ALS Data Filtration with Fuzzy Logic

DTM extraction from the ALS (Airborne Laser Scanning) point cloud is a complex task which involves many algorithms and numerical procedures. One of the first steps, performed to remove all of the terrain covering, is data filtration. There is a number of filtration methods and algorithms to chose from. In this paper we would like to propose a filtration method based on fuzzy logic. We present basic information regarding fuzzy logic, the design of fuzzy rules and an example of point cloud processing. For comparison, results from the ATIN filtration method are presented.     

The Little Ice Age signature and subsequent warming seen in borehole temperature logs versus solar forcing model

The ‘low’ in the transient temperature versus depth borehole profiles around 120 m seen from deep temperature logs in the Canadian Prairies (southern Alberta–southern Saskatchewan), as well as in some of the European data, has been interpreted to be related to the Little Ice Age (LIA). Data point to the lowest ground surface and subsurface temperatures occurring in the very late eighteenth to nineteenth centuries. Inversion of these logs shows that surface temperature lows were followed by a recent warming period. Further, the synthetic profiles built on the basis of solar forcing history, stretching as far back as the beginning of the seventeenth century, suggest that the LIA signatures interpreted from the inversion of the borehole temperature logs would be difficult to be explained by known published models of past solar irradiation despite large range of assumed sensitivities for the couplings assumed, and that further forcing needs to be considered.     

Assessment of the Accuracy of SRTM C- and X-Band High Mountain Elevation Data: a Case Study of the Polish Tatra Mountains

Global digital elevation models (DEMs) are an invaluable source of information in large area studies. Of particular interest are shuttle radar topography mission (SRTM) data that are freely available for the scientific community worldwide. Prior to any application, global datasets should be evaluated using reference data of higher accuracy. Therefore, the main objective of this study was to assess the accuracy of the SRTM C-band (version 4) DEM and SRTM X-band DEM of mountainous areas located in Poland and to examine the quality of data in relation to topographic parameters, radar beam geometry, initial voids in data and the presence of forest cover. A DEM from the Central National Geodetic and Cartographic Inventory, Poland, served as a reference. The study consisted of three steps: (i) the computation of vertical errors of the SRTM C- and X-band DEMs, (ii) the examination of any systematic bias in the data, and (iii) the analysis of the relationships between the elevation errors and terrain slope, aspect, local incidence angle, occurrence of voids and land cover. We found that the SRTM C- and X-band DEMs have mean errors equal to 4.31 ± 14.09 and 9.03 ± 37.40 m and root mean square errors equal to 14.74 and 38.47 m, respectively. Only 82 % of the C-band DEM and 74 % of the X-band DEM vertical errors had absolute values below 16 m. We found that the most important factors determining the occurrence of high errors were the distribution of initial voids and high slope angles for the C-band DEM, and local incidence angle, slope, aspect and radar beam geometry for the X-band DEM. In both cases, the presence of forest cover increased the mean error by approximately 10 m.     

Palaeo- and rock-magnetic investigations across Jurassic-Cretaceous boundary at St Bertrand’s Spring,Drôme,France: applications to magnetostratigraphy

Palaeo- and rock-magnetic investigations of the St Bertrand’s Spring (Le Ravin de Font de St Bertrand) locality in France were carried out in order to contribute to, and improve, the stratigraphy of the Jurassic-Cretaceous boundary interval. Magnetic susceptibility shows slightly diamagnetic behaviour in the lowermost part of the profile and an increase (paramagnetic) towards its middle and upper parts. Rock-magnetic measurements throughout the section show magnetite as the main magnetic fraction, together with traces of hematite. Additionally, thermal demagnetization indicates the presence of goethite. Our magnetostratigraphy indicates three normal/reversed polarity sequences; possibly encompassing the magnetozones M19r to the M17n. This suggests that the St Bertrand section straddles the Tithonian/Berriasian boundary and reaches the middle Berriasian sensu lato.     

Local Weighted Linear Combination

The article focuses on one of the most often used GIS‐based multicriteria analysis methods: the weighted linear combination (WLC). The WLC model has traditionally been used as a global approach based on the implicit assumption that its parameters do not vary as a function of geographical space. This assumption is often unrealistic in real‐world situations. The article proposes a new approach to GIS‐based multicriteria analysis. It develops a local form of the global WLC model. The range sensitivity principle is used as a central concept for developing the local WLC model. The principle postulates that the greater the range of criterion values is, the greater the weight assigned to that criterion should be. Consequently, the local criterion weight can be defined for each neighborhood within a study area as a function of the range of criterion values in a given neighborhood. The range of criterion values provides also the base for defining the local value function. The article presents the theory behind the local WLC modeling and illustrates an implementation of the model in a GIS environment.     

Endangering of the Upper Jurassic karst-fissured aquifer in the Krakow Upland (southern Poland)

 A karst-fissured aquifer in the Upper Jurassic carbonate rocks of the Krakow Upland shows a very high yield (safe yield 117 000 m³/day) and belongs to the major groundwater basins (MGBs) of Poland. The uncovered character of the aquifer and its hydraulic structure favor the intensive infiltration and migration of anthropogenic pollutants from the surface. This pollution is caused by agriculture and industry in the proximity of Krakow and the Upper Silesian agglomeration. Progressive degradation of groundwater quality on a regional scale results. Evaluation of the endangering of the aquifer studied is based on the analysis of the time interval of vertical water percolation from the surface, the time interval of groundwater horizontal flow through the aquifer and the duration of water residence in the aquifer derived from tritium data. Quaternary and Cretaceous overburden occur in the Krakow Upland in addition to numerous outcrops of limestones. The time interval of vertical water percolation in highly permeable limestones does not exceed 3 years and in the areas covered by overburden it is from several to 50 years. The mean effective time interval of horizontal groundwater flow through the Upper Jurassic rocks along the flow paths ranges from several months in the areas of direct drainage to over 15 years in the elevated areas of local groundwater divides. The age of water in the rock matrix was determined using tritium data interpreted according to an exponential model and it ranges from 70 years to over 130 years. In karst-fissured systems with a high retardation index (R_p=21) the effective time of water circulation in local drainage basins does not exceed 7 years. The Krakow-Wieluń Upland is the most extensive and uniform karst region in Poland. It is a belt of Upper Jurassic limestone extending from Krakcow in the southeast to Wieluń in the northwest on the northeast slope of the Silesian Upland. Residual hills of Paleogene age separated by infilled karst depressions are the most characteristic features of the Krakow-Wieluń Upland. More than 800 small caves are known in this area, but only two of them reach 1 km of aggregate passage length (Gazek and others 1992). Received: 4 December 1996 · Accepted: 29 April 1997     

Comparison of continuous and discontinuous constitutive models to simulate concrete behaviour under mixed‐mode failure conditions

The paper presents detailed FE simulation results of concrete elements under mixed‐mode failure conditions according to the so‐called shear‐tension test by Nooru‐Mohamed, characterized by curved cracks. A continuous and discontinuous numerical two‐dimensional approach was used. In order to describe the concrete's behaviour within continuum mechanics, two different constitutive models were used. First, an elasto‐plastic model with isotropic hardening and softening was assumed. In a compression regime, a Drucker–Prager criterion with a non‐associated flow rule was used. In turn, in a tensile regime, a Rankine criterion with an associated flow rule was adopted. Second, an isotropic damage constitutive model was applied with a single scalar damage parameter and different definitions of the equivalent strain. Both constitutive laws were enriched by a characteristic length of micro‐structure to capture properly strain localization. As an alternative approach, the extended finite element method was used. Our results were compared with the experimental ones and with results of other FE simulations reported in the literature. Copyright © 2015 John Wiley & Sons, Ltd.