The maximum depth can remote sensing data explore is just 40 cm directly. The other subsurface information can be deduced indirectly and using integration method of field survey and remote sensing data.

Remote sensing can be used a good technique for knowing subsurface information in many scientific area.

Dr. Prasad, I also hold the view that Remote Sensing cannot be a replacement to field investigations. Nothing can compare to human investigators! Optical (VIS, NIR, TIR) and SAR remote sensing techniques cannot sense/penetrate more than a few micrometers to less than a meter of the earth's surface. It also depends on the kind of material something is made of. However, one might argue in the strictest sense of the definition, even geophysical instruments such as Ground Penetrating Radar (GPR) and acoustic instruments such as SONAR etc. may fall in the category of remote sensing. If that be the case then it is true that these instruments have the ability to penetrate 10's of meters into the earth's surface. Having said that, I would like to point out that remote sensing has its unique advantage. It provides a different perspective unlike insitu measurements. Obviously one would not go around doing field investigations on a country or a continental scale if remote sensing can do better part of the job. To cite an extreme example, look at one of the greatest machines which humans have built - Curiosity Rover. I can only marvel in awe how humans have been operating this machine remotely 225 million kms away from Mars for the past 5 years. So, although human field investigation is crucial in itself, remote sensing sometimes takes precedence. These are only a few reasons why we need remote sensing.

For the examples that you have mentioned, I believe field investigations are indispensable part of the research. In any case, I would support both kinds of investigations into a research.

https://www.youtube.com/watch?v=fKVPFyu_tHQ

Here is a relatively new article from MIT.

It's about a new means of navigation for

cars, seeing below the surface with radar.

http://news.mit.edu/2017/lincoln-laboratory-enters-licensing-agreement-to-produce-localizing-ground-penetrating-radar-0718

Other:

https://download.bgr.de/bgr/aerogeophysik/Berichte/Technischer-Bericht-111-Ellerbeker-Rinne-Web.pdf

https://www.researchgate.net/publication/282500385_A_review_of_helicopter-borne_electromagnetic_method_for_groundwater_exploration

https://www.scientificamerican.com/article/radio-waves-locate-water/

https://www.newscientist.com/blogs/shortsharpscience/2011/02/new-map-shows-the-leaks-in-our.html

https://phys.org/news/2017-04-reveals-sources.html

Regards,

Joachim

Article A review of helicopter-borne electromagnetic method for grou...

Modern remote sensing technique can decipher information upto 10 m from ground level.

Time variable gravity field observations from the Gravity  Recovery and Climate Experiment (GRACE) satellite mission provide an opportunity to estimate water storage changes in the Earth's terrestrial column. Several studies have combined it with outputs from hydrological models to study groundwater rates, aquifers and  terrestrial water changes.  Though not typical of optical remote sensing systems, the GRACE mission uses a satellite to satellite tracking system to infer these changes (Earth's gravity field), which are mostly the result of mass redistribution of water and other dynamic processes, e.g., post glacial rebound. It remains one of the biggest and mind-blowing achievements of satellite geodetic investments. This makes remote sensing super interesting and perhaps the only way out for humanity to fully and easily understand changes in the hydrological cycle.

https://gracefo.jpl.nasa.gov/science/water-storage/

Dear Experts thank you for your answers.

From some of the answers it appears that my question has been misread. I am not at all questioning the utility or usefulness of remote sensing technique, as far as spatial information is concerned. I am only asking the extent of its application with reference to "DEPTH" below ground level (like 50 cm; 100cm; etc); the information one can decipher (temperature, moisture, etc); and also the type of data sets one has to refer.

Kindly do not compare / mix up with geophysical techniques, which may confuse the readers. Thank you. 

Dr. N. B. Narasimha Prasad  - I seen this question today and felt to state my understanding:  

Remote sensing (RS) is the best technique to obtain information of the earth surface features. The main advantage of this technique is the capture of data covering large and inaccessible areas within short time, which is not possible by the conventional methods (field studies).  

The information on subsurface features can be derived directly from RS only up to a depth of few centimeters.

But, indirectly, RS integrating with GIS  can provide information on subsurface features, for example delineation of groundwater potential zones. RS (satellite image) provides quick and useful baseline information about the factors controlling the occurrence and movement of groundwater like geology, lithology/structure, lineaments, geomorphology, soils, landuse/landcover, drainage pattern etc. The conventional methods do not always take into account the diverse factors that control the occurrence and movement of groundwater. But the findings from RS/GIS should be verified before putting the confirmatory well. 

In the field of earth sciences, the application of RS is getting recognition in mineral exploration, delineation of groundwater potentials, and in understanding the scale of geohazards and other geoenvironmental issues.

- Regards

Thanks for your efforts to answer. Here the main information sought was what is the maximum depth to which one can get the sub-surface information using RS.

The following attachments on RS may interest you.

This question on the effective maximum depth of penetration was not given any definite answer. I have a knowledge that depth of penetration of this; though useful investigation tool, is shallow (unknown range). Can the experts in the field of remote sensing come up with an authoritative answer or clue? Thanks.

In soil science studies, especially classification, the soil is affected by geomorphological factors, climate, parent materials, etc., and it is different in each region, and without field studies and sampling, it is not possible to make an opinion. How can remote sensing determine nitrogen, texture, structure, classification, layers and horizons of soil and.... In order to do the work correctly in field studies, the presence of experienced experts is essential