2006 Pawn of a Gambler‟s Game: A Geophysical Survey of St

Pawn of a Gambler’s Game:
A Geophysical Survey of St. Ambrose’s Cemetery,
Deadwood, South Dakota
Jeremy W. Pye, Department of Anthropology, University of Arkansas
Old Main 330, Fayetteville, Arkansas 72701.
Prepared for
Kenneth L. Kvamme
Archeo-Imaging Lab,
Department of Anthropology,
University of Arkansas,
Fayetteville, Arkansas.
December, 2006
ABSTRACT
In October of 2006, a geophysical survey was conducted in a 20 x 40 m portion of the St.
Ambrose’s Cemetery in Deadwood, South Dakota. The survey took place in a section of the
cemetery that was not marked with headstones in and effort to ascertain whether burials were
present in this section, and to identify possible graves. Multiple geophysical instruments were
employed during this survey, including a GSSI SIR 2000 ground penetrating radar, a twin probe
array resistivity meter, and a magnetic gradiometer. The GPR survey used a 400 MHz antenna
and survey wheel, with 40 transects of data collected, each separated by 50 cm. The resistivity
data were also collected in 50 cm transect spacing using a double twin probe array in 10 lines.
The GPR data was processed using time slicing methods in as well as manual profile
interrogation.
2
INTRODUCTION
In October of 2006, a geophysical survey was conducted in a 20 x 40 m portion of the St.
Ambrose’s Cemetery in Deadwood, South Dakota by Dr. Kenneth L. Kvamme of the ArcheoImaging Lab and some of his students. The survey took place in a section of the cemetery that
was not marked with headstones in and effort to ascertain whether burials were present in this
section, and to identify possible graves. Multiple geophysical instruments were employed during
this survey, including a Geophysical Survey Systems, Inc. (GSSI), Subsurface Interface Radar
(SIR) 2000 ground penetrating radar, a Geoscan RM15 resistance meter, and a Geonics EM38
electro-magnetic conductivity meter. The primary goal pf this project was to (1) investigate an
unmarked portion of the St. Ambrose’s cemetery in an effort to identify possible graves, and (2)
assist the South Dakota State Archaeology Officer to delineate the extent of the interments in this
section for the purposes of historic preservation and documentation.
PROJECT AREA
The project are consists of a 20 m E/W x 40 m N/S area within the far back section of St.
Ambrose’s cemetery in Deadwood, South Dakota (Figure 1). Deadwood is located in the Black
Hills of South Dakota, with soils that could be categorized as very rocky, deflated silty clay
loam. This cemetery sits on a southerly facing slope, overlooking the city of Deadwood. The
main portion of St. Ambrose’s cemetery lies to the East of the survey area, and contains earth
works and monuments constructed to combat slope and possibly to also increase the initial depth
to bedrock. The slope of the survey area was relatively uniform at around 15-20% from the top
of the hill toward the north to the bottom of the hill where it flattens out onto a terrace used as an
old road or path. No headstones or monuments occur in this section; however, one metal
temporary gravemarker was encountered in the northwestern section. Many large and small
3
stumps and large pinecones plagued the ground surface impeding the progress of some
instruments. Deadwood had received several inches of snow several days prior to the survey,
and since St. Ambrose’s cemetery lies in an area which does not receive much sunlight during
the day, much of the snow remained. As a result, the ground was relatively moist, providing for
excellent conditions for acquiring good quality data. Excess snow was removed from the ground
surface by raking in order for the instruments to make better contact with the ground surface.
DATA COLLECTION
Multiple instruments were employed during this survey, in order to take advantage of the
beneficial characteristics of each, and to increase the likelihood of identifying possible grave
features in this area. The following discussion will briefly discuss the three instruments which were
utilized in this particular study, the GSSI SIR-2000 GPR, the Geonscan RM15 resistance meter, and
the Geonics EM38 electro-magnetic conductivity meter.
Each of these sections explicitly
interrogates datasets collected from each instrument used in the St. Ambrose’s Cemetery survey, as
well as elaborating on the survey methodology, sampling strategy employed, as well as a discussion
of the data processing and resultant interpretations. Long lengths of 1-inch diameter PVC pipes
were used as corner stakes, and the survey grid was oriented to magnetic north. Fiberglass,
geophysical survey tapes were laid out to guide instrument transects. Prior to survey, the area was
investigated using a metal detector to remove any excessive metallic debris that might have
interfered with magnetic instruments.
The survey methodology and instrumentation used in this
survey will be briefly discussed below, followed by a discussion of the interpretations of the
resultant anomalies.
4
Electrical Resistance
Resistance is an active geophysical technique, which injects a current into the ground
between the mobile and remote probes (Carr 1982; Clark 2000:27-63,171-175;
Gaffney and Gater 2003:26-36). The configurations of the probes produce different results (De
Vore 2006:6; Weymouth 1986:324). However, in this survey, the double twin probe array was
used, resulting in the insertion of five probes in the ground each 0.5 meters from one anther. By
definition, the twin probe array has both a current and voltage probe located on the frame of the
machine and inserted into the ground in a remote location 30 times the spacing distance of the
mobile probes. Therefore, in the Deadwood survey, since the twin probe array spacing was set at
0.5 meters, the remote probes were placed 15-17 meters off of the survey area.
Electrical resistance varies from site to site and within sites depending on several
variables. Since the machine is recording the change in the electric current being applied to the
subsurface, the electrical properties of the soil matrix are important to the propagation of the
current flow. Electrical changes observed by the machine are caused by differing resistance of
materials buried in the soil, as well as differences in soil formation processes and soil chemistry.
Another large part of electrical change derives from disturbances of the soil stratigraphy from
natural or cultural intrusions and modifications (Buck 2003; Clark 2000; Kvamme 2005).
One of the tools used in the Deadwood survey was the Geodscan Reserch RM15
resistance meter, set up with a two meter boom in a double twin probe array set up for spread to
cover more ground. Ten transects were collected over the 20 m X 40 m grid at 0.5 meter
insertion rates, collecting two samples per meter. The data were collected in a parallel fashion,
as some preference in the machine does not allow for a zig-zag survey while using multiple
probes.
5
After collection, the data were downloaded into GEOPLOT by Dr. Kvamme. He applied
a high pass filter to the data to remove low frequency, large scale background values, and later
exported this data in to IDRISI for interpretation. Within IDIRISI, a mean differencing filter was
applied to the resistance data to average the resultant values.
There have been several reports and/ or articles written in past years on cemetery resistance
surveys, including Ellwood (1990, 1994), Imai et al. (1987), Jones (2005a & 2005b) and Kvamme
(2002b). The resistivity data acquired by Kvamme in 2000 shows that is it probable that surface
depressions, cuased by the collapse of a coffin, or the compaction of soil correspond to catch basins
for moisture, lowering resistivity. The results of the resistance survey of St. Ambrose’s cemetery are
depicted in a reverse grayscale in Figure 2. In this image, it appears that the medium to high
amplitude values in grey to black are representative of graves. Thus, it may be concluded that the
graves have relatively higher resistance than the surrounding substrate. The soil here is very rocky,
and therefore the map shows larges areas of high resistance due to the good drainage characteristics
formed by the stones. At the southern end of the survey grid, there appears a linear feature that
looked to be a pathway or road. This feature was created by compaction, and therefore, should be
highly resistant during dry conditions. However due to the snow cover and elevated ground
moisture, this feature would hold water longer than the surrounding area, and therefore shows up as
very low resistance.
Electrical Conductivity
The conductivity survey is an active geophysical technique, which induces an
electromagnetic field, and measures the soil’s capacity for conducting the electrical charge (De
Vore 2006:7;Gaffney and Gater 2003:42-44; Kvamme 2001:362-363). A Geonics EM38
electromagnetic conductivity meter was used in this survey. Both magnetic susceptibility and
6
conductivity were collected, but only the conductivity data will be discussed in this study. The
conductivity data were collected in the continuous mode, except where is proved necessary to
stop the collection to move around large trees. The data were collected in parallel transects at a
0.25 meter traverse spacing from North to South on each of the two grids. After collected, the
data were processed in a similar manner to the resistance data above.
In theory, conductivity is the reverse of resistivity. An electromagnetic field induced
through the transmitting coil and the resultant electromagnetic fields are picked up by the
receiving antenna at the opposite end of the machine. De Vore (2006) states, “the interaction of
the generated eddy loops or electromagnetic field with the earthen materials is directly
proportional to terrain conductivity within the influence area of the instrument” (De Vore
2006:7). As with the resistivity, the conductivity meter records changes in the electromagnetic
field caused by buried objects, differences in soil chemistry or geological strata, or disturbances
from natural or cultural modifications to the soil. Bevan (1991) asserts that conductivity may
sometimes be able to detect the soil difference in the grave shaft, due to differences in
compaction and saturation (Bevan 1991:1310). The anomalies created and seen in the
conductivity map (Figure 3) are also shown as medium gray on this palette.
Ground-Penetrating Radar
The ground-penetrating radar (GPR) system used in this study was a Geophysical Survey
Systems, Inc. (GSSI) Subsurface Interface Radar 2000 (or SIR 2000) that employed a 400 MHz
antenna housed in a fiberglass sled. A survey wheel was attached to this assembly to allow for
continuous data collection. Transect spacing was set at 0.5 meters in a north-south direction
resulting in a total collection of 40 transects in the 20 m x 40 m study area. The data were collected
beginning in the northeast corner using a zig-zag traverse strategy.
7
Forty radar traces were
collected per meter in the y-direction, each digitized in 512 samples.
This methodology should results in data of good quality at this site. The “time window” in
the survey was set at 40nS, however, the radar profiles suggest that the bedrock or some other
definable geologic stratum appears at around 20nS TWTT below the surface. Overall, the radar
return from the subsurface at this site is relatively noisy due to the presence of large subsurface
stones and regolith. Also, surface conditions, i.e. the presence of large stones, large stumps, small
holes, and large pinecones could play a role in the quality of the data collected.
Ground-penetrating radar is a nondestructive, active remote sensing technique, that sends
because electromagnetic radiation into the ground as a stimulus to detect the physical properties of
permittivity, permeability, and electrical conductivity (Conyers 2006:64; France 1992:1455;
Gaffney and Gater 2003:25; Strutt 1994:34). GPR data are acquired by transmitting electromagnetic
pulses into the ground by a transmitting antenna, which are then reflected off buried objects,
archaeological or geological features before being picked up by the receiving antenna (Imai
1987:137-8; Kvamme 2002a:3). This produces a continuous profile of data along the traversed
transect.
The quality of GPR data is dependent on the nature of the soils, the clay content, ground
moisture, depth of object buried, surface topography and vegetation (Nobes 1999; Strutt 1994).
The frequency of the antenna used corresponds to resolution and depth of penetration, for
example, a 900 Mhz antenna might produce reflections from one meter in depth, while a 150Mhz
antenna might penetrate dozens of meters (Conyers 2004; Gaffney and Gater 2003; Strutt 1994).
The expected features must contrast electrically with the surrounding soils to be detected. This
interaction, known as the dielectric constant is a measure of the how much energy is necessary
for the electrical charge to polarize within a soil environment (Strutt 1994:82).
8
Kvamme (2002a) states, “detecting graves is one of the most difficult undertakings in
archeo-geophysics. Unlike buried houses, refuse pits, or ditch systems, graves are very small, and
are generally filled with the same material as the surrounding soil, offering low contrast” (Kvamme
2002a:5). However, the behavior associated with the planning and implementation of cemetery
creation is also valuable to cemetery geophysics. Historic Euro-american burials are usually aligned
in an east-west direction laid in ordered rows, and therefore enhances of interpretations of unnatural
patterns in the subsurface anomalies.
However, due to the fact that graves a relatively small features, about 1 x 2 meters when
considering an adult supine burial, the instrument must pass over the feature a number of times to
build up an observable pattern in neighboring transects. In order to accomplish this, cemetery
surveys are typically conducted in a north-south direction using 0.5 m or 0.25 m transect spacing to
maximize possibility are several returns from a grave. Previous researchers have suggested that
GPR offers the highest probability of grave detection, “owing to its sensitivity to multiple
dimensions of the subsurface and high sampling density” according to Kvamme (2002a:7).
Conyers (2005) states that graves should generally be indicated as hyperbolas or truncation
of undisturbed substrate (Figure 4), yet hyperbolic reflection are not the only responses to graves.
Often, the grave itself, nor the contents of the grave are immediately detectable, what is detected is
the disturbance cause from the digging and filling processes.
It may become necessary to
interrogate the individual soil profiles to ascertain whether a grave is present or not. Bevan (1991)
provides a diagram (Figure 5) which discusses five variables to consider when performing such as
analysis: (1) “burial contrast”, which results in the standard hyperbolic reflection; (2) “subsidence
strata”, which is represented by settling or slumping of the grave fill; (3) “fill scattering”; (4) “strata
break”, or soil substrate truncation; and (5) “surficial subsoil”, or superficial soil truncations or
9
disturbances (Bevan 1991:1311).
The GPR data collected from St. Ambrose’s Cemetery was processed using three different
methods for variable perceptions for interpretation. First, a macro program was written in the GIS
program IDRISI-Andes to transpose all reversed profiles, zero-center the data, remove the
background wavelets, and average and re-gain the data within each of the 40 radar profiles. The
selected tine slice area was windowed out of the overall profile and then those windowed sections
were concatenated together to form the plan view of that nanosecond (nS) time window. The time
slice was then resample to 80 X 160 data points (rows and columns)(see Figure 6). The second
processing method employed Dr. Lawrence Conyer’s time slicing program, GPR_Process to create
similar time-slices to those created in IDRISI. Figure 7 shows a composite time slice from 2 to 20
(nS) below the ground surface generated by GPR_Process and Surfer. Figure 8 shows a vertical
series of 4 nS thick slices between 4 and 16 nS. All time slices were processed with 80 data points
in the x-axis and 160 data points in the y-axis to gain greater interpolation resolution. The third
method of interpretation utilized GPR_Viewer as a tool to remove background waves and re-gain
profiles before manual interpretations. Both manual GPR analysis and machine based image
interpretations of anomalies, which may represent possible graves, will be discussed in the
subsequent section.
ANOMALY INTERPRETATIONS—THE SEARCH FOR GRAVES
Data were collected during survey with the resistance meter, electro-magnetic meter, and
ground penetrating radar. Resistance and EM data are interrogated using a reversed 256-grayscale
palette with black indicating high values. GPR data are displayed using a 256-grayscale, with white
being high amplitude values. All plan map grid images were examined looking for anomalies which
appeared in dimensions similar to graves, a roughly 1 X 2 meter rectangle, and which appeared in
10
some linear arrangement of rows and columns, as is common in historic Euro-American cemetery
settings. The final result of interpretations for this combined multi-instrument survey revealed 62
possible graves and one historic pathway/road, which are depicted in Figure 14. All numbered
possible graves are tabulated in Table 1 to show comparisons of presence or absence in all three
data sets as well as the manual GPR profile interrogation.
The resistance grid can be seen in Figure 9 upon which is overlaid outlined areas marking
anomalies depicting favorable qualities for possible graves. Twenty such areas are shown within the
confines of the resistance grids. These anomalies are believed to be possible graves due to the
occurrence of patterned rows and spacing between graves. Most are discrete features created by
clustering of high data values (for a discussion of the nature of resistance in graves see above).
The conductivity grid appears in Figure 10, and fourteen possible graves are shown in this
image. Only four anomalies were shared by both the resistance and conductivity data. This is an
interesting observation, as it is curious why some graves would be highly resistant and some graves
would be highly conductive, and why some would share these properties. It is possible that this
cemetery was used over a long period of time wherein the behaviors and traditions for grave digging
may have changed to include tamping of the graves, which increases soil compaction.
The ground penetrating radar time slice from 6 to 8 nS below the surface is depicted in
Figure 11 with thirteen anomalies indicated. The GPR time slices shown in Figures 6, 7 and 8
illuminate only a few anomalies in this grid. In this instance, the anomalies indicated as possible
graves were chosen because of dimensionally accurate linear areas of high amplitude values, or
areas which are bounded or headed by a large reflectance source. It is possible that these reflected
buried head or footstones.
As noted by Kvamme (2002a) however, it may be more productive to interrogate individual
11
profiles in an attempt to find possible graves which do not maintain characteristics conducive to
appearance on plan view maps. All forty GPR profiles were examined using the five principals for
grave profile appearance outlined by Bevan (1991), and discussed above. Each hyperbolic anomaly
or characteristic soil disturbance indicative of graves was marked in each profile by a white circle
(see Appendix B). These point data were then combined into a blank raster grid to examine the
spatial relationship of the profile points. Figure 12 shows the resultant image as well as the
interpretive possible grave outlines.
Fifty-four such outlines are shown, of which 51 were
maintained in the final numbered map (Figure 14).
CONCLUSIONS
The geophysical survey of St. Ambrose’s Cemetery in Deadwood, South Dakota has
resulted in the identification of 62 possible graves within the survey area at the westernmost extent
of the cemetery. This section showed few superficial signs of presence of graves. One rile pile that
may be a cairn of some kind appeared off the edge of the grid to the west, however, it is unclear
whether this is marking a grave or if it is just a rock pile. One metal temporary grave marker was
found in the northwest section of the survey grid, roughly placed at the west end of possible grave
number 28 (see Figures 1 and 14). This possible grave is the strongest possible hit in this study, as
it was picked up by all methods employed. Even though the surface revealed little evidence, the
subsurface investigation yielded data of good quality and the resultant interpretations reveal a
cemetery laid out in ordered rows with all graves oriented in an E/W direction, or a N, NE/S/SW
direction. If for no other reason, this study has proven the benefit of using multiple instruments onsite and multiple methods of interpretation during data processing.
12
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1991 The Search for Graves. Geophysics 56(9):1310-1319.
Bevan, B. W., and Jeffrey Kenyon
1995 Ground-Penetrating Radar For Historical Archaeology. MASCA (Museum Applied
Science Center for Archaeology) Journal 11(2):2-7.
Buck, S. C.
2003 Searching for Graves Using Geophysical Technology: Field Tests with Ground
Penetrating Radar, Magnetometry, and Electrical Resistivity. Journal of Forensic
Sciences 48(1):5-11.
Carr, Christopher
1982 Handbook on soil Resistivity Surveying: Interpretation of data from Earthen
Archaeological Siites. Center for American Archeology Press, Evanston, Illinois.
Clark, Anthony
2000 Seeing beneath the Soil: Prospecting Methods in Archaeology. Reprint.
Routledge, London. Originally published in 1996 by B. T. Batsford Ltd.,
London.
Conyers, L. B.
2004 Ground-Penetrating Radar for Archaeology. AltaMira Press, a division of
Rowman & Littlefield Publishers, Inc., Walnut Creek, California.
2006 Ground-Penetrating Radar Techniques to Discover and Map Historic Graves.
Historical Archaeology 40(3):64-73.
DeVore, S.
2006 Geophysical Investigations of a Suspected Historic Grave at Yellowstone
National Park, Park County, Montana. Midwest Archaeological Center, National Park
Service, Lincoln, Nebraska. Submitted to Superintendent, Yellowstone National Park,
Wyoming.
Ellwood, B. B.
1990 Electrical Resistivity Surveys in Two Historical Cemeteries in Northeast Texas: A
Method for Delinieating Unidentified Burial Shafts. Historical Archaeology 24(3):91-98.
Ellwood, B. B., Douglas W. Owsley, Suzanne H. Ellwood, and Patricia A. Mercado-Allinger
1994 Search for the Grave of the Hanged Texas Gunfighter, William Preston Longley.
Historical Archaeology 28(3):94-112.
France, D. L., Tom J. Griffin, Jack G. Swanburg, John W. Lindemann, G. Clark Davenport,
Vickey Trammell, Cecilia T. Armbrust, Boris Kondratieff, Al Nelson, Kim Castellano, and Dick
Hopkins
13
1992 A Multidisciplinary Approach to the Detection of Clandestine Graves. Journal of
Forensic Sciences 37(6):1445-1458.
Gaffney, Chris, and John Gater
2003 Revealing the Buried Past: Geophysics for Archaeologists. Tempus Publishing
Ltd., Stroud, Gloucestershire.
Imai, T., Toshihiko Sakayama, and Takashi Kanemori
1987 Use of Ground-Probing Radar and Resistivity Surveys for Archaeological
Investigations. Geophysics 52(2):137-150.
Jones, G.
2005a Imaging the Buried Past. The American Surveyor (July/August):1-4.
2005b Mapping Unmarked Graves at Layman's Cemetery. Hennepin History:In Press.
Kvamme, K. L.
2001 Current Practices in Archaeogeophysics: Magnetic, Resistivity, Conductivity, and
Ground-Penetrating Radar. In Earth Sciences and Archaeology. Paul Goldberg, Vance T.
Holliday, and C. Reid Ferring (eds.), pp. 353-384. Kluwer Academic/Plenium Publishers,
New York.
2002a Geo-Radar Investigations at the Fort Riley Cemetery, Kansas. Department of
Anthropology & Center for Advanced Spatial Technologies. University of Arkansas,
Fayatteville, Arkansas. Prepared for Directorate of Environment and Safety, Fort Riley,
Kansas.
2002b Final Report of Geophysical Investigations at the Fort Clark and Primeau's
Trading Posts, Fort Clark State Historic Site (32ME2): 2000-2001 Investigations.
ArcheoImaging Lab, Department of Anthropology and Center for Advanced Spatial
Technologies, University of Arkansas, Fayetteville, Arkansas. Submitted to
PaleoCultural Research Group.
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AltaMira Press, Lanham, Maryland.
Nobes, D. C.
1999 Geophysical Surveys of Burial Sites: A Case Study of the Oaro Urupa.
Geophysics 64(2):357-367.
Strutt, M.
1994 Rediscovering the Dead: Practical Applications of Remote Sensing in Historic
Cemeteries. In Volumes in Historical Archaeology, edited by S. South. vol. XXV. The
South Carolina Institute of Archaeology and Anthropology. The University of South
Carolina, Columbia, South Carolina.
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Appendix A:
Figures and Table
15
Figure 1: Surface plan map of St. Ambrose’s Cemetery, Deadwood, South Dakota.
16
Figure 2: Resistance grid, 20 x 40 m with a3 x 3 mean and high filter.
17
Figure 3: Conductivity grid, 20 x 40 m with a3 x 3 mean and high filter.
18
Figure 4: Example of regular spacing between hyperbolic anomalies at the Fort
Riley Cemetery, Manhattan, Kansas (Kvamme 2002a).
Figure 5: Examples of possible soil contrasts that might suggest a grave in radar profile.
The dashed lines denote grave shaft, while the hatched areas represent the different soil
contrasts.
19
Figure 6: Ground Penetrating Radar time slice between 6
and 8 nS, in the TWTT window. This image was produced
using modules within IDRISI using 160 data points in the ydirection and 80 data points in the x-direction.
20
Figure 7: Ground Penetrating Radar time slice between 2-20nS,
in the TWTT window. Selected for 160 data points in the xdirection and 80 data points in the y-direction.
21
0-4nS TWTT
N
4-8nS TWTT
8-12nS TWTT
12-16nS TWTT
Figure 8: Vertical Stacking of neighboring time slices between 0 and 16 nS on a
TWTT window.
22
Figure 9: Image map of resistance survey with outlines of possible graves in white.
Figure 10: Image map of conductivity survey with outlines of possible graves in white.
23
Figure 11: Image map of GPR survey, time slice 6-8 nS TWTT with outlines of possible graves.
Figure 12: Image map of conductivity and resistance surveys. Black points denote anomalies in
GPR profiles consistent with possible responses to graves, while white outlines denote projected
graves where three or more profile hits appear in relative linear clustering.
24
Figure 13: Plan view map of projected graves from all geophysical surveys. Orange polygons
represent possible graves shown in the resistance data. Green polygons show possible graves
from conductivity data. Red polygons show possible graves from GPR data. Cyan polygons
represent possible graves from GPR profile interrogation.
Figure 14: Final plan map showing the location and sequential numbering of all anomalies
demarcated as possible graves.
25
Table 1: Table showing anomaly number and presence or
absence in specified dataset, where “X” denotes present.
Anomaly
#
Resistance
Conductivity
GPR
GPR
Profile
(orange)
(green)
(red)
(cyan)
1
X
2
X
3
X
4
X
5
X
6
X
7
X
8
X
9
X
X
10
X
X
11
X
12
X
13
X
14
X
15
X
X
16
X
X
X
X
X
X
X
17
X
18
X
19
X
X
X
20
X
21
X
22
X
23
X
24
X
X
X
25
X
26
X
X
27
X
X
28
X
X
X
29
X
X
30
X
X
31
X
X
32
X
X
X
33
X
X
34
X
X
35
X
26
X
36
X
X
X
37
X
X
X
38
X
X
39
X
X
40
X
41
X
X
X
42
X
X
X
43
X
44
X
45
X
46
X
47
X
48
X
49
X
50
X
51
X
52
X
53
X
54
X
55
X
56
X
57
X
58
X
59
X
60
X
61
X
62
X
X
27
Appendix B:
Manual Interrogation of Radar Profiles
28
0m
40 m
0 nS –
20 nS –
TWTT
40 nS –
File 1
File 2
File 3
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File 4
File 5
File 6
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File 7
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File 9
31
File 10
File 11
File 12
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File 16
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File 19
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35
File 22
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File 25
File 26
File 27
37
File 28
File 29
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File 31
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File 34
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File 40
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