My analysis of the technical content of Biondi's articles :
The two articles :
only differ by their experimental section. Texts and images in the methodology section are almost identical and they were published back to back. They can be analyzed together.
I'll refer to the author as Biondi as comparing the articles it is evident he is the one responsible for the technical content.
Theory
In these articles Biondi use satellite radar data to image subsurface structures.
A common critique of the claim is that radar can't penetrate far underground. This critique doesn't apply to the articles because Biondi is not using the radar data to see directly underground. Biondi is using the radar data to measure surface vibration.
SAR imagery data acquisition is not instantaneous. If the imaged object moves during acquisition, artifacts are introduced in the data. However, the same way you can reconstruct the movement of a light in a long exposure picture, you can extract vibration data from the SAR artifacts. Vibrations cause a small Doppler effect (change in the frequency) that can measured. From this measure the vibrational characteristics can be calculated.
The method uses spotlight mode SAR, this means that while the radar satellite is moving, it rotates in order to keep pointing at the pyramid, creating radar data from multiple angles. The vibrational characteristics of the pyramid is estimated for each viewing angle.
Tomographic reconstructing allow the imaging of the inside of a structure from data measured on the surface at multiple angle. X-ray tomography images the inside of a structure by measuring how much transparent to x-ray it is from multiple angles. Biondi apply this idea to the vibrational data obtained from the SAR data. The result is a SAR Doppler tomography.
The theory is based on previous research works (some of them by Biondi's team). It seems plausible.
Experimental results
Biondi used this tomography technique on two different cases : Mount Vesuvius and the Great Pyramid of Giza / Pyramid of Khnum-Khufu.
As many have remarked, the first step should have been to validate the technique on a know structure. I think Biondi kind of tried to do so with the volcano, but failed in my opinion.
He compares his results to magnetotelluric tomography images :
There are only 2 comparisons, they are visual comparisons without any calculated matching score nor detailed analysis.
One weird thing I noticed is that on the left side comparison high magnitude areas seems to match high resistiviry (resistivity?) areas, while on the right side comparison high magnitude areas seems to match low resistiviry areas.
That's it, that's the whole of the validation against data from other sources. It's very poor, and while the pictures kinda match, that's not really convincing. The images have probably been selected because they are the ones with the best match.
Experimental validation on the pyramid case is even worst.
We have a few comparison between Biondi's results and known structures within the pyramid :
Whole pyramid
Zed
Queen's chamber
There a some structures that match, some that don't. The results show a high level of noise, the matching structure could very well be pareidolia. Biondi doesn't really discuss the quality of the matches.
The most significant comparison to me is the first one. Why is intensity on the left side of the pyramid so much different from the right side? Shouldn't the "shell" of the pyramid have a somewhat uniform density? Is the whole right side a hole? It's a like a third of the pyramid, you can't just ignore it.
A good detection method detects what it's supposed to detect without too many false alarms (low false positive rate). Biondi fails to show that his method detect know structures, but implies that since there are some matches for known structures the rest of what is detected must be unknown structures, without any words about potential false positives.
Conclusion
Although the theory behind the findings is plausible, the experimental protocol and validation are really lackluster, more aligned with trying to prove the methodology works without any reservation than trying to check whether it does and what are its limits.
This is the methodology they used to detect complex structures hundreds of meters underground. From the quality of the results on the example cases, I'm not convinced it could.
I don't think Biondi is acting in bad faith.
Firstly, the method is the result of multiple papers throughout his career, he has submitted a patent application for the technique and it looks to me as if he is planning to sell his analysis services (
https://www.harmonicsar.com). He seems genuinely convinced his method works.
Secondly, the lack of experimental result validation seems to be a recurring feature of his research papers. In
Monitoring of Critical Infrastructures by Micromotion Estimation: The Mosul Dam Destabilization, which our two articles are building onto, his team evaluate vibrational characteristics of a bridge and of the Mosul Dam, without comparing their results to any other data to validate their finding. It's not bad faith, only bad science.