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Ákos Halmai

    Ákos Halmai

    In this paper we present a new method and file format which allows to create, store and manipulate multiresolution raster images. “Classic ” raster images are built up by rasters (pixels) where in the same image each raster (pixel) has... more
    In this paper we present a new method and file format which allows to create, store and manipulate multiresolution raster images. “Classic ” raster images are built up by rasters (pixels) where in the same image each raster (pixel) has the same size. Multiresolution raster image (mri) are unlike the “classic ” raster images. An mri file is a regular text file, conformed xml 1.0 standard and allows: 1) to store raster based images with different resolution in the same file and in the same time (i.e., allows to contain rasters with different size in the same image); 2) to export easily any part of the image as a separate raster image and to import an image as a part of a raster; 3) to define geographical reference for a raster image and use this image as a raster based GIS model; 4) to perform computations (i.e., image manipulation) on the content of the file. It is an important characteristic of the mri format that mathematical operations could be per-formed always in the same resolu...
    Our monograph concerns different rivers and scales and consists of three main chapters. The first presents the theoretical background and arguments for the interdisciplinary study of river channel evolution, floodplain lakes and different... more
    Our monograph concerns different rivers and scales and consists of three main chapters. The first presents the theoretical background and arguments for the interdisciplinary study of river channel evolution, floodplain lakes and different parts of fluvial system; the second describes UAV mapping methodology in detail and the third provides case studies from different sites of the V4 region.
    Constructions of dams influence river courses by cutting off sediment delivery and altering flow regime. We conducted flume experiments to study how sediment starvation, flow deficit and occurrence of series of floods with sediment load... more
    Constructions of dams influence river courses by cutting off sediment delivery and altering flow regime. We conducted flume experiments to study how sediment starvation, flow deficit and occurrence of series of floods with sediment load influence the evolution of channel planform. Results indicated that reduced flow caused a transition from a braided to incised single-thread planform with remains of inactive channels. The planform resembled rivers suffering from flow reduction caused by dams and constructions of irrigation canals (e.g., Central Platte River, USA). Simulation of series of floods with no sediment delivery caused the formation of an anabranching planform with incised main channel, alluvial islands, and side channels active at high flows. This evolution corresponds to river courses altered by sediment starvation and series of floods (e.g., the lower Drava River, Hungary). Floods with delivery of fines created a single-thread, incised channel with terraces along banks. S...
    Floodway delineation, zoning and hydrodynamic modelling for a section of the Drava River was carried out with  MIKE 21 software at a one-time input flood pulse of 3000 m3s-1 discharge. The objective of the current study was the... more
    Floodway delineation, zoning and hydrodynamic modelling for a section of the Drava River was carried out with  MIKE 21 software at a one-time input flood pulse of 3000 m3s-1 discharge. The objective of the current study was the delineation and mapping of floodway zones in the form of a set of georeferenced GIS data for the section between Őrtilos (river kilometer 236 km) and Drávaszabolcs (70.2 km). Zonation was based on water velocities. Four zones were delineated upstream Barcs, and three between Barcs and Drávaszabolcs, where, due to the confined floodplain downstream Barcs, no stagnant water area was identified. Specific velocities ranged between 0.089 and 3.476 m2s-1 and 0.075 and 2.01 m2s-1 upstream and downstream Barcs, respectively, markedly lower than stated in the Government Decree (0.2 to 6.0 m2s-1). The primary and secondary conveyance zones covered a combined area of about 40% of the entire floodplain, while the remaining 60% included both the transitional and stagnant ...
    Sonar survey of shallow water bodies has challenged scientists for a long time. Although these water courses are small, still they have an increasing ecological, touristic and economical role. As maritime sonars are non-ideal tools for... more
    Sonar survey of shallow water bodies has challenged scientists for a long time. Although these water courses are small, still they have an increasing ecological, touristic and economical role. As maritime sonars are non-ideal tools for shallow waters, the bathymetric survey of these rivers has been taken with cross-sectional methods. Due to recent developments, interferometric surveying technology have also burst into the market of recreational-grade fish-finders. The objective of the current study was the development of a novel, complex and integrated surveying technique which is affordable, robust and applicable even at low water levels. A recreational-grade sonar system was assembled and mounted on a double-hull vessel and connected with a geodetic Global Navigation Satellite System (GNSS) device. We have developed a novel software which enables the bridging between a closed sonar file format and the commonly used Geographic Information System (GIS) datasets. As a result, the sev...
    Adaptation to climate change demands the optimal and sustainable water management in agriculture, with an inevitable focus on soil moisture conditions. In the current study we developed an ArcGIS 10.4. platform-based application... more
    Adaptation to climate change demands the optimal and sustainable water management in agriculture, with an inevitable focus on soil moisture conditions. In the current study we developed an ArcGIS 10.4. platform-based application (software) to model spatial and temporal changes in soil moisture in a soy field. Six SENTEK Drill & Drop soil moisture sensors were deployed in an experimental field of 4.3 hectares by the contribution of Elcom Ltd. Soil moisture measurement at each location were taken at six depths (5, 15, 25, 35, 45 and 55 cm) in 60-minute intervals. The model is capable to spatially interpolate monitored soil moisture using the technique. The time sequence change of soil moistures can be tracked by a Time Slider for both the 2D and 3D visualization. Soil moisture temporal changes can be visualized in either daily or hourly time intervals, and can be shown as a motion figure. Horizon average, maximum and minimum values of soil moisture data can be identified with the buil...
    Computer-aided colour analysis can facilitate cyclostratigraphic studies. Here we report on a case study involving the development of a digital colour analysis method for examination of the Boda Claystone Formation which is the most... more
    Computer-aided colour analysis can facilitate cyclostratigraphic studies. Here we report on a case study involving the development of a digital colour analysis method for examination of the Boda Claystone Formation which is the most suitable in Hungary for the disposal of high-level radioactive waste. Rock type colours are reddish brown or brownish red, or any shade between brown and red. The method presented here could be used to differentiate similar colours and to identify gradual transitions between these; the latter are of great importance in a cyclostratigraphic analysis of the succession. Geophysical well-logging has demonstrated the existence of characteristic cyclic units, as detected by colour and natural gamma. Based on our research, colour, natural gamma and lithology correlate well. For core Ib-4, these features reveal the presence of orderly cycles with thicknesses of roughly 0.64 to 13 metres. Once the core has been scanned, this is a time- and cost-effective method.
    We reviewed the evolution history of SE Transdanubia and, based on plate tectonic changes, we chose characteristic time intervals which represent its most important stages. For a lively illustration of the paleogeographical conditions we... more
    We reviewed the evolution history of SE Transdanubia and, based on plate tectonic changes, we chose characteristic time intervals which represent its most important stages. For a lively illustration of the paleogeographical conditions we searched for present-day analogues. The key selection criterion was the type of sedimentation, which usually also implied similar climate, while tectonic position was only a third-rank consideration. Under the Google Earth satellite image and topography of the selected area we depicted in a block diagram the general structure and the formations of SE Transdanubia at the given time. The detailed colour images of the maps, stratigraphical columns and block diagrams are accessible at the following URL: http://foldrajz.ttk.pte.hu/foldtan/dk-dunantul/index.html