by Lawrence B. Conyers and Denisse Argote
GPR mapping to reconstruct a Late Classic Period Compound Wall, Chichen Itza, Mexico
by Lawrence Conyers and Denisse Argote | Integrating a lidar relief map with GPR subsurface mapping, accompanied by locating known and inferred surface structures allowed for the reconstruction of a Late Classic Period walled compound. It was found that this enclosure is not perfectly rectangular, was partially dismanteled in the past, added on to in…
5 responses to “GPR mapping to reconstruct a Late Classic Period Compound Wall, Chichen Itza, Mexico”
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Hi everyone. Larry here. I am writing this comment in the hope that I can get others to make comments after looking at this, and other articles here. So far there has been limited numbers of people who feel like they want or can comment. I know subscribers have been reading the articles, as I can track the downloads (not actual reads) and there have been more than 80 on the Laetoli article, and in the 20s or 30s for the other articles. I am not sure why there is a lack of comments. Perhaps people are just more familiar with doing “thumbs up” or “likes” on social media? Will you please make even a short comment about the articles after you have read them? And perhaps we can get a different kind of a discussion going, which is different than with most articles that I or you have published, which just go into a “black hole”. Thanks.
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Had to read this one since the amazing Denisse was also involved! Fun read and interesting project. I have a technical question for the two of you though. The paper states, “Profiles were collected in both x and y, with the 400 MHz data collected in x and the 900 MHz in y.’ What is the advantage of this method over collecting both instruments in the same direction? Or what was the plan/reasoning, if there was any? Just curious if it this was intentional design for a particular reason, or due to lack of time, funding, etc.? Thanks!
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Thanks Tamara for the comment. I collected one day with the 900 MHz, and it got hot and we quit to go to the pool to swim! And have a beer. The next day Denisse collected with the 400 MHz and went the other way, and we called it quits for the same reason. No reason whatever for not going both ways with both antennas, other than we just didn’t have the time. But this turned out to be a good idea to have both x and y profiles, as the wall segments that were visible were sometimes only visible when the profiles crossed them at a right angle. So our placement of the walls was enhanced by having both sets of profiles.
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This is a neat project. In Figure 9, what is the association between the “stacked” planar reflection interpreted as the wall segment and the broader upward sloping planar reflection that begins at 30 ns in twtt and 14 meters along the profile, and extends to ~ 20ns in twtt and 32 meters in the distance range? Since the reflector varies in depth, it can’t be a “gain artifact” from the manual adjustment of the gain curve, which would gain all samples at the same depth, right? It looks like the annotated profile is from the 400Mhz antenna while the slice maps are generated from the 900Mhz data. Are the wall features visible in the profiles of the 900Mhz data as well? Do they look the same? Also, any thoughts on the feature visible in the top center of your grid in the Lidar image? It looks like it also shows up in the amplitude slice maps with the center coordinates at approximately x = 22, y = 45. Is this an additional structure? Great paper and what a privilege to get to work at such a notable site.
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Thanks Brandon. Very intuitive of you. My annotated wall locations are placed on the 900 MHz slice map. I made the same map with the 400 data, and it was just not detailed enough. It really doesn’t matter much, as both frequency slice-maps are showing rubble, and neither can “flesh out” the actual walls. ONLY by interpreting the 2-D are the walls visible. That is the reason I posted this report in the first place. To try to get people to realize that amplitude maps are not the way to go, but only a first step. And all “real” interpretation comes from integration of slice-maps and profiles. That other feature you see is one I am working on. It kind of lines up with that corbel arch that I noted. It is flat topped and wide. One idea of Denisse’s is that it is a Sacbeob, which is a raised roadway or path made with stone retaining walls and filled with earth and rubble. More work is needed on that, and I am curious if it continues to the east toward the Caracol, where we might pick it up again…
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