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GPR Ground Penetrating Radar

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GPR Ground Penetrating Radar Ground Penetrating Radar (GPR) is a tool archaeologists will use more and more for excavations in the 21st century. – PowerPoint PPT presentation

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Title: GPR Ground Penetrating Radar


1
GPR Ground Penetrating Radar
2
  • Ground Penetrating Radar (GPR) is a tool
    archaeologists willuse 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
RDPRelative 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
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 135.7
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
  • http//www.joeinfo.com/gpr/overview.MOV

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

17
Antenna Movie
  • http//www.joeinfo.com/gpr/antenna.MOV

18
  • Recently, Dr. Harry Jol, professor of geography
    at the University ofWisconsin - 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
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