Earth Surface Effects in Ground-Penetrating Radar Responses
Bibliographic record
Abstract
Ground penetrating radar (GPR) surveys are often performed with transmitting and receiving antennas close to each other and placed close to or on the ground surface. Groundcoupled transmitting antennas couple better to the subsurface than air-coupled antennas. Especially the wave field traveling in the subsurface between the surface and the critical angle is very strong compared with the field transmitted into the ground when an antenna is air-coupled. A similar effect occurs at the receiving antenna. The direct air wave traveling along the surface transmits a wave that propagates into the ground along the direction of the critical angle, namely the head wave. This implies that shallow subsurface scatterers can be present in the data with a move out corresponding to the velocity of the wave in air. The direct ground wave has an evanescent part in the air that propagates along with it with the ground velocity. This implies that above surface objects not only scatter from the direct air wave but also, from the direct ground wave. These scattered waves can be present in the data with a move out of the velocity in the ground. Examples such as vertical posts, rods, metal fences that have a large electric contrast with their surroundings, produce responses that are in some cases recorded by the receiving antennas, the so-called “phantom” subsurface targets. The recorded responses show source-target-receiver distance and orientation dependent time move outs that correspond to waves travelling in air or waves travelling through the ground. These are understood in a clearer manner from the radiation patterns. The electric field generated on the ground surface by a horizontal electric dipole placed just above the ground surface has an air wave radiation pattern that is similar to that of an electric dipole in free space, but the ground wave has an almost omnidirectional radiation pattern. This implies that for parallel antennas the direct air wave can be minimised in the data by choosing a suitable azimuthal angle between the transmitter and receiver antennas.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.005 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".