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MHz Antenna (mhz + antenna)
Selected AbstractsContribution of geophysics to outlining the foundation structure of the Islamic Museum, Cairo, EgyptARCHAEOLOGICAL PROSPECTION, Issue 3 2005A. M. Abbas Abstract The Islamic museum was erected in 1896. The building is situated in the heart of Cairo (capital of Egypt) and holds marvellous Islamic antiquities and priceless ancient hand-writing and rare books. Recently, a restoration scheme has been planned to secure the old building which suffers from weakened foundations. In addition, the wooden roofs will be replaced by concrete ones and an extra floor will be integrated into the building. Unfortunately, the architecture construction charts were neither available nor obtainable. Therefore, the structure of the foundations and the base walls of the building had to be outlined. At the time of construction, three major fundamental wall designs were dominant and were to be considered during the work approach. Ground-penetrating radar (GPR) and dipole,dipole resistivity imaging have been integrated to (define the structure of the foundation walls of the building. A Ramac2 system connected to a 500,MHz antenna has been utilized for conducting the GPR survey. In addition, a Terrameter SAS 1000 single channel device has been used for performing the resistivity profiles. At accessible spaces around the building GPR and resistivity profiles were obtained. The GPR analysis has revealed the depth of the foundation walls to be about 0.9,m from the ground surface with a width close to 0.6,m. The wall design is close to a straight wall style. Furthermore, the analysis of the dipole,dipole resistivity measurements has matched the geology of the area, where subsoil anomalies may be due to the scattered limestone blocks that occur in the area. Moreover, the foundation walls have resistivity values that fall into the range of fractured limestone or limestone blocks. A step-wise or inclined foundation wall style has not been indicated through the parallel resistivity profiles. Copyright © 2005 John Wiley & Sons, Ltd. [source] Ground-penetrating radar and geo-electrical simulations of data from the Floridablanca archaeological siteARCHAEOLOGICAL PROSPECTION, Issue 1 2005M. de la Vega Abstract In this work we characterize the electromagnetic response of archaeological remains of a Spanish fortress situated on the Atlantic coast in Patagonia (Argentina). The fortress, part of the Floridablanca colony, founded in the eighteenth century, has been surveyed with non-invasive electromagnetic techniques (ground-penetrating radar (GPR) and the geo-electric method). The surveys indicate the presence of adobe walls of various sizes and width having different preservation states. Use of inversion algorithms alone to interpret the data has not been conclusive in obtaining a reliable model, because many uncertainties remained. To aid the interpretation, we make use of modelling methods to simulate the low- and high-frequency electromagnetic responses of the structures. The walls can be differentiated in spite of the low resistivity contrast with the surrounding media. The resolution of the 500,MHz antenna allows a satisfactory determination of the location of the walls and their conservation state. Similarly, the geo-electrical response has enough sensitivity to detect the inner and major walls. Copyright © 2005 John Wiley & Sons, Ltd. [source] GPR survey to understand the stratigraphy of the Roman Ships archaeological site (Pisa, Italy)ARCHAEOLOGICAL PROSPECTION, Issue 1 2003M. T. Carrozzo Abstract Two surveys with ground-penetrating radar (GPR) were carried out in June and December 2000 at the Roman Ships archaeological site (Pisa, Italy). Both surveys were undertaken at selected locations, placed on the plan of excavation (,5 m from the ground surface), using a GSSI Sir System2 incorporating 35, 100, 200 and 500 MHz centre-frequency antennae. The main purpose of the two surveys was to test the value of radar in respect of penetration depth and, therefore, to reconstruct the geological stratigraphy, given the general not too favourable site conditions. The results showed that most of the GPR data acquired with the 35 MHz antenna were contaminated by strong reflections caused by above-ground objects near the survey lines. In fact, the archaeological area is protected on every side by iron barriers, around 6 m high, in order to guarantee the stability of the walls and to contain the present shallow groundwater. Therefore, it is very important to recognize the reflections through air (surface scattering) and not to confuse them with the reflections from underground geological features. For this purpose higher frequency antennae, less prone to surface scattering problems, although allowing shallower penetration depths, also have been used. Their higher resolution permitted the identification of some anomalies probably related to shallow stratigraphical boundaries, as well as other anomalies probably attributable to archaeological features. Moreover, the numerous measurements carried out in the second survey to estimate the velocity of propagation of the electromagnetic waves in the ground, contributed to a better interpretation of the geology of the site. Copyright © 2003 John Wiley & Sons, Ltd. [source] Investigations regarding Alpine talus slopes using ground-penetrating radar (GPR) in the Bavarian Alps, GermanyEARTH SURFACE PROCESSES AND LANDFORMS, Issue 10 2001Oliver Sass Abstract The applicability of ground-penetrating radar (GPR) for the investigation of loose debris was tested at two sites (Viererkar and Zugspitzplatt). A pulseEKKO 100 GPR system equipped with 25 MHz antennae was utilized. The aim of the investigation was to record the base of the debris layer, and thereby acquire an estimation of the backweathering rates of the adjacent rockwalls. The study areas are situated in the Northern Alps near the German,Austrian border. The sites are characterized by steep limestone rockwalls and extensive talus accumulations. A total of six profiles was surveyed. The method is suitable and effective for a quick survey in this dry, high-ohmic substrate. The GPR system was able to deliver information about the subsurface stratigraphy to c. 70 m depth. The boundary line to the bedrock was discovered , depending upon the profile surveyed ,5 to 25 m below the surface. The base of the debris material sometimes shows no distinct reflection. Buried features (V-shaped furrows, zones overdeepened by ice action, geological structures) could be detected. Arched structures well below the talus,bedrock interface can be interpreted as drainage systems in the karstic bedrock. A thick scree layer of Late Glacial age was separated from a thinner layer on the talus surface, which was related to the Holocene. The backweathering rates were fixed by a calculation of talus volume to c. 100 mm/103 a during the Holocene (Viererkar) and 150,300 mm/103 a (Zugspitzplatt). The detrital formation in north-exposed sites is twice as intense as in south-exposed sites. These results match the rates of recent rockfall in the same area of investigation. The calculated backweathering for the late glacial period is 150,730 mm/103 a. The magnitude of the calculated rockwall retreat lies well within the range of previous measurements. The discrepancy between some weathering rates highlights the fact that recent and past relief formation must be differentiated. Otherwise recent removal rates may be overestimated. Copyright © 2001 John Wiley & Sons, Ltd. [source] Ground penetrating radar survey and stratigraphic interpretation of the Plan du Lac rock glaciers, Vanoise Massif, northern French AlpsPERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2008Sébastien Monnier Abstract Internal boundaries of the Plan du Lac rock glaciers in the northern French Alps were investigated using ground-penetrating radar (GPR) and were correlated with the surface morphology. Data collected using 50,MHz antennae along three profiles were processed in a novel manner by applying modulated automatic gain control to discriminate reflection events according to coherence and continuity patterns. Based on the GPR and morphological analyses, the stratigraphy appears complex, with prominent internal boundaries dividing the features into several depositional units, interpreted as sequential creeping or thrusting events. Copyright © 2008 John Wiley & Sons, Ltd. [source] Ground-penetrating radar investigations into the construction techniques of the Concordia Temple (Agrigento, Sicily, Italy)ARCHAEOLOGICAL PROSPECTION, Issue 1 2007P. M. Barone Abstract Over the past decade, ground-penetrating radar (GPR) has been recognized as being particularly well adapted to the non-destructive survey of archaeological sites. The present work discusses such an application of the GPR to the study of the foundation geometry of the Concordia Temple in Agrigento (Sicily, southern Italy). Radar data were collected using a pulse EKKO 1000 unit (Sensors and Software, Inc.) with 225,MHz antennae. The GPR data show a regular sequence of short reflectors alternating with ,signal blanked' areas located at approximately 50,ns in the peristyle and a continuous horizontal reflector at approximately 30,ns within the inner part of the temple (the cell). These results may indicate that the construction technique used in the temple was not a compact and homogeneous retaining wall, consisting of an outside layer of bricks and various grouting materials, as was previously thought. The two-dimensional images indicate, instead, that the Greeks made use of the geomorphology of the surrounding area, which involved exploiting the surrounding landscape to obtain foundations (artificial and natural) capable of supporting such monumental and stately buildings. Furthermore, the paper demonstrates the validity of this technique to investigate the foundation geometry of an ancient temple, where it is undesirable to apply a destructive technique. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||