digital elevation model resolution effects on terrain attribute calculation and quantitative soil landscape modeling the accuracy of digital elevation models dem and dem derived products depends on several factors including the horizontal resolution and vertical precision at which the elevation data are represented and the source of the elevation data this accuracy becomes increasingly important as we extend the use of dem data for spatial prediction of soil attributes our objective was to compare terrain attributes and quantitative soil landscape models derived from grid based dem represented at different horizontal resolutions 10 and 30 m represented at different vertical precisions 0 1 and 1 m and acquired from different sources decreasing the horizontal resolution of the field survey dem produced lower slope gradients on steeper slopes steeper slope gradients on flatter slopes narrower ranges in curvatures larger specific catchment areas in upper landscape positions and lower specific catchment areas values in lower landscape positions overall certain landscape features were less discernible on the 30 m dem than on the 10 m dem decreased vertical precision produced a large proportion of points with zero slope gradient and zero slope curvature and a large number of steeply sloping and more highly curved areas differences among dem from different sources were more significant with less accurate representation of depressions and drainage pathways with the usgs dem as compared to the field survey dem empirical models developed from different dem included similar predictive terrain attributes and were equally successful in predicting a horizon depth ahd in the validation data set

magnetic remanence and fabric properties of laboratory deposited hematite bearing red sandstone redeposition experiments of disintegrated hematite bearing sandstone have confirmed a tangent relationship between inclinations of the drm and ambient magnetic field pronounced variations of drm intensities with field inclination are attributed to processes acting during the depositional formation of laminated sediments coinciding azimuthal distributions of remanence and maximum susceptibility directions reflect intrinsic properties of flaky hematite grains in which the magnetic moment is parallel to the direction of maximum susceptibility this parallelism probably depends on magnetic domain configurations

evaluation of morphometric parameters of drainage networks derived from topographic maps and dem in point of floods an evaluation of morphometric parameters of two drainage networks derived from different sources was done to determine the influence of sub basins to flooding on the main channel in the havran river basin balikesir turkey drainage networks for the sub basins were derived from both topographic maps scaled 1 25 000 and a 10 m resolution digital elevation model dem using geographic information systems gis blue lines representing fluvial channels on the topographic maps were accepted as a drainage network which does not depict all exterior links in the basin the second drainage network was extracted from the dem using minimum accumulation area threshold to include all exterior links morphometric parameters were applied to the two types of drainage networks at sub basin levels these parameters were used to assess the influence of the sub basins on the main channel with respect to flooding the results show that the drainage network of sub basin 4 where a dam was constructed on its outlet to mitigate potential floods has a lower influence morphometrically to produce probable floods on the main channel than that of sub basins 1 3 and 5 the construction of the dam will help reduce flooding on the main channel from sub basin 4 but it will not prevent potential flooding from sub basin 1 3 and 5 which join the main channel downstream of sub basin 4 therefore flood mitigation efforts should be considered in order to protect the settlement and agricultural lands on the floodplain downstream of the dam in order to increase our understanding of flood hazards and to determine appropriate mitigation solutions drainage morphometry research should be included as an essential component to hydrologic studies

soil erosion topographic factor ls accuracy calculated from different data sources abstract the availability and precision of topographic data determines the reliability of the calculated slope length and slope gradient ls factor which limits the use of the universal soil loss equation usle and its adapted versions in region scale soil erosion risk assessment one of the common complications is the effectiveness of topographic data with different resolutions or the compatibility of topographic data originated from different sources in this study the topographic data from five common sources 5 m digital elevation model dem based on 1 10 000 topographic maps 5 m topo dem of 1 10 000 25 m dem derived from 1 50 000 topographic maps 25 m topo dem of 1 50 000 30 m aster gdem 30 m and 90 m srtm dems were individually applied to calculate the ls factors of five catchments with distinct terrain characteristics our results show that the computation accuracy of the ls factors in the five study catchments decreased with greater grid sizes derived from the five topographic data sources compared to the most precision 5 m topo dem of 1 10 000 the relative computation error of the mean ls factors was less than 10 when calculated from the 25 m topo dem of 1 50 000 and that was less than 25 from the 30 m aster and 30 m srtm dems for scenarios in gently rolling areas the 90 m srtm dem with the relative computation error less than 15 could be recommended when there are noises on the open sources dems surface therefore depending on the requirements of data accuracy different data sources can be applied individually or in combined to obtain the optimal predictions of the ls factors however such recommendations on data sources proposed in this study appeared to be more applicable for regions with complex terrains further studies over a range of terrain features and spatial scales are required to validate the effectiveness of different topographic data sources in calculating the ls factor

multi risk interpretation of natural hazards for settlements of the hatay province in the east mediterranean region turkey using srtm dem many scientists have recently alarmed natural hazards due to global climate change such natural disasters are coastal inundation in response to sea level rise and or river flooding caused by heavy rain falls additionally earthquakes and etc in terms of natural hazards one of the most sensitive and culturally significant areas in turkey is the hatay province in the east mediterranean region the hatay province is located on such a region which is not only vulnerable to coastal inundation and river flooding but also is a tectonically and seismically sensitive area in this study for taking conservation measures against the natural hazards beforehand and decision making on any future land planning a digital terrain model and a 3d fly through model of the hatay province were generated then quantitatively and or qualitatively interpreted by employing the shuttle radar topographic mission digital elevation model besides stream drainage patterns lineaments and structural geological features were extracted for natural hazard risk interpretation of settlements and their relationships among the landscape characteristics were exhibited by combining tectonic information previously confirmed regarding the sea level rise the coastal inundation risk map indicates that the most vulnerable areas are coastlines of iskenderun arsuz payas and samandag respectively by after analyzing the digital terrain of the study region and stream drainage patterns the karasu valley zone where the amik plain settlements of antakya iskenderun arsuz payas and samandag with their flood plains have the most flooding risk in decreasing order respectively when a heavy raining occurs finally analysis of tectonics has revealed that antakya iskenderun hassa kirikhan samandag payas arsuz altinozu kumlu and hacipasa regions have the most sensitivity to earthquake disaster in the study region

combination of srtm3 and repeat aster data for deriving alpine glacier flow velocities in the bhutan himalaya abstract the present study evaluates the fusion of dems from the advanced spaceborne thermal emission and reflection radiometer aster instrument and the shuttle radar topography mission srtm the study area consists of high elevation glaciers draining through the rough topography of the bhutan himalayas it turns out that the aster derived and srtm3 dems have similar accuracy over the study area but the srtm3 dem contains less gross errors however for rough topography large sections of the srtm3 dem contain no data we therefore compile a combined srtm3 aster dem from this final composite master dem we produce repeat aster orthoimages from which we evaluate the dem quality and derive glacier surface velocities through image matching the glacier tongues north of the himalayan main ridge which enter the tibet plateau show maximum surface velocities in the order of 100 200 m year 1 in contrast the ice within the glacier tongues south of the main ridge flows with a few tens of meters per year these findings have a number of implications among others for glacier dynamics glacier response to climate change glacier lake development or glacial erosion the study indicates that space based remote sensing can provide new insights into the magnitude of selected surface processes and feedback mechanisms that govern mountain geodynamics

validation of surface height from shuttle radar topography mission using shuttle laser altimeter spaceborne interferometric sar insar technology used in the shuttle radar topography mission srtm and spaceborne lidar such as shuttle laser altimeter 02 sla 02 are two promising technologies for providing global scale digital elevation models dems each type of these systems has limitations that affect the accuracy or extent of coverage these systems are complementary in developing dem data in this study surface height measured independently by srtm and sla 02 was cross validated sla data was first verified by field observations and examinations of individual lidar waveforms the geolocation accuracy of the sla height data sets was examined by checking the correlation between the sla surface height with srtm height at 90 m resolution while shifting the sla ground track within its specified horizontal errors it was found that the heights from the two instruments were highly correlated along the sla ground track and shifting the positions did not improve the correlation significantly absolute surface heights from srtm and sla referenced to the same horizontal and vertical datum world geodetic system wgs 84 ellipsoid were compared the effects of forest cover and surface slope on the height difference were also examined after removing the forest effect on srtm height the mean height difference with sla 02 was near zero it can be further inferred from the standard deviation of the height differences that the absolute accuracy of srtm height at low vegetation area is better than the srtm mission specifications 16 m the srtm height bias caused by forest cover needs to be further examined using future spaceborne lidar e g glas data

effect of topographic data geometric configuration and modeling approach on flood inundation mapping summary technological aspects of producing delivering and updating of flood hazard maps in the us have has gone through a revolutionary change through federal emergency management agency s map modernization program in addition the use of topographic information derived from light detection and ranging lidar is enabling creation of relatively more accurate flood inundation maps however lidar is not available for the entire united states even for areas where lidar data are available the effect of other factors such as cross section configuration in one dimensional 1d models mesh resolution in two dimensional models 2d representation of river bathymetry and modeling approach is not well studied or documented the objective of this paper is to address some of these issues by comparing newly developed flood inundation maps from lidar data to maps that are developed using different topography geometric description and modeling approach the methodology involves use of six topographic datasets with different horizontal resolutions vertical accuracies and bathymetry details each topographic dataset is used to create a flood inundation map for twelve different cross section configurations using 1d hec ras model and two mesh resolutions using 2d feswms model comparison of resulting maps for two study areas strouds creek in north carolina and brazos river in texas show that the flood inundation area reduces with improved horizontal resolution and vertical accuracy in the topographic data this reduction is further enhanced by incorporating river bathymetry in topography data overall the inundation extent predicted by feswms is smaller compared to prediction from hec ras for the study areas and that the variations in the flood inundation maps arising from different factors are smaller in feswms compared to hec ras

the influence of aspect on the biological weathering of granites observations from the kunlun mountains china abstract bedrock and boulder weathering in the higher elevation permafrost areas of the qinghai tibetan plateau have usually been ascribed to frost action for short periods during two summers an attempt was made to better elucidate weathering processes in this region a combination of visual observation coupled with rudimentary data regarding removable weathered material from the four cardinal aspects of granite boulders at elevations of 4600 5000 m in the kunlun mountains qinghai tibetan plateau showed that there was a distinct aspect influence south west north east on weathering it was also observed that there were aspect constrained variations in chasmoendolithic communities and for lichen distribution to further aid understanding temperature data for the four aspects were collected for several weeks during the summers of 2 years with data recording at 1 min intervals using ultraresponsive 0 05 s high precision 0 1 c ultrasmall 0 15 mm diameter thermocouples humidity data were also collected at the rock face based on these data an attempt is made to evaluate the nature of granite weathering in this region to better understand what the impact of the lichens endolithic communities was and how this varies use is made of xrd and sem analyses on samples from each aspect in addition iron rich patinas were found on a number of the boulders and these too were analyzed in an attempt to see their relationship if any to the biological action

soil erosion assessment tools from point to regional scales the role of geomorphologists in land management research and implementation geomorphological research has played an important role in the development and implementation of soil erosion assessment tools because policy and management approaches include the use of soil erosion assessment tools soil erosion research directly affects the public in terms of providing information on natural hazards and human impacts and also as the basis for regulatory policy on land management for example soil loss calculations and geomorphological expertise are used to support soil conservation planning both through agricultural legislation that defines maximum tolerable soil loss rates and through federal and local legislation that requires soil erosion controls on many construction sites to be useful for decision makers soil erosion models must have simple data requirements must consider spatial and temporal variability in hydrological and soil erosion processes and must be applicable to a variety of regions with minimum calibration the growing use of erosion models and geographic information systems gis in local to regional scale soil and water conservation raises concerns about how models are used this has prompted interest in methods to assess how models function at management scales and with the types of data that are commonly available to users a case study of a gis based soil erosion assessment tool using the process based water erosion prediction project wepp shows that using commonly available data rather than research grade data can have predictably a significant impact on model results if model results are then used in management decisions it is critical to assess whether the scale and direction of variation in results will affect management and policy decisions geomorphologists provide unique perspectives on soil erosion and can continue to affect policy through soil erosion research this research should focus on fundamental processes but equally important is continued development and evaluation of models that are matched to real world data availability geomorphic settings and information needs d 2002 elsevier science b v all rights reserved

digital terrain modelling a review of hydrological geomorphological and biological applications the topography of a catchment has a major impact on the hydrological geomorphological and biological processes active in the landscape the spatial distribution of topographic attributes can often be used as an indirect measure of the spatial variability of these processes and allows them to be mapped using relatively simple techniques many geographic information systems are being developed that store topographic information as the primary data for analysing water resource and biological problems furthermore topography can be used to develop more physically realistic structures for hydrologic and water quality models that directly account for the impact of topography on the hydrology digital elevation models are the primary data used in the analysis of catchment topography we describe elevation data sources digital elevation model structures and the analysis of digital elevation data for hydrological geomorphological and biological applications some hydrologic models that make use of digital representations of topography are also considered

suitability of spaceborne digital elevation models of different scales in topographic analysis an example from kerala india digital elevation model dem deriving conventionally from contour data of topographic maps provides sufficient information regarding the continuously varying topographic surface of the earth though spaceborne dems are increasingly being used in earth environmental applications suitability of various freely available spaceborne dems e g advanced spaceborne thermal emission and reflection aster shuttle radar topography mapping mission srtm global multi resolution terrain elevation data gmted for topographic and geomorphometric analyzes in tropical regions is yet to be ascertained in this paper comparability of these spaceborne dems among themselves and also with the dem topo prepared from digital contour data of topographic maps is assessed results show that various primary and secondary derivatives of aster and srtm dems provide relatively better precision and substantial agreement with the corresponding parameters derived from topo among the spaceborne dems srtm has relatively higher vertical accuracy root mean square error 17 05 m compared to aster 24 09 m and gmted 32 85 m the vertical accuracy of all the spaceborne dems strongly depends on the relief and ruggedness of the terrain as well as the type of vegetation it is proposed that in the absence of other available and acceptable elevation datasets srtm and aster are equally competent for geomorphometric analysis in tropical regions while gmted shows significant loss of terrain information due to coarser spatial resolution

a comparison of srtm and high resolution digital elevation models and their use in catchment geomorphology and hydrology australian examples the recently released shuttle radar topography mission srtm 3 arc second digital elevation data set provides a complete global coverage of the earth s land surface in this paper we examine the srtm data for three catchments in australia over a range of climates geology and resultant geomorphology to test this new data set the srtm data are compared with high resolution digital elevation models we use basic hydrological and geomorphological statistics and descriptors such as the area slope relationship cumulative area distribution and hypsometric curve along with strahler and networking statistics the above measures describe the surface morphology of a catchment therefore integrating catchment geology climate and vegetation the srtm data were also assessed as input into the siberia landscape evolution and soil erosion model as were runoff properties using a wetness index the results demonstrate that the 90 m srtm data provide a poor catchment representation hillslopes appear as a linked set of facets and display little of the complex curvature that is observed in high resolution data while catchment area slope and area elevation hypsometry properties are largely correct catchment area relief and shape as measured by the width function are poorly captured by the srtm data also results in working statistics are also variable the large grid size of the srtm data also results in incorrect drainage network patterns and different runoff properties consequently care must be used for quantitative assessment of catchment hydrology and geomorphology as in all cases srtm derived catchment area is incorrect and smaller digital elevation grid sizes are required for accurate catchment wide assessment while only a limited number of catchments have been examined we believe our findings are applicable to other areas

10be dating of the narsarsuaq moraine in southernmost greenland evidence for a late holocene ice advance exceeding the little ice age maximum in southernmost greenland near narsarsuaq the terminal narsarsuaq moraine was deposited well outside of a historical little ice age lia moraine adjacent to the modern ice margin using 10be surface exposure dating we determine narsarsuaq moraine abandonment at 1 51 0 11 ka a second set of 10be ages from a more ice proximal position shows that ice has been within or at its historical i e lia extent since 1 34 0 15 ka notably narsarsuaq moraine abandonment was coincident with climate amelioration in southern greenland southern greenland warming at 1 5 ka was also concurrent with the end of the roman warm period as climate along the northern north atlantic sector of europe cooled into the dark ages the warming of southern greenland and retreat of ice from the narsarsuaq moraine is consistent with studies suggesting possible anti phase centennial scale climate variability between northwestern europe and southern greenland other southernmost greenland ice margin records do not preclude a pre lia ice margin maximum potentially concurrent with a narsarsuaq advance prior to 1 51 ka but also lack sufficient ice margin control to confirm such a correlation we conclude that there is a clear need to further determine whether a late holocene pre lia maximum was a local phenomenon or a regional southern greenland ice maximum and if this advance and retreat reflects a regional fluctuation in climate

evaluation of aster gdem and srtm and their suitability in hydraulic modelling of a glacial lake outburst flood in southeast tibet the resolution and accuracy of digital elevation models dems can affect the hydraulic simulation results for predicting the effects of glacial lake outburst floods glofs however for the tibetan plateau high quality dem data are often not available leaving researchers with near global freely available dems such as the advanced spaceborne thermal emission and reflection radiometer global digital elevation model aster gdem and the shuttle radar topography mission data srtm for hydraulic modelling this study explores the suitability of these two freely available dems for hydraulic modelling of glofs our study focused on the flood plain of a potentially dangerous glacial lake in southeastern tibet to evaluate the elevation accuracy of aster gdem and srtm and their suitability for hydraulic modelling of glofs the elevation accuracies of aster gdem and srtm were first validated against field global position system gps survey points and then evaluated with reference to the relatively high precision of 1 50 000 scale dem dem5 constructed from aerial photography moreover the dem5 aster gdem and srtm were used as basic topographic data to simulate peak discharge propagation as well as flood inundation extent and depth in the hydrologic engineering center s river analysis system one dimensional hydraulic model results of the three dem predictions were compared to evaluate the suitability of aster gdem and srtm for glof hydraulic modelling comparisons of aster gdem and srtm each with dem5 in the flood plain area show root mean square errors between the former two as 15 4 m and between the latter two as 13 5 m although srtm overestimates and aster gdem underestimates valley floor elevations both dems can be used to extract the elevations of required geometric data i e stream centre lines bank lines and cross sections for flood modelling however small errors still exist in the cross sections that may influence the propagation of peak discharge the flood inundation extent and mean water depths derived from aster gdem predictions are only 2 2 larger and 2 3 m deeper than that of the dem5 predictions whereas the srtm yields a flood zone extent 6 8 larger than the dem5 prediction and a mean water depth 2 4 m shallower than the dem5 prediction the modelling shows that in the absence of high precision dem data aster gdem or srtm dem can be relied on for simulating extreme glofs in southeast tibet copyright 2011 john wiley sons ltd

morphometrical analysis of two tropical mountain river basins of contrasting environmental settings the southern western ghats india the morphometric analysis of river basins represents a simple procedure to describe hydrologic and geomorphic processes operating on a basin scale a morphometric analysis was carried out to evaluate the drainage characteristics of two adjoining mountain river basins of the southern western ghats india muthirapuzha river basin mrb in the western slopes and pambar river basin prb in the eastern slopes the basins forming a part of the proterozoic high grade southern granulite terrain of the peninsular india are carved out of a terrain dominantly made of granite and hornblende biotite gneisses the western ghats forming the basin divide significantly influences the regional climate i e humid climate in mrb while semi arid in prb the survey of india topographic maps 1 50 000 and shuttle radar topographic mission digital elevation data were used as the base for delineation and analysis both river basins are of 6th order and comparable in basin geometry the drainage patterns and linear alignment of the drainage networks suggest the influence of structural elements the rb of either basins failed to highlight the structural controls on drainage organization which might be a result of the elongated basin shape the irregular trends in rb between various stream orders suggest the influence of geology and relief on drainage branching the dd values designate the basins as moderate to well drained with lower infiltration rates the overall increasing trend of rl between successive stream orders suggests a geomorphic maturity of either basins and confirmed by the characteristic i hyp values the re values imply an elongate shape for both mrb and prb and subsequently lower vulnerability to flash floods and hence easier flood management the relatively higher rr of prb is an indicative of comparatively steeply sloping terrain and consequently higher intensity of erosion processes further the derivatives of digital elevation data slope aspect topographic wetness index and stream power index showing significant differences between mrb and prb are useful in soil conservation plans the study highlighted the variation in morphometric parameters with respect to the dissimilarities in topography and climate

spatial structure and landscape associations of srtm error abstract this paper evaluates the spatial structure of shuttle radar topography mission srtm error and its associations with globally available topographic and land cover variables across a wide range of landscapes two continental scale srtm elevation data samples were extracted along with collocated national elevation dataset ned elevations modis composite forest cover percentage and global ecoregion major habitat type codes the larger punctual sample contained nearly 247 000 sites on a regular grid across the conterminous united states while the smaller areal sample consisted of 37 500 45 45 rectangular regions on a regular grid sub pixel positional mismatch was accounted for by finding and using the best local fit between the 1 arc sec horizontal resolution ned product and the 3 arc sec 3 horizontal resolution srtm product slope and aspect were calculated for all samples using the larger point sample we identified associations between srtm error defined as ned srtm 3 differences with these land cover and terrain derivative variables using the areal sample we developed semivariograms of elevation error for tens of thousands of small regions across the united states as well as for sets of these regions with common slope and landcover properties this facilitated a more comprehensive evaluation of the spatial structure of srtm error than has previously been done the punctual sample rmse was 8 6 m conforming to previous estimates of srtm error but many errors in excess of 50 m were identified nearly 90 of these large errors were positive and correlated with high forest cover percentage overall srtm elevations consistently overestimated the surface forest cover and slope were positively correlated with positive bias a strong association of aspect with srtm error was noted with positive error magnitudes peaking for aspects oriented to the northwest and negative error magnitudes peaking for slopes facing southeast error bias standard deviation and semivariograms differed substantially across ecoregion types these variables were incorporated in a regression model to predict srtm error this model explained nearly 60 of the total error variation and has the potential to substantially improve the srtm data product worldwide using globally available datasets

early silurian paleopole for redbeds and volcanics of the king george iv lake area newfoundland redbeds and felsic and mafic volcanics of the king george iv lake area of the dunnage zone in southwestern newfoundland have been studied paleomagnetically after unfolding both hematite and magnetite carry a consistent direction of magnetization d 29 6 i 1 0 k 19 3 95 11 3 corresponding to a near equitorial paleolatitude 0 5 n 6 and yielding a paleopole at 84 6 e 35 9 n dm 11 3 dp 5 6 a positive fold test shows that the remanence was acquired before devonian deformation a positive conglomerate test and a reversal of the magnetization in a continuous redbed sequence demonstrates that the remanence was acquired at the time of formation which has been assigned to the early silurian on the basis of a u pb zircon date of 431 5 ma no other undisputed primary or pre fold remanence has been reported from atlantic canada for the late ordovician silurian period therefore from paleomagnetic data it is not yet possible to estimate the amount of post silurian movement within

evaluation of aster and srtm dem data for lahar modeling a case study on lahars from popocatepetl volcano mexico abstract lahars are among the most serious and far reaching volcanic hazards in regions with potential interactions of lahars with populated areas and human structures the assessment of the related hazards is crucial for undertaking appropriate mitigating actions and reduce the associated risks modeling of lahars has become an important tool in such assessments in particular where the geologic record of past events is insufficient mass flow modeling strongly relies on digital terrain data availability of digital elevation models dems however is often limited and thus an obstacle to lahar modeling remote sensing technology has now opened new perspectives in generating dems in this study we evaluate the feasibility of dems derived from the advanced spaceborne thermal emission and reflection radiometer aster and the shuttle radar topography mission srtm for lahar modeling on popocatepetl volcano mexico two gis based models are used for lahar modeling laharz and a flow routing based debris flow model modified single flow direction model msf both predicting areas potentially affected by lahars results of the lahar modeling show that both the aster and srtm dems are basically suitable for use with laharz and msf flow path prediction is found to be more reliable with srtm data though with a coarser spatial resolution errors of the aster dem affecting the prediction of flow paths due to the sensor geometry are associated with deeply incised gorges with north facing slopes laharz is more sensitive to errors of the aster dem than the msf model lahar modeling with the aster dem results in a more finely spaced predicted inundation area but does not add any significant information in comparison with the srtm dem lahars at popocatepetl are modeled with volumes of 1 10 5 to 8 10 6 m 3 based on ice melt scenarios of the glaciers on top of the volcano and data on recent and historical lahar events as regards recently observed lahars the travel distance of lahars of corresponding volume modeled with laharz falls short by 2 to 4 km an important finding is that the travel distance of potential lahar events modeled with laharz may differ by about 2 km when using srtm or aster data because of varying lateral flow volume distribution as a consequence verification and sensitivity analysis of the dem is fundamental to deriving hazard maps from predicted modeled inundation areas because of the global coverage of this type of remote sensing data the conclusion that both srtm and aster derived dems are feasible for lahar modeling opens a wide field of application in volcanic hazards studies

early silurian paleolatitude for central newfoundland from paleomagnetism of the wigwam formation redbeds and minor volcanic rocks of the early silurian wigwam formation of the botwood group were sampled in the exploits subzone of the dunnage zone of central newfoundland at 18 sedimentary and 3 volcanic sites thermal demagnetization isolated a shallow northward or southward magnetization d 356 0 i 16 8 k 12 9 95 9 2 n 21 site means after correction for the tilt of bedding a positive fold test demonstrates that this remanence predates regional siluro devonian folding a primary age for the remanence is indicated by positive conglomerate tests on volcanic clasts and reversals correlated with sedimentary stratigraphy antiparallel remanence directions at sites of opposite polarity indicate that the primary remanence is not partially overprinted by a secondary component the exploits subzone of the dunnage zone is interpreted to have been at low paleolatitudes 8 5 s 5 during the early silurian we reached a similar conclusion for the notre dame subzone of the dunnage zone in

analysis and characterization of the vertical accuracy of digital elevation models from the shuttle radar topography mission 1 the first near global high resolution digital elevation model dem of the earth has recently been released following the successful shuttle radar topography mission srtm of 2000 this data set will have applications in a wide range of fields and will be especially valuable in the earth sciences prior to widespread dissemination and use it is important to acquire knowledge regarding the accuracy characteristics in this work a comprehensive analysis of the vertical errors present in the data set and the assessment of their effects on different hydrogeomorphic products is performed in particular the work consisted of 1 measuring the vertical accuracy of the data set in two areas with different topographic characteristics 2 characterizing the error structure by comparing elevation residuals with terrain attributes 3 assessing a wavelet based filter for removing speckle and 4 assessing the effects of vertical errors on hydrogeomorphic products and on slope stability modeling the results indicate that in the two sites relief has a strong effect on the vertical accuracy of the srtm dem in the high relief terrain large errors and data voids are frequent and their location is strongly influenced by topography while in the low to medium relief site errors are smaller although the hilly terrain still produces an effect on the sign of the errors speckling generates deviations in the drainage network in one of the investigated areas but the application of a wavelet filter proved to be an effective tool for removing vertical noise although further fine tuning is necessary vertical errors cause differences in automatically extracted hydrogeomorphic products that range between 4 and 1090

effect of drainage area on hypsometry from an analysis of small scale drainage basins in the siwalik hills central nepal hypsometry of drainage basins area elevation analysis has generally been used to infer the stage of geomorphic development and to study the influence of varying forcing factors i e tectonics climate lithology on topography however the scale dependence of hypsometry has generally been neglected in order to assess the scale dependence of hypsometry this study focuses on the sensitivity of hypsometry to different digital elevation model dem resolutions and on the influence of drainage area hypsometry inferred from different dems is shown to be robust against variations of their resolution however hypsometry appears to be dependent on drainage area we propose that this scale dependence may reflect the varying importance of river and hillslope processes with basin area copyright 1999 john wiley sons ltd

automated classification of landform elements using object based image analysis this paper presents an automated classification system of landform elements based on object oriented image analysis first several data layers are produced from digital terrain models dtm elevation profile curvature plan curvature and slope gradient second relatively homogenous objects are delineated at several levels through image segmentation these object primatives are classified as landform elements using a relative classification model built both on the surface shape and on the altitudinal position of objects so far slope aspect was not used in classification the classification has nine classes peaks and toe slopes defined by the altitudinal position or the degree of dominance steep slopes and flat gentle slopes defined by slope gradients shoulders and negative contacts defined by profile curvatures head slopes side slopes and nose slopes defined by plan curvatures classes are defined using flexible fuzzy membership functions results are visually analyzed by draping them over dtms specific fuzzy classification options were used to obtain an assessment of output accuracy two implementations of the methodology are compared using 1 romanian datasets and 2 berchtesgaden national park germany the methodology has proven to be reproducible readily adaptable for diverse landscapes and datasets and useful in respect to providing additional information for geomorphological and landscape studies a major advantage of this new methodology is its transferability given that it uses only relative values and relative positions to neighboring objects the methodology introduced in this paper can be used for almost any application where relationships between topographic features and other components of landscapes are to be assessed

mean curvature watersheds a simple method for segmentation of a digital elevation model into terrain units abstract terrain segmentation is the process of subdividing a continuous terrain surface into discrete terrain units if the resulting units represent meaningful geomorphic objects the approach may facilitate studies of not only landforms and land forming processes but also the interaction among surface form soil vegetation hydrology and topoclimatic regimes commonly used methods for terrain segmentation fail to produce terrain units with a potentially large but cyclic variation in topographic attributes such as uniformly curved areas bounded by topographic break lines although this topographic characterisation is common for a number of landforms this paper describes a new method for terrain segmentation using mean curvature mec watersheds the method produces objects that contain a cycle of mec values thus the topographic variation within each object may be large but due to the cyclic nature of the mec variation a geometric simplicity is ensured in a case study we show how the resulting terrain units correspond well with a number of landforms and surface types observed in the field and conclude that the method can be expected to be of great value for a number of applications within geomorphology and related disciplines

paleomagnetism and magnetic fabrics from the springdale and wigwam redbeds of newfoundland and their implications for the silurian paleolatitude controversy abstract in many mobile belts paleomagnetic directions from clastic sedimentary rocks are typically shallower than directions from associated igneous rocks this discordance raises questions about the reliability of sedimentary rocks and can lead to controversial paleogeographic reconstructions in newfoundland the controversy over silurian paleogeography arises from a difference between results from clastic redbeds with anomalously shallow directions that place newfoundland at the paleoequator in the silurian and coeval epicontinental volcanics with steeper directions that place newfoundland at a more southerly paleolatitude this study tests the possibility that the anomalously shallow redbed directions are the result of internal strain or inclination error related to deposition we specifically compare coarse and fine grained lithologies under the assumption that such remanence altering effects will be different in rocks with differing mechanical competence we show that inclinations correlate with lithologic variations but in a manner opposite to that predicted for the accumulation of internal strain based upon a strict set of demagnetization criteria clearly defined single component characteristic directions are only observed in the finer grained sandstones these well determined directions yield a pre folding and pre rotational dual polarity magnetization that places newfoundland at a paleolatitude of 23 s 9 in the silurian this revised paleolatitude is consistent with the volcanic results and with the paleolatitude predicted for newfoundland from the north american reference path in contrast coarse grained sandstones yield shallower directions that appear to be composites of opposite polarity magnetizations or weakly defined directions with strongly contaminating overprints because the shallow magnetizations in the coarser grained samples may have originated as a depositional remanence we also suspect inclination error related to deposition the degree of inclination error is consistent with values predicted for redbeds from previously published experimental results these observations suggest that grain size considerations are important in assessing the reliability of redbed magnetizations recognition of the relationship between grain size and remanence acquisition allows us to resolve the silurian paleolatitude controversy for newfoundland

rectification methods comparison for the aster gdem v2 data using the icesat gla14 data in the lvliang mountains china aster gdem data have high spatial resolution and wide coverage which are significant in topographic analysis and geographic study icesat gla14 data can improve the vertical accuracy of aster gdem data based on its abundant points with high vertical accuracy it is essential to seek a proper rectification method for aster gdem data in this research taking the lvliang mountains of china as the study area proper rectification method is explored for the latest version of the aster gdem data aster gdem v2 data the icesat gla14 data are regarded as the real data so the difference between the two datasets is the vertical error data the key to rectify the aster gdem v2 data is to seek an appropriate interpolation method to simulate a proper surface for the vertical error data through analysis and comparison four interpolation methods including inverse distance weighted idw method ordinary kriging ok method simple kriging sk method and universal kriging uk method are first chosen from numerous interpolation methods through comparing the vertical error histograms the samples and the characteristics of the four interpolation methods the icesat gla14 data in 2005 are selected as the benchmark to rectify the aster gdem v2 data then the vertical error data are calculated using the difference value between the aster gdem v2 data and the icesat gla14 data under optimal configuration the vertical error the chosen four interpolation methods are used to simulate the surface of the vertical error data finally the rectified results for aster gdem v2 data are achieved by adding the interpolated results to the aster gdem v2 data and the accuracy of the rectified results is appraised using the ground control points on the topographic maps the research results show that 1 accuracy of the rectified results is different by using various interpolation methods the rmse value range for all the rectified results is 19 5 26 7 m 2 among the four methods sk is the best the next are ok and uk methods which have approximately similar performance but the uk method is a little worse on the whole the idw method has the worst performance 3 this research not only provides the optimal parameters for different interpolation methods but also obtains the appropriate rectification method for aster gdem v2 data using icesat gla14 data which is beneficial for broader range of applications using aster gdem v2 data in topographic and geographic research

quantitative analysis of land surface topography land surface topography significantly affects the processes of runoff and erosion a system which determines slope aspect and curvature in both the down slope and across slope directions is developed for an altitude matrix also the upslope drainage area and maximum drainage distance are determined for every point within the altitude matrix a fortran 66 program performs the analysis

influence of topography on some vegetation cover properties abstract we study the influence of nine local non local and combined quantitative topographic characteristics on vegetation cover altitude and density the objects under study are four areas of the rudny altai differentiation of plant properties is shown to depend on relief parameters which control migration and accumulation of water in landscape by gravity these are landsurface curvatures catchment area topographic and stream power indexes in some cases the phytocoenosis characteristics can have higher correlation with non local and combined topographic variables than with local ones this derives from the fact that non local and combined relief attributes take into account a relative location of an area in a landscape so they can better determine topographic prerequisites of substance motion we demonstrate the advisability of the use of digital models and maps of indicated topographic characteristics in plant investigations