نتایج : geographic information system سیستم اطلاعات جغرافیایی (930 مورد) مرتب سازی:

  • a gis-based time-dependent seismic source modeling of northern iran

    Keyword(s): earthquakes- / faulting- / frequency estimation- / geographic information systems- / geophysics- / hazards- / seismic response- / geostatistical- / probabilistic seismic hazard analysis- / seismic hazards- / seismic source- / spatial temporals- / tectonic features- / time distribution- / time independents- / seismology- / earthquake-زلزله / magnitude-قدرت / response-پاسخ / hazard-مخاطره / hazard analysis-تجزیه و تحلیل مخاطره / geographic information system-سیستم اطلاعات جغرافیایی
    Author(s): hashemi,m / alesheikh,a.a / zolfaghari,m.r

    the first step in any seismic hazard study is the definition of seismogenic sources and the estimation of magnitude-frequency relationships for each source.there is as yet no standard methodology for source modeling and many researchers have worked on this topic.this study is an effort to define linear and area seismic sources for northern iran.the linear or fault sources are developed based on tectonic features and characteristic earthquakes while the area sources are developed based on spatial distribution of small to moderate earthquakes.time-dependent recurrence relationships are developed for fault sources using renewal approach while time-independent frequency-magnitude relationships are proposed for area sources based on poisson process.gis functionalities are used in this study to introduce and incorporate spatial-temporal and geostatistical indices in delineating area seismic sources.the proposed methodology is used to model seismic sources for an area of about 500 by 400 square kilometers around tehran.previous researches and reports are studied to compile an earthquake/fault catalog that is as complete as possible.all events are transformed to uniform magnitude scale;duplicate events and dependent shocks are removed.completeness and time distribution of the compiled catalog is taken into account.the proposed area and linear seismic sources in conjunction with defined recurrence relationships can be used to develop time-dependent probabilistic seismic hazard analysis of northern iran.© 2017,institute of engineering mechanics,china earthquake administration and springer-verlag berlin heidelberg.

  • statistical analysis of arsenic contamination in drinking water in a city of iran and its modeling using gis

    Keyword(s): arsenic- / geographic information systems- / statistical methods- / water- / water absorption- / arsenic concentration- / arsenic contamination- / atomic absorption spectrophotometer- / concentration distributions- / mean concentrations- / national standard- / variance analysis- / world health organization- / potable water- / atomic absorption spectroscopy- / drinking water- / gis- / modeling- / spectrophotometry- / statistical analysis- / urban area- / water pollution- / ardabil- / iran- / pollution-آلودگی / geographic information system-سیستم اطلاعات جغرافیایی
    Author(s): sadeghi,f / nasseri,s / mosaferi,m / nabizadeh,r / yunesian,m / mesdaghinia,a

    in this research,probable arsenic contamination in drinking water in the city of ardabil was studied in 163 samples during four seasons.in each season,sampling was carried out randomly in the study area.results were analyzed statistically applying spss 19 software,and the data was also modeled by arc gis 10.1 software.the maximum permissible arsenic concentration in drinking water defined by the world health organization and iranian national standard is 10 μg/l.statistical analysis showed 75,88,47,and 69% of samples in autumn,winter,spring,and summer,respectively,had concentrations higher than the national standard.the mean concentrations of arsenic in autumn,winter,spring,and summer were 19.89,15.9,10.87,and 14.6 μg/l,respectively,and the overall average in all samples through the year was 15.32 μg/l.although gis outputs indicated that the concentration distribution profiles changed in four consecutive seasons,variance analysis of the results showed that statistically there is no significant difference in arsenic levels in four seasons.© 2017,springer international publishing switzerland.

  • halophyte species distribution modeling with maxent model in the surrounding rangelands of meighan playa,iran

    Keyword(s): geographic information system-سیستم اطلاعات جغرافیایی
    Author(s): bagheri,h / ghorbani,a / zare chahouki,m.a / jafari,a.a / sefidy,k

    the aim of this study is to examine halophyte species (six species) distribution modeling using the maximum entropy (maxent) method in the surrounding rangelands of meighan playa,central iran.sampling method was random-systematic.a total of 150 plots (30 plots of 2 to 25 m2 in each type) were collected.in each plot,species density and canopy cover were recorded.soil samples were collected at the start and end of each transect from a depth of 0–30 cm and 30–60 cm.soil characteristics,including texture,available water,lime,organic matter,acidity (ph),electrical conductivity (ec) and soluble solute (na+,ca2+,mg2+,k+,co3−2 and hco3−) were measured in the lab.maps of environmental variables,including elevation,slope and aspect were prepared using geographic information system (gis).soil layer maps were prepared using geostatistical method,including semivariogram analysis and kriging interpolation.after preparing maps of environmental variables,plant distribution and modeling was conducted using maxent model.before running the model,the area under the curve (auc),receiver operating characteristics (roc) function,equal sensitivity and specificity method,jackknife test and kappa coefficient were done.models were built for each species using 70% of the data;the remaining 30% was used to test the models.according to the results,species habitats prefer variables such as soil texture,potassium,lime and organic matter.kappa coefficient was considered excellent for species habitats of halocnemum strobilaceum m.bieb.,1819.) (0.91) and aeluropus littoralis (gouan) parl.,1850) (0.89),for salsola incanescens c.a.mey.,1833) (0.84) and halimione verrucifera (m.bieb) aellen,1938) (0.83) as very good,and good for the habitats of suaeda aegyptiaca (hasselq.) zohary,1957) and limonium iranicum (bornm.) lincz.,1952) species (kappa for both=0.7).the results of this study could be used in convenient locations that have resuscitation potential habitat for this species.© 2017,alöki kft.,budapest,hungary.

  • decision support system to find a skid trail network for extracting marked trees

    Keyword(s): artificial intelligence- / forestry- / geographic information systems- / landing- / logging (forestry)- / skidding- / slope stability- / transportation- / analysis techniques- / analytical hierarchy process- / environmental damage- / environmental information- / gis based decision support systems- / routing- / single-tree selection cutting- / timber harvesting- / decision support systems- / planning-برنامه‌ریزی / geographic information system-سیستم اطلاعات جغرافیایی
    Author(s): parsakhoo,a / mostafa,m / shataee,s / lotfalian,m

    careful planning of skid trails as wood extraction routes in forests is an ongoing task and necessary for minimizing the environmental damage.the main objective of this study is to find skid trails to extract marked trees from stand sites to landing sites using a gis-based decision support system (dss) and network analysis techniques,where environmental information is incorporated into the objective.the techniques were applied in a stand where single trees are felled in near-to-nature conditions.this system is called a single tree selection cutting method.parameters considered for mapping the terrain stability include slope,soil and stream network.the analytical hierarchy process was used to estimate the weights of these parameters.routing between marked trees and log landing was done using a gps-tracking survey and then the analysis was done using new route and service area tools in gis.the service area tool shows accessibility of marked trees by skid trails.results showed that on average the length of the route decreased by 6.65 and 19.22% with the use of a new route tool in compartments 29 and 4,respectively.in conclusion,dss techniques increased accessibility of marked trees and decreased the length of the route.

  • landslide susceptibility mapping in bijar city,kurdistan province,iran: a comparative study by logistic regression and ahp models

    Keyword(s): analytic hierarchy process- / geographic information systems- / geology- / hierarchical systems- / land use- / maps- / regression analysis- / sea level- / surveys- / analytical hierarchy process- / bijar- / iran- / kurdistan- / logistic regressions- / roc index- / scai index- / landslides- / landslide-رانش زمین / risk-ریسک / risk-خطرپذیری / geographic information system-سیستم اطلاعات جغرافیایی
    Author(s): abedini,m / ghasemyan,b / rezaei mogaddam,m.h

    landslides and instability slopes are major risks for human activities which often lead to losing economic resources and damaging properties and structures.the main aims of this study are identifying the underlying effective factors of landslide occurrence in bijar,kurdistan province,and evaluating the regions prone to landslide to prepare the susceptibility map using the logistic regression (lr) and analytical hierarchy process (ahp).at first,using field surveys,questionnaires,geological and topographic maps and reviewing the related studies,ten effective factors including the elevation of sea level,slope inclination,slope aspect,geology,distance from the linear elements (fault,road,and river),precipitation and land use were recognized.then,they were processed using arc gis 10 and ilwis 33.the dependent variable included 144 of slopes prone to landslide selected across the region as the landslide data (code 1),and also 144 stable landslide slopes were randomly selected as landslide free data (code 0).the results of the evaluation showed that lr model with pcpt index equals to 83.4;−2ll index equals to 229.226;and roc index equals to 98.5% and landslide susceptibility map based on scai index had high verification in the case study.therefore,75.489% of the area had very low susceptibility,10.037% low susceptibility,3.628% moderate susceptibility,4.062% high susceptibility and 6.784% very high susceptibility.based on the preferences of the ahp method,the weighting of selected parameters was logically performed so that the parameters could be arranged according to their priorities.the results of the ahp model showed that 3.4% of the area had very low susceptibility,30.43% low susceptibility,46.68% moderate susceptibility,18.14% high susceptibility,and 1.33% very high susceptibility.© 2017,springer-verlag berlin heidelberg.