1. GPR Ground Penetrating Radar

2. Ground Penetrating Radar (GPR) is a tool archaeologists will use more and more for excavations in the 21st century. GPR allows archaeologists to survey archaeological sites in a short amount of time with precision and without digging.

3. Basic Principles
Uses radio waves to create picture of underground before excavation
Picture is used to locate any variations in the sub-surfaces

4. Basic Mechanism
Electrode magnetic waves emitted into the ground and time measured for wave to be reflected and received
When wave hits areas of change in soil, it is hit back to receiver antenna
Changes in soil can include objects buried underneath the surface

5. Greater surface difference = Stronger signal
Strong signal has large amplitude
Weak signal has small amplitude
Amplitude wavelength and time are used to create image of what is underground

6. RDP Relative Dielectric Permitivity
“RDP is ability of a material to store and allow passage of electromagnetic energy when a field is imposed upon it.”
RDP of a substance = electrical permitivity / vacuum

7. K = RDP
C = Speed of light
V = Velocity of radar energy

8. GPR Depth Determination
D = (5.9t)/sqrt of (Er)
Dielectric constants for common materials
D = depth of target (in)
t = wave travel time (nanosec)
5.9 = a constant incorporating speed of light and unit conversions
Er = dielectric constant of subsurface material
Air 1
Pure water 81
Fresh water (ice) 4
Granite (dry) 5
Clay (saturated)
8-12
Sand (dry)
4-6
Sand (saturated) 30

9. Example
How deep below the surface is an object that is detected at 46 ns in dry sand (Er = 4)?
Answer:
D = (5.9 x 46) / sqrt (4)
D = in
Therefore the object is about 11 ft underground

10. Equipment Consists of: 1. control unit 2. display unit
3. transmitting and receiving unit

11. Case Studies
Cave of Letters
Bethesaida, Israel
Forum Novum

12. Cave of Letters
Site located in Nahal, Hever (a canyon by the Dead Sea)
GPR was used to map possible excavation sites in the Cave of Letters

13. Artifacts Found Coins Clothes
Letters mentioning Jewish leader Bar-Kokhba who had fought against the Romans around the middle first century

14. Bethesaida, Israel Located in Northern Israel near the sea of Galilee
Was an active fishing community 2000 years ago
Site where Jesus healed a blind man and walked on water

15. Overview Movie

16. Bethsaida Excavation GPR has tested land for cave locations
Artifacts found:
1. coins (dated as far back as 1st and 2nd Century)
2. child’s sandal
3. fabric
4. pottery
5. human bones and remains

17. Antenna Movie

18. Recently, Dr. Harry Jol, professor of geography at the University of Wisconsin - Eau Claire, used GPR to map an area by the city gates of Bethsaida

19. Vescovio, Italy Romaneque church of Santa Maria
Remains of marketplace, living quarters, storage areas, hallways and door entrances reconstructed visually

20. Forum Novum
Remains of marketplace, living quarters, storage areas, hallways and door entrances reconstructed visually
Believed to be Roman marketplace which initially began construction in the 1st century BC and flourished through the 4th century AD as the Roman town of the Forum Novum

21. Excavation
British School of Archaeology in Rome have conducted excavation sites
Sites include:
1. an amphitheatre
2. a bath complex
3. the villa
4. a tomb complex
5. crypts from the 8th to 9th centuries located behind the church

22. GPR reading from Forum Novum

23. Wrap up… GPR usage has become more wide-spread
Now used in construction
Average person can now purchase GPR equipment