Ashley and Leah collect data with the 225 MHz antennae.

What is GPR?

Ground Penetrating Radar (GPR) is based on the propogration of high frequency electromagnetic (EM) waves into the ground and measuring the repsonse as they are reflected back to the surface. EM waves respond to the electric conductivity and the magnetic permeability of the material through which they are traveling and once these conditions change, the waves are reflected back to the surface. After these waves are reflected the travel time is measured and an image is produced which can be seen on a portable computer for immediate interpretation in the field.The post-acquisition analysis involved processing and plotting the information using pulseEKKO software and interpreting the data sets with radar stratigraphic analysis.

 

GPR on Hapuna

Several GPR lines were collected on Hapuna Beach. Our goal was to look at the subsurface stratigraphy and interpret the data to see if the beach is eroding.

Problems

Saltwater is a very conductive material which atennuates the GPR signal. Therefore collecting GPR data in areas where saltwater intrusion is present, is extremely difficult. This was the case at Hapuna Beach. There were some areas however farther away from the ocean/beach interface where freshwater dominated and we were able to see a few meters in the subsurface.

 

Example Profile

Preliminary plotting of one of the GPR lines taken at Hapuna.