Geographic Information Systems (GIS)-based spatially distributed model for runoff routing

A method is proposed for routing spatially distributed excess precipitation over a watershed to produce runoff at its outlet. The land surface is represented by a (raster) digital elevation model from which the stream network is derived. A routing response function is defined for each digital elevation model cell so that water movement from cell to cell can be convolved to give a response function along a flow path and responses from all cells can be summed to give the outlet hydrograph. An example application of analysis of runoff on Waller Creek in Austin, Texas, is presented.Waller Creek Working Grou

Mapping Terrestrial Impact Craters with the TanDEM-X Digital Elevation Model

The TanDEM-X mission generates a global digital elevation model (DEM) with unprecedented properties. We use it for mapping confirmed terrestrial impact craters as listed in the Earth Impact Database. Both for simple and complex craters detailed investigations of the morphology of the particular structure and of the surrounding terrain can be performed

KOMPARASI DATA DIGITAL ELEVATION MODEL (DEM) RESOLUSI MENENGAH DALAM MENGESTIMASI KETINGGIAN LAHAN DI KABUPATEN MANOKWARI PROVINSI PAPUA BARAT

Saat ini telah tersedia data Digital Elevation Model (DEM) dalam berbagai resolusi, yaitu resolusi rendah hingga resolusi tinggi. Pada umumnya data DEM tersebut memiliki akurasi yang baik dalam mengestimasi ketinggian suatu lahan. Penelitian ini bertujuan untuk membandingkan 4 (empat) DEM resolusi menengah dalam mengestimasi ketinggian lahan di Kabupaten Manokwari Provinsi Papua Barat yaitu; Space Shuttle Radar Topography Mission (SRTM), ASTER Global DEM, Jaxa’s Global ALOS 3D World, dan Copernicus Digital Elevation Model. Secara umum penelitian ini terdiri atas 3 (tiga) tahapan utama yaitu inventarisasi data DEM, ekstraksi nilai ketinggian dari data DEM, dan komparasi data DEM. Komparasi data dilakukan secara pixel to pixel pada 400 titik sampel yang dipilih secara acak. Disamping itu dilakukan uji T dan uji korelasi untuk mengetahui tingkat perbedaan dan korelasi data DEM. Hasil penelitian menunjukkan bahwa Copernicus GLO-30 Digital Elevation Model memberikan nilai ketinggian lebih tinggi dibandingkan SRTM, ASTER Global Digital Elevation Model, dan Jaxa’s Global ALOS 3D World. Sedangkan Jaxa’s Global ALOS 3D World memberikan nilai ketinggian lebih rendah dibandingkan SRTM, ASTER Global Digital Elevation Model, dan Copernicus GLO-30 Digital Elevation Model. Berdasarkan uji T, terdapat perbedaan yang signifikan antara SRTM, ASTER Global Digital Elevation Model, Jaxa’s Global ALOS 3D World, dan Copernicus GLO-30 Digital Elevation Model dalam mengestimasi ketinggian lahan di Kabupaten Manokwari Provinsi Papua Barat. Meskipun memiliki perbedaan yang signifikan, namun keempat DEM tersebut memiliki korelasi yang kuat dengan nilai koefisien korelasi rata-rata sebesar 0,96

Modeling physical and chemical climate of the northeastern United States for a geographic information system

A model of physical and chemical climate was developed for New York and New England that can be used in a GIs for integration with ecosystem models. The variables included are monthly average maximum and minimum daily temperatures, precipitation, humidity, and solar radiation, as well as annual atmospheric deposition of sulfur and nitrogen. Equations generated from regional data bases were combined with a digital elevation model of the region to generate digital coverages of each variable

Spectral filtering as a method of visualising and removing striped artefacts in digital elevation data

Spectral filtering was compared with traditional mean spatial filters to assess their ability to identify and remove striped artefacts in digital elevation data. The techniques were applied to two datasets: a 100 m contour derived digital elevation model (DEM) of southern Norway and a 2 m LiDAR DSM of the Lake District, UK. Both datasets contained diagonal data artefacts that were found to propagate into subsequent terrain analysis. Spectral filtering used fast Fourier transformation (FFT) frequency data to identify these data artefacts in both datasets. These were removed from the data by applying a cut filter, prior to the inverse transform. Spectral filtering showed considerable advantages over mean spatial filters, when both the absolute and spatial distribution of elevation changes made were examined. Elevation changes from the spectral filtering were restricted to frequencies removed by the cut filter, were small in magnitude and consequently avoided any global smoothing. Spectral filtering was found to avoid the smoothing of kernel based data editing, and provided a more informative measure of data artefacts present in the FFT frequency domain. Artefacts were found to be heterogeneous through the surfaces, a result of their strong correlations with spatially autocorrelated variables: landcover and landsurface geometry. Spectral filtering performed better on the 100 m DEM, where signal and artefact were clearly distinguishable in the frequency data. Spectrally filtered digital elevation datasets were found to provide a superior and more precise representation of the landsurface and be a more appropriate dataset for any subsequent geomorphological applications

Pembuatan Digital Elevation Model Resolusi 10m dari Peta RBI dan Survei GPS dengan Algoritma ANUDEM

This study proposes the generation of Digital Elevation Model (DEM) with spatial resolution of 10m x 10m by re-interpolation of elevation data. Data input for this study includes: (1) digitized datum coordinate from RBI map, (2) sample points surveyed by GPS, (3) digitized contour data fromSRTM DEM and ASTER GDEM2, and (4) digitized stream-network layer from RBI. All collected data were converted to mass point coordinats. On the top of Topogrid-ArcGIS, all points data were interpolated to produce DEM. After that the produced DEM were compared and evaluated to the SRTM and ASTER DEMvisually. The result shows that produced DEM are more accurate to represent the detailed topography of the study areas

Multiple GPS Measurements for Digital Elevation Model

Accurate representation of field topography is required for implementation of precision conservation management practices. Topographic data for the development of agricultural field digital elevation models (DEM) can be acquired using GPS-equipped farm vehicles during field operations. Repeated measurements of elevation data from multiple field operations may improve DEM accuracy over time. However, repeated topographic measurements would consequently increase the volume of data required to be stored, processed and manipulated unless the amount of data passed on between measurement intervals is reduced. For farmers to utilize topographic information effectively and efficiently, processes must be developed to analyze and manage topographic data collected during field operations and to generate DEMs with minimal user input and intervention. This paper presents an overview of the processes needed for utilizing multiple sets of topographic measurements acquired during field operations for the development of agriculture field DEMs. The procedures needed for DEM development include data preparation and cleaning, data reduction and geostatistical analysis with interpolation. Preliminary data analysis is conducted to extract useful information from GPS raw data set for preparation and cleaning prior to data combination process. The data combination and estimation technique presented is used to estimate elevation data without requiring new sets of measurements to be stored and reprocessed every time they are acquired. Finally, the elevation values at unmeasured locations can be predicted using geostatistical analysis and kriging interpolation method is used to predict the DEM surface

Statistical representation of mountain shading

International audienceShadows cast by the mountains themselves have a strong influence on the surface energy balance of mountainous regions. If the influence of shadows is to be included on sub-grid scales in a surface energy balance model, a statistical representation has to be used. Slope components calculated from digital elevation models of areas in North Wales and the French Alps are found to have double-exponential distributions. From this result, expressions are developed for the fractions of the areas that will be either self-shaded or shaded by remote topography as functions of solar elevation and time of day. These expressions are in good agreement with results from a terrain shading model. Keywords: solar radiation, topography, surface energy balance, statistical parameterisatio

Mars digital terrain model

The Mars Digital Terrain Model (DTM) is the result of a new project to: (1) digitize the series of 1:2,000,000-scale topographic maps of Mars, which are being derived photogrammetically under a separate project, and (2) reformat the digital contour information into rasters of elevation that can be readily registered with the Digital Image Model (DIM) of Mars. Derivation of DTM's involves interpolation of elevation values into 1/64-degree resolution and transformation of them to a sinusoidal equal-area projection. Digital data are produced in blocks corresponding with the coordinates of the original 1:2,000,000-scale maps, i.e., the dimensions of each block in the equatorial belt are 22.5 deg of longitude and 15 deg of latitude. This DTM is not only compatible with the DIM, but it can also be registered with other data such as geologic units or gravity. It will be the most comprehensive record of topographic information yet compiled for the Martian surface. Once the DTM's are established, any enhancement of Mars topographic information made with updated data, such as data from the planned Mars Observer Mission, will be by mathematical transformation of the DTM's, eliminating the need for recompilation