There are many practitioners who can use the wonderful software we have for GPR to produce some very fun and sometimes important images of datasets. Most users can do this these days. My goal is to interpret those images to make the most comprehensive interpretations possible using all the data available.
What is below the surface? To understand how radar waves move and reflect in the ground under various conditions, we must first understand these robust datasets both geologically and archaeologically.
To do this I usually start with the smallest dimension (the individual reflections with GPR) such as this one trace:
and then move to images of many reflections in 2-D profiles
and finally to maps of the relative amplitudes to understand the ground in 3-D .
All these datasets need to be evaulated individually, and merged to produce an overall understanding of what is buried below the surface. In this process additional data processing may be called for such as frequency filtering, migration and topographic adjustments. The goal is to move deliberately through these steps in order to understand what in the ground is producing what types of reflected waves.
- This is different than what many practicioners (and those who write software) often propound. They often bypass the data analysis steps to go directly to final products, which are 3-D maps of amplitudes (also called slice-maps by some). When the intermediate steps are bypassed, much of the important information about the ground is lost, producing less-robust results.
Some notes on my history with GPR:
- I began working with GPR in the late 1980s before we had digital systems, or any software to speak of. All I was able to use some very “clunky” softweare based in DOS (anyone remember command files and executable files?) first. I came to GPR from the reflection seismic world, having worked in petroleum exploration for 15 years so was used to this kind of “painful” data processing.
- My PhD dissertation was using GPR on a Mayan site in El Salvador (Ceren), which was the first research of its kind to integrate GPR with archaeological and geological information. In that process I had to convert analog data (recorded as nothing but voltage changes on audio tapes!) into digital data to produce 2-D images. Today we are fortunate not to have to go through these laborious steps.
- I spent 28 years as a professor at University of Denver (1995-2023), where I spent a good deal of time training graduate students and writing many articles and books.
- During that time I also did much consulting work and worked on research projects on every inhabited continent. Some years ago I counted up all those projects, and ran out of patience after reaching 980. Results from many of those surveys are in my books and articles.
- Also during that time I was the team leader in developing software, which is still used by many GPR workers around the world. That sofware is free to download. Write me back if you have any questions and I will consult with you on your work, if you wish.
- Presently I am working on these projects:
- GPR mapping of hominid footprints at Laetoli, Tanzania. Some results are presented here.
- GPR at Chichen Itza, Mexico concentrating on the late Classic landscape prior to the construction of the Postclassic monumental architecture. Working here with the Instituto Nacional de Antropologia e Historia, Mexico.
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- Preparing for the annual Advanced GPR Interpretation Workshop, which has 26 people registered for this coming winter.
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- My goals for the future:
- Work on projects where I am invited to participate, and where I can use my skills and experience in new and interesting ventures.
- Continue to train GPR enthusiasts, so they can develop skills to help them in their careers. In this process I hope to continue to build a GPR cohort of certified GPR users who have completed my very rigorous workshops, held every winter on-line.
- See if I still have any influence with the more youthful GPR people out there, as this article in Wired Magazine discusses.
Some thought on the history of GPR in archaeology and the future