Dharmasthala Crimes: SIT likely to use GPR technology to find skeletal remains

Bengaluru 

The Special Investigation Team (SIT) probing the Dharmasthala mass burial case is likely to use Ground Penetrating Radars (GPR) to find out the presence of skeletal remains. The SIT that has completed digging in ten spots and will commencing the investigation from 11th on Monday.

One of the advocates, Manjunath N, on Sunday (August 3) issued a press release demanding use of the GPR as the SIT is grappling to find the bones in the the places identified by witness-complainant. 

A highly placed source in the SIT talking to blrpost.com said “I think we would be needing the GPR for the remaining spots or for the 13th spot.” The GPR is good at finding cavities but not that effective in finding bones. It should be noted that SIT Chief , Pronab Mohanty used this technology somewhere at India-Pakistan border when serving in the Border Security Force (BSF). This means the technology is no alien to him. 

It is interesting to see whether this technology will be utilised for all the remaining spots or only for 13. The SIT after completion of 13 spots may also look into 14 and 15 spots. It should be noted that the SIT is officially maintaining that they found one skeletal remains in the 6th spot including the skull. 

GPR technology

Choosing the correct Ground Penetrating Radar (GPR) frequency is crucial for effective subsurface investigations. Lower frequencies, typically in the range of 50 to 200 MHz, can penetrate deeper into the ground—reaching depths of 10 to 15 meters under favorable soil conditions. However, these frequencies provide lower resolution, meaning they cannot clearly detect small or detailed features. In contrast, higher frequencies ranging from 400 MHz to 1.5 GHz offer much finer detail but are limited to shallow depths, generally up to about 1 meter. This is according to an article published on India.com. 

In cases where targets such as buried bodies may be located at various depths, a combination of frequencies is ideal. Alternatively, specialised low-profile antennas that remain close to the ground can be used. These antennas reduce interference and enhance signal clarity, improving the chances of detecting both deep and shallow anomalies.

Soil conditions near the Netravati river

The soil near the Netravathi River consists of alluvial deposits, including a mix of sand, clay, and silt. Due to frequent and heavy rainfall, the ground remains moist and contains mineral components such as hornblende and kaolinite. Moist or clay-rich soils are known to absorb and scatter radar signals, which can reduce the effective depth of GPR penetration, the article noted.

Despite these challenges, GPR is still capable of detecting variations in the soil’s electrical properties and moisture content. When a body is buried, it alters the natural layering of the soil. Over time, decomposition can lead to voids, changes in moisture, and differences in soil density—these disturbances appear as distinctive patterns, such as hyperbolas, on GPR scans.

When performed during dry weather conditions and handled by experienced operators, GPR surveys can produce reliable results even in challenging environments like the Netravathi region. Compared to manual excavation, GPR offers a faster, less invasive, and more comprehensive method for identifying potential burial sites.

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