 |
| Titel |
Remote Operated Vehicle geophysical surveys on land (underground), air and submarine archaeology: General peculiarities of processing and interpretation |
| VerfasserIn |
Lev Eppelbaum |
| Konferenz |
EGU General Assembly 2016
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250129885
|
| Publikation (Nr.) |
 EGU/EGU2016-10055.pdf |
|
|
|
|
|
| Zusammenfassung |
| The last Remote Operation Vehicles (ROV) generation – small and maneuvering vehicles
with different geophysical sensors – can fly at levels of a few meters (and even tens of
centimeters) over the earth’s surface, to move on the earth’s surface and in the inaccessible
underground areas and to explore in underwater investigations (e.g., Mindel and Bingham,
2001; Rowlands and Sarris, 2006; Wilson et al., 2006; Rigaud, 2007; Eppelbaum, 2008;
Patterson and Brescia, 2008; Sarris, 2008; Wang et al., 2009; Wu and Tian, 2010; Stall, 2011;
Tezkan et al., 2011; Winn et al., 2012; El-Nahhas, 2013; Hadjimitsis et al., 2013; Hajiyev
and Vural, 2013; Hugenholtz et al., 2013; Petzke et al., 2013; Pourier et al., 2013;
Casana et al., 2014; Silverberg and Bieber, 2014). Such geophysical investigations
should have an extremely low exploitation cost and can observe surface practically
inaccessible archaeological sites (swampy areas, dense vegetation, rugged relief, over the
areas of world recognized religious and cultural artifacts (Eppelbaum, 2010), etc.).
Finally, measurements of geophysical fields at different observation levels could
provide a new unique geological-geophysical information (Eppelbaum and Mishne,
2011).
Let’s consider ROV airborne magnetic measurements as example. The modern
magnetometric equipment enables to carry out magnetic measurements with a frequency of
50 times per second (and more) that taking into account the low ROV flight speed provides a
necessary density of observations. For instance, frequency of observation of 50 times
per second by ROV velocity of 40 km/hour gives density of observation about 0.2
m. It is obvious that the calculated step between observation points is more than
sufficient one. Such observations will allow not only reduce the influence of some small
artificial sources of noise, but also to obtain some additional data necessary for
quantitative analysis (some interpretation methodologies need to have observations at two
levels; upward analytical continuation does not always correspond to available
criteria).
Besides this, the ROV observed magnetic data may be used for obtaining the averaged
values of magnetization of the upper part of geological section along profiles flowing the
inclined terrain relief (it follows from interpretation scheme presented for surface
magnetic investigations in Khesin et al., 1996) and by combination of horizontal and
inclined ROV flights over the flat relief (for air and underwater measurements)
(Eppelbaum, 2010b, 2013b). In many cases the bodies (layers) composing upper part of
archaeogeological section can be approximated by models of thick bed and thin horizontal
plate and intermediate models that make possible application the aforementioned
technologies.
The developed interpretation methodology for magnetic anomalies advanced analysis
(Khesin et al., 1996; Eppelbaum et al., 2000, 2001; 2011a, 2013b, 2015a) may be
successfully applied for any kind of ROV magnetic observations. This methodology includes:
(1) non-conventional procedure for elimination of secondary effect of magnetic temporary
variations, (2) calculation of rugged relief influence by the use of a correlation method, (3)
estimation of medium magnetization, (4) application of various logical-heuristic,
informational and wavelet algorithms for revealing low-amplitude anomalies against the
noise background, (5) advanced procedures for magnetic anomalies quantitative analysis
(they are applicable in conditions of rugged relief, inclined magnetization, and an unknown
level of the total magnetic field for the models of thin bed, thick bed and horizontal circular
cylinder; some of these procedures demand performing measurements at two levels
over the earth’s surface), (6) advanced 3D magnetic-gravity modeling for complex
geological-archaeological media, and (7) development of 3D physical-archaeological model
of the studied area. Integration of magnetic observations with other geophysical
methods may be realized on the basis of multimodel (Eppelbaum and Yakubov, 2004),
informational (Eppelbaum, 2014), or wavelet (Eppelbaum et al., 2011, 2014; Eppelbaum,
2015c) approaches. In Israel, a lot of positive results were derived from magnetic
method employment with application of the abovementioned procedures at numerous
archaeological sites (e.g., Eppelbaum, 2000; Eppelbaum et al., 2000, 2001; Eppelbaum and
Itkis, 2003; 2003a; Eppelbaum et al., 2006, 2010; Eppelbaum, 2010a, 2011a, 2014,
2015a).
Similar effective techniques were developed for the interpretation of microgravity
anomalies (Eppelbaum, 2009b, 2011b, 2015b), temperature anomalies (Eppelbaum,
2009a, 2013a), self-potential anomalies (Eppelbaum et al., 2003b; 2004), induced
polarization anomalies (Khesin et al., 1997; Eppelbaum, 2000), piezoelectric anomalies
(Neishtadt and Eppelbaum, 2012), Very Low Frequency (VLF) anomalies (Eppelbaum,
2000; Eppelbaum and Khesin, 2012). The theoretical analysis indicates that for all
aforementioned geophysical methods a common interpretation methodology may be applied
.
The main peculiarities of the developed non-conventional system for analysis of potential
and quasi-potential geophysical fields are presented in Table 1.
Table 1. Elements of the developed system of geophysical fields processing and
interpretation under complicated environments (on the basis of Khesin et al., 1996,
Eppelbaum and Khesin, 2001; Eppelbaum et al., 2000, 2001, 2004; Eppelbaum and
Yakubov, 2004; Eppelbaum et al., 2006; Eppelbaum, 2009a, 2009b; Eppelbaum, 2010a,
2010b; Eppelbaum et al., 2010, 2011; Eppelbaum and Mishne, 2011; Eppelbaum,
2011a, 2011b; Neishtadt and Eppelbaum, 2012; Eppelbaum, 2013a, 2013b, 2014;
Eppelbaum and Kutasov, 2014; Eppelbaum et al., 2014; Eppelbaum, 2015a, 2015b,
2015c)
Time Terrain Informational, Inverse problem solution Integrated
variation correction multimodel and in conditions of: 3-D integrated
FIELD correction using and wavelet ruggedarbitrary approximation modeling
correlation algorithms relief polari- of anomalous of complex
method for combined zation object by archaeological
identification 1 - 3 4 - 5 media
of desired targets modelsmodels
Magnetic + ⊕ ⊕ + ⊕ ⊕ ⊕ ⊕ ⊕ + ⊕
Gravity + ⊕ + ⊕ ⊕ ⊕ + ⊕ − ⊕
Thermal + ⊕ ⊕ + ⊕ ⊕ ⊕ ⊕ − ◇
Thermal
(ancient climate + ⊕ ⊕ + ⊕ + ⊕ ∗ ∗ ∗ −
analysis)
SP + + + ⊕ ⊕ ⊕ ⊕ − −
VLF + ⊕ ⊕ + ⊕ ⊕ ⊕ ⊕ − −
IP ∗ ⊕ + ⊕ ⊕ ⊕ ⊕ − −
Piezoelectric ∗ ⊕ + ⊕ ⊕ ⊕ ⊕ − −
Note. Symbols "+" and "−" designate availability and unavailability of procedures,
respectively. "⊕" – authors’ modification, "◇" – under preparing. Symbol "∗" designates the
absence of necessity for calculation
The effect of different heights of observation points and the techniques of its correction
was first discussed in magnetic prospecting (Khesin et al., 1996; Eppelbaum et al., 2001).
Taking into account that rugged relief may strongly disturb observed geophysical
anomalies, the corresponding correction for non-flat relief influenced is of high
importance.
In essence, there are only two types of general analytical expressions applicable to the
description of these geophysical fields (Alexeyev et al., 1996; Khesin et al., 1996;
Eppelbaum, 2000). They are
∫ (zs −-z)cosγp +-(xs −-x)sinγp
U1(x,z) = P r2 dxsdzs,
S
(1)
[ ]
∫ (zs − z)2 − (xs − x)2 cosγp + 2(xs − x)(zs − z)sin γp
U2(x,z) = P ------------------------4----------------------dxsdzs,
S r
(2)
where γp = 90o −ϕp,ϕp is the inclination angle of the polarization vector to the horizon, P
is value of this vector (being a scalar in a particular case); S is the cross-section
area of the body; P is the polarization vector (dipole moment of a unit volume);
r = ∘ ------2---------2-
(xs − x) + (zs − z)is the distance from the observation point M(x, z) to a certain
point of the body P(xs,zs)
Therefore, it seems sufficient to illustrate the manipulations taking as examples Eqs. (1)
and (2). The peculiarity of an inclined profile is that the height of the observation point is a
linear function of the horizontal distance, namely
z = xtanω0,
(3)
where ω0 is the inclination angle of the observation.
The transformations are carried out in the following sequence. The inclined coordinate
system x’Oz’ is introduced in such a way that
( ′ ′ )
{ x = x′cosω0 − z′sinω0, }
( z = x sinω0 − z cosω0. )
(4) |
|
|
|
|
|
|