource Analysts, Inc. Contract Publication Series 03-162.
2002
Geophysical Survey of Certain Areas of the Sewanee University Campus, Sewanee, Tennessee. Prepared for Dr. Major McCollough, Sewanee University, Cultural Resource Analysts, Inc., Contract Publication Series 03-85.
Geophysical Survey at the Harman Blennerhassett Mansion, Blennerhassett Island, West Virginia. Prepared for the Blennerhassett Historical Foundation, Inc., Cultural Resource Analysts, Inc., Contract Publication Series 02-126.
Geophysical Survey at Dunlap's Station near Cincinnati, Hamilton County, Ohio, Prepared for Gray & Pape, Inc., Cincinnati, Ohio.
Geophysical Survey at Three Archaeological Sites in the Natchez Trace Parkway Near Natchez, Mississippi. Prepared for the National Park Service, Southeastern Archaeological Center.
2001
Geophysical Survey of Sites 31SW1 and 31SW2 within the Kituwha Archaeological District, Swain County. North Carolina. Report prepared for the Cultural Resources Department Eastern Band Cherokee Indians, Cultural Resource Analysis Inc. Contract Publication Series 01-71.
Geophysical Survey at the French Dwelling Site, 22AD557, Natchez, Mississippi. Report Prepared for the National Park Service, Southeastern Archaeological Center.
Magnetometer survey of 15Mm139 for the Kentucky Transportation Cabinet, May, 2001.
Magnetometer survey of 15Gd44, Garrard County, Kentucky, for Cultural Horizons, Inc. and Kentucky Transportation Cabinet, May, 2001.
Conductivity survey at Hopeton Earthworks, Chillicothe, Ohio, for the National Park Service Workshop in Remote Sensing, May, 2001.
Magnetometer survey in the Kituhwa Historic District for the Eastern Band of the Cherokee Nation, May, 2001
Magnetometer survey in Marion County, for Kentucky Transportation Cabinet, April, 2001.
Magnetometer survey in Laurel County, Kentucky, for Kentucky Transportation Cabinet, March, 2001.
Magnetometer survey at Civil War Camp Dick Robinson, Garrard County, Kentucky, for Kentucky Transportation Cabinet, March, 2001.
Magnetometer survey of the Richardson Cemetery, Kenton County, Kentucky, for Cultural Horizons, Inc., and Kentucky Transportation Cabinet, February, 2001.
Magnetometer survey of two historic sites on Paris Pike, Fayette County, Kentucky, for Kentucky Transportation Cabinet, January, 2001.
2000
Magnetometer and conductivity survey at Pickawillany, Ohio, for Cultural Horizons, Inc. and the Ohio Historical Society, November, 2000.
Conductivity survey of possible toxic waste dump, for Kentucky Transportation Cabinet, July, 2000.
Magnetometer survey at Millstone Bluff, Illinois, for Center for Archaeological Investigations, Southern Illinois University, April, 2000.
Magnetometer and conductivity survey at Little Spanish Fort, Mississippi, for Dr. Edwin Jackson, Mississippi Southern University, November, 1999.
Magnetometer and conductivity survey at Mound R, Moundville State Park, Alabama, November, 1999.
Magnetometer survey of four cemeteries at Land Between the Lakes, Kentucky, August, 1999.
Magnetometer survey at Higbee Tavern, for Kentucky Transportation Cabinet, May, 1999.
Magnetometer and conductivity survey at Pinson Mounds, Tennessee, for Pinson Mounds State Park and Dr. Kevin Smith, Central Tennessee State, May, 1999.
Magnetometer survey on the grounds of Whitehall State Shrine, Madison County, Kentucky, for Commonwealth of Kentucky, Division of Parks, April, 1999.
Magnetometer survey at the Broaddus site, Madison County, Kentucky, for Dr. Kelli Carmean, Eastern State University, April, 1999.
Magnetometer survey of two parcels along River Road, Louisville, Kentucky, for Kentucky Transportation Cabinet, March, 1999.
Magnetometer and conductivity survey of two urban sites for Gray and Pape, Cincinnati, Ohio, March, 1999.
Magnetometer and conductivity cemetery at the Rudy Cemetery, Louisville Kentucky, for Kentucky Transportation Cabinet, March, 1999.
Magnetometer survey at Raven Run Park, Fayette County, Kentucky, for Lexington-Fayette County Division of Parks, February, 1999.
1998
Magnetometer survey of site on Paris Pike, Bourbon County, Kentucky, for Kentucky Transportation Cabinet, December, 1998.
Magnetometer survey of the VanBibber Cemetery, Marmet, West Virginia, for Corps of Engineers, Huntington District, December, 1998.
Magnetometer survey of the community of Monterey, for Kentucky Transportation Cabinet, June, 1998.
Magnetometer and conductivity survey at Stubbs Earthwork, near Cincinnati, Ohio, for Dr. Frank Cowan, Cincinnati Museum of Natural History, April, 1998.
Magnetometer survey at Highbank Earthworks, Chillicothe, Ohio, for Dr. N'Omi Greber, Cleveland Museum of Natural History, April, 1998.
Magnetometer survey at two sites at Caesar's Palace, Indiana, April, 1998.
Conductivity survey at 15Wh165, Whitley County, Kentucky, January, 1998.
1997
Conductivity survey at the Peters Site, near Columbus, Ohio, for ASC, Inc, November, 1997.
Conductivity survey at the Hollywood site, Mississippi (continuing), with Dr. Jay Johnson, University of Mississippi and Mr. Rich Stallings, Cultural Horizons, Inc.
1996
Conductivity survey of a historic barn location, Locust Grove Plantation, Jefferson County, Kentucky, for Locust Grove Plantation, September, 1996
Conductivity and Magnetic Susceptibility at Wickliffe Mounds, July, l996.
Magnetic susceptibility at the Millstone Bluff site, Illinois (continuing), with Dr. Brian Butler, Southern Illinois Center for Archaeological Investigations.
Conductivity Survey at the Albert Sydney Johnston Birthplace, Washington, Kentucky, for Cultural Horizons, Inc., March, l996.
Phase II Archaeological Testing within the Jefferson Barracks National Register District and Site 23SL656, St. Louis County, Missouri, Steve Titus, Jim Snyder, and Neal Trubowitz, with contributions by R. Berle Clay and Terrance Martin, American Resources Group, Ltd., Cultural Resources Management Report No. 288.
1995
Conductivity and Magnetic Susceptibility of the Monterey Locality, August, 1995, for Cultural Horizons, Inc.
Conductivity survey of 23SL656. The Jefferson Barracks National Register District, Missouri Air National Guard Facility, St. Louis County, Missouri, for American Resources Group, Inc., Carbondale, Illinois, July 21, 1995.
Conductivity survey of a cemetery near Breeding, Kentucky, for Cultural Resource Analysts, Inc., July 6, 1995.
Conductivity survey at High Bank Earthwork, near Chillocothe, Ohio, with Dr. N'Omi Greber, Cleveland Museum of Natural History, April 18, 19, 1995.
Conductivity survey at the Overly Tract and the Hopeton Earthworks June 19 - 21, 1995, for the National Park Service, Hopewell National Monument.
1994
Historic pioneer station study, Conductivity survey, in cooperation with Nancy O'Malley, Program for Cultural Resource Assessment, University of Kentucky.
An Introduction to the Archaeology of Civil War Battles in Kentucky, for the Kentucky Heritage Council, 87 pp., Frankfort, Kentucky.
1993
1993 Conductivity survey at Zollicoffer Park, Mill Springs Battlefield, Nancy, Kentucky, for Mill Springs Battlefield Commission, Oct. 1, 1993.
1991 - 1992
Conductivity at Perryville Battlefield State Park and Issac Shelby family cemetery, Kentucky, work in conjunction with the Kentucky Division of Parks.
Geophysical Survey: Additional Information
Introduction
Since 1987, CRA has routinely incorporated near-surface geophysical techniques in its own cultural resource management projects and has offered these services to clients. CRA owns state-of-the art equipment including duplexed Geoscan FM256 gradiometers; a Geonics, Ltd. EM38 electromagnetic (conductivity) meter; a TR Systems, Ltd. TR/CIA twin-probe resistivity meter; and a Geophysical Survey Systems Incorporated SIR-3000 Ground Penetrating Radar (GPR) equipped with a 400 MHz center frequency antenna and survey cart. Results are processed using a variety of software, importantly Geoplot, RADAN 6, Snuffler, and Surfer, and results are prepared for our clients using Didger, ArcGIS, and AutoCad.
At CRA we stress the use of multiple survey techniques to gain maximum information in a cost efficient manner. Using high speed, high-density data collecting field equipment and up-to-date processing software, we have a continuing commitment to increasing the utility and accuracy of geophysical survey data in both cultural resource management (CRM) projects and non-CRM archaeological research.
Russ Quick conducting a GPR survey
Berle Clay conducting a magnetometer survey
Applicability of Geophysical Surveys
The survey techniques used at CRA are applicable to a wide variety of sites and variable site conditions. We are dedicated to providing service to the fast-paced world of CRM. The "ideal" survey site would be a manicured lawn with no ornamental plantings, buildings, or any other above-ground obstructions. We have yet to survey such a site. The techniques we use are applicable to open woodlands, provided there is no undergrowth or the undergrowth can be removed, various types of pastures (mowed and standing), crop stubble, and tilled fields. The rule of thumb is that if the site can be walked at a speed of approximately one meter per second without major obstacles (like downed trees and low hanging tree limbs), it can be surveyed. With proper planning, even sites with obstacles can be surveyed; however, obstacles that impede movement, changing the walking pace, or cause the operator to vary the orientation of the carried instrument can introduce noise into the data and making it difficult to interpret.
Fresh agricultural tilling (plowing and disking) does modify the distribution of resistive, magnetic and conductive constituents in the soil and this disturbance is reflected as cultivation or crop "marks" when such fields are surveyed. These tend to become less prominent over the months as the topsoil "stabilizes and homogenizes" due to weathering. Geophysical survey does tend to record the effects of agriculture long after a field has been fallowed, though. We regard these crop striations not simply as noise, but as an important record of modern impacts to a site. Nevertheless, in designing field strategies that will involve geophysical survey, we recommend that surface scarification (for example to facilitate controlled surface collecting) not be used, at least until the geophysical surveys have been completed. Strip plowing should be avoided.
Speaking from our mid-America experience, geophysical surveys may be conducted at all times of the year. We have encountered most problems with extreme heat, but we use specific techniques to control the effects of heat that can cause sensitive electronic equipment to drift, affecting the quality of the data. For best results, the ground should be dry underfoot so that the operator does not collect mud while walking, which can distort magnetic readings in certain types of soils. Electromagnetic surveys, while they are affected by total soil moisture (importantly, a heavy rain during an EM survey can shift the measurement of earth conductivity significantly), appear to be far less susceptible to total soil moisture than soil resistivity surveys that tend to be unproductive when the soil is either saturated or extremely dry.
The techniques we use that involve magnetics have circumscribed utility in urban contexts with a record of building, demolition, and rebuilding. The problem is metal targets of all sorts. The random metal target produces a major disturbance of the magnetic field surrounding it, at least as it is recorded by a magnetometer or a earth conductivity meter. This obscures the weaker signals that reflect the archaeological targets that we seek (like burned posts, hearths, house floors, etc.). Soil resistivity and GPR can be still be used in these areas.
3D image showing graves that CRA identified with Ground Penetrating Radar (GPR)
After considerable field experience with the site type, we have concluded that near surface geophysical surveying techniques of all types can be useful for defining historic cemeteries. There are exceptions: pioneer era cemeteries that have become overgrown with trees and children’s burials can be difficult to identify. Most geophysical techniques can define a cemetery’s past, enclosed limits, and this knowledge is important in certain CRM situations. In certain situations, geophysical techniques can provide precise locations for individual graves, but this depends a great deal on the age of the cemetery, the soils, and the “standardness” of the graves. Not every technique works well for delimiting cemeteries. This becomes glaringly apparent when a historic cemetery is excavated as part of its relocation (a practice which we find is becoming increasingly important in CRM archaeology). The reasons for this seem to be that the act of historical burial is a very "brief" geophysical episode and, depending on soil type and grave depth, one that generally causes minimal geophysical modification of the soil or, as in the case of agricultural tillage, modification that is erased with weathering over time. However, the use of multiple, complimentary geophysical techniques (e.g. magnetometry and GPR) often produces a more accurate record of a cemetery than simply probing the soil.
A Note on Research Design
Since they involve intensive ground coverage, the near-surface geophysical survey techniques we use are generally not cost effective in phase I, site discovery surveys. They have an obvious place in phase II, site evaluation. Integrated as the "leading edge" of a phase II evaluation which may involve intensive shovel testing, excavated units, and surface scrapes, they provide a wealth of data that can be used to inform the traditional field techniques which follow in the evaluation. Geophysical surveys never replace conventional data collecting techniques. They can significantly reduce the cost of phase II evaluation by, for example, eliminating area disking and controlled surface collection, which is labor and time intensive and, to the extent that they aid in a better definition of site parameters, lead to both better evaluations of significance and, in the case of a National Register of Historic Places eligible site, cost effective, informed mitigation plans. Often as not, geophysical techniques are used to inform archaeologists where not to dig to achieve the best results during a survey!
Field Protocols (how we collect data)
CRA uses magnetic gradient, electrical resistivity, GPR, and earth conductivity survey techniques that have proven applicability to a wide range of survey conditions and all seasons. Normally, geophysical survey data are collected on CRA projects in 20-m squares and the average survey time for a square is 20–25 minutes. Within a square, readings are taken at measured intervals along transects typically spaced .5–1 meter apart for a total of 1,600–3,200 readings per 20-m square. With both the magnetometers and the earth conductivity meter, readings are routinely taken at 12.5-cm intervals. The GPR routinely takes readings at 2-cm intervals in the horizontal direction with 512–1,024 samples in the vertical direction, vastly increasing the number of readings without appreciably increasing survey time.
Grids are marked with non-magnetic materials, typically plastic pin flags. CRA has found that a major source of "noise" in magnetic and electromagnetic surveys is wire pin flags used by archaeologists in early stages of their field research. We recommend that plastic flags or wooden stakes replace wire pin flags if geophysical survey is contemplated at any future point in the research program at a given site. It is advantageous to remove “field metal” (e.g. horseshoes, bits of farm equipment, etc…) from the site during the field walking stage for the same reasons.
Geophysics Links
Geophysics Publications by CRA Staff
* This report is in pdf format (size: 729kb). Another browser window will open.
* This report is in pdf format (size: 0.97 MB). Another browser window will open.
Geophysics Project Examples by CRA
2012
2011
2010
2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1991 - 1992