Subsurface Imaging in Archaeology- Geology 495
aka: Archaeological Geophysics
Professor: Steve Sheriff
Syllabus, the ad, project reports, grading papers
Excel tips & exercises (free!)

Spring Semester, 2009:

1/27/2009: Intro to course, and a basic discussion on geophysical targets and methods (magnetic, gravity, electrical, radar). The latter lead to three basic questions: 1) what are you looking for?, 2) what are the physical characteristics?, and 3) what are the material contrasts?, and a flow chart for the experimental process. Introduction to gravity, gravity units, gravity over a buried sphere, my notes.

2/3/2009: More gravity: buried sphere and horizontal cylinders (spreadsheet example), latitude and elevation corrections, drift curves, field methods, operation of the Scintrex CG3 gravity meter, and an abstract of an archaeological study using gravity. Berkeley's gravity page, and my notes.

Using CSM Java applet for modeling the gravity anomaly (another from Berkeley) over a tunnel and an assignment.

2/10/2009: Discussion of our gravity measurements (error and estimates) and your bids. Introduction to DC electrical resistivity (Loke's tutorial <-6 megs!, analog model , example). The apparent resistivity of subsurface materials is measured with a number of common arrays used both for profiling and sounding. My notes.

Assignment: find a professional paper using gravity or DC resistivity pertinent to your interests in archaeology or geology - be prepared to give us a short review of that paper next week (Authors, problem, experiment, results). We'll use these presentations as a basis for furthering understanding and answering questions.

2/17/2009: Discussion - the papers you read. The Syscal kid specs, depth of investigation and case studies (Coloma (figure, paper), Sandhill, (ppt), Coloma data), and a web report. Modeling with readily available software demonstrates:

1. variations of resistivity in the subsurface cause different apparent resistivity values at the surface
2. arrays have variable sensitivity (Wenner, dipole-dipole).

2/24/2009: Plotting pseudosections. Two programs, RES2DMOD and RES2DINV for modeling and inverting electrical resistivity profiles, with some data to invert. Self assessment assignment: read this paper on grave detection using resistivity. The Schonstedt fluxgate magnetometer and Earth's magnetic field (declination, inclination, magnetic elements).

3/3: Geomagnetism, (D, I - Missoula), magnetic exploration, Schmidt (2007). Flux around a dipole, buried dipole applet (block model). Magnetic minerals and rock magnetism (Butler chapter 2, 3); my notes.

3/10: Gridding, contouring and a start to interpreting magnetic data using Magpick (source) and upward continuation (my notes).

Lab Exercises in CHC 11 - 82497:

1. make a folder on the desktop with your name on it
2. download the data (epwr.dat, epwr_sparse.dat,epwr_sparser.dat) into your folder
3. start Surfer: grid epwr.dat at 0.5 meter spacing and save it in your folder
4. make a contour map, and overlay a post map of actual data locations. Do the same with the two more sparsely sampled grids. Now, look at and think about your results - what do they tell you about sampling and gridding?
5. experiment enough that you are comfortable with Surfer, maps, and results (grid at different intervals, try different map types)
6. Use Magpick and remove and experiment with upward continuation and isolating equivalent sources from various depths.

3/17: Take home Exam due 3/24. Data acquisition & equipment demo with:

• The Syscal Kid Switch 24 (see information sheets). The hitch in downloading was because I did not specify new 'directory' before 'new filename' when we acquired data. So our data were stored concatenated with the last new file I had used, SANDHIL, rather than stored as file 1 and file 2 as I thought I'd named them. Note that in the manual, 'directory' means 'file'. here they are (wenner, dipole-dipole, brief results) we'll look at them next week and I will go over the download bit again (successfully).

• The Geometrics Cesium Vapor Magnetometer (the manual, the theory). This paper, from Gem Systems Inc., provides an excellent overview of understanding magnetic maps - check out their case histories in archaeology. These figures (1, 2) provide a visual orientation to the way the sensor of the Cesium magnetometer must be oriented; you figure that out with Geometric's program: CSAZ.
  
  Here are the simple steps (and condensed operating notes and the manual):
  1. Get a key for CHCB 3 from Loreene in CHC 311 - you are now responsible!
  2. Take the magnetometer to the field and lay out a N-S rectangular grid
  3. Assemble the magnetometer, power up, select "Simple Survey" and an unused file number (or delete existing files).
  4. Hit"Mark" to start each line and at designated midpoints, use End Of Line at line's end.
  5. Hit ESC (any key really), then Mark to start the next line, End of Line at the end
  6. The sequence as you acquire successive lines is MARK, MARK...,EOL, ESC, MARK, MARK,..., EOL
  7. ESC back to the main menu when you are done and power the instrument down
  8. Back in the lab, put the battery on the charger.

3/24: Exam review (brief); data acquisition (base stations, layout, space weather) and field methods continues. We acquired more resistivity data (1, 2) and magnetic data (1, 2)

3/31: Spring Break!

4/7: We'll discuss developing individual field assignments. I want a project with either the gravity meter, magnetometer, or electrical resistivity equipment. Here's your assignment for next week:

I want a 2-3 page (not including any figures/references) proposal of your project. Your proposal should include:

• brief introduction with a concise description of the problem to be solved
• description of your proposed survey based on the problem to be solved and why your experiment is the correct choice
• description/explanation of your proposed procedures
• summary of possible problems/limitations of the surveys
• statement of why your proposed experiments will be successful
• description of the project report you intend to submit on completion (nature of data, figures and graphs) as if you were bidding for a contract.

Intro to GPR; Dielectric values, water & velocity, velocity, RDP, wavelength, frequency, reflection coefficient, multiples, metal 'ringing', and diffraction hyperbolas (graves).

4/14: Discuss your proposals: footprint, resolution(2, 3), downloading (measured frequencies: 50mhz, 100mhz, 500mhz), coupling, and experimental design; GroundVision demo (2008-files). My GPR notes (1, 2, 3).

4/21: Mala Ramac (their applications) GPR in the field: setup and operation. Here are the GPR data, numbered 101-114 for your processing assignment. ProsysII, for downloading resistivity data, is installed on the laptop, as is GroundVision, Magmap2000, Magpick, and Surfer.

4/28: Review your Groundvision results; processing GPR data with Reflex, example.ppt (animate: 1, 2). Assignment: Read a GPR (or other application) paper and be ready with a 5-10 minute presentation/discussion as we did earlier in the semester (authors, problem, experiment, results).

5/5: MYAP ppt., your presentations, processing, discussions, etc.

5/12: Final Exam 1:10 - 3:10, Tuesday, May 12, CHCB 333.

Relevant Links:

Relevant terms - supply and learn the definitions	Intro & Perspective	GPR Basics EPA
Gem Systems - Understanding Magnetic Maps (3 mb)	Radar and Archaeology	The 2007 course
Equipment Setup and Use	NOAA Geomagnetism	The 2008 course
Archaeo-magnetics, Smekalova et al., (16 mb!)	My handouts and Tips

Relevant Journals:

Archaeological Prospection - informs archaeologists, environmental scientists, site developers, local authorities and regional environmental agencies about the wide range of scientific techniques available for the study of the near-surface environment.

Journal of Archaeological Science - is aimed at archaeologists and scientists with particular interests in advances in the application of scientific techniques and methodologies to all areas of archaeology.

Near Surface Geophysics - an international journal for the publication of research and development in geophysics applied to the near surface. It puts emphasis on geological, hydrogeological, geotechnical, environmental, engineering, mining, archaeological and other applications of geophysics as well as on physical soil and rock properties.

Geoarchaeology - an interdisciplinary journal which presents the results of original research at the methodological and theoretical interface between archaeology and the geosciences.

SAGEEP - The Environmental and Engineering Geophysical Society (EEGS) convenes the annual Symposium on the Application of Geophysics to Engineering and Environmental Problems (SAGEEP). Proceedings (and the journal) sometimes have archaeolgical papers.

Quick comments on some texts:

Handbook Of Geophysics In Archaeology, A.J. Witten, Equinox Handbooks in Anthropological Archaeology, 2006, 343 p. This is a good, informative and readable introductory text. The organization is excellent as is the breadth of topics and case studies. It should serve well as a textbook. On the downside there are a few errors in the text, among the most glaring is the consistent use of remnant instead of remanent in the magnetics section; likely an editor's mistake rather than the late author's.

Remote Sensing in Archaeology: An Explicitly North American Perspective, J. K. Johnson ed., Univ. Alabama Press, 2006, 319 p.  This is a set of papers resulting from a meeting. All the major methods are presented and reviewed, often in the context of "cultural resource management". The are lots of good case studies but there is insufficient physical background to make this an informative reference book. Never the less, it is a worthwhile read.

Field Geophysics, John Milsom, Wiley, 2003, 3rd edition, 232 p. This book provides the basics of a large spectrum of techniques. It is not specifically archaeological in approach, but it serves as a useful, handy reference and source of facts.

GPR for Archaeology, L. Conyers, Alta Mira Press, 2004, 203 p., This is an excellent book on a specific technique for archaeology. It is well written and all the necessary background is provided in an easily digestible fashion - recommended.

Magnetometry for Archaeologists, 2008, Aspinall, A., Gaffney, C., and Schmidt, A., Alta Mira Press, 208 p. This book gives a very sound background to understanding of magnetics and why there are magnetic anomalies over many archaeological targets. The applications, data processing and visualization are directed mostly at results and conditions in Britain.

 

 

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