Geographic Information Systems Digital Elevation Models (DEM)
Digital Elevation Model (DEM) Data Sources That You Can Get Easily
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Transcript of Digital Elevation Model (DEM) Data Sources That You Can Get Easily
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Digital Elevation Model (DEM)Digital Elevation Model (DEM)Data SourcesData Sources
That You Can Get EasilyThat You Can Get Easily
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Quadrilateral Data Structure
Geodetic latitudeand longitude onWGS 84 ellipsoid(NAD 83)
Grid cell resolutionconstant N-S butprogressively finer E-W resolution fromequator to pole
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ETOPO2 Global DEMfrom National Geophysical Data Center
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Worldwide Land And Worldwide Land And Sea Elevation DataSea Elevation Data
In MetersIn Meters(3.7x3.7km cells at equator)(3.7x3.7km cells at equator)
Technical Specifications(0,0) (10799,0)
(0,5399) (10799,5399)
2-byte signed integer data5400 rows by 10800
columns116,640,000 byte dataset
Row Major Order
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CleanTOPO2
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Global Land One-km Base Elevation (GLOBE) DEM data from NGDC
•30” x 30” grid cells for the earth30” x 30” grid cells for the earth•Metric data for land areas, NoDataMetric data for land areas, NoData value (-500) given to sea areasvalue (-500) given to sea areas
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Spatial Resolution
0.93 x 0.93 km0.93 x 0.93 kmCells at equatorCells at equator
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Globe 30” x 30” grid cell data structure and tiling, format, and dataset size
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USGS GTOPO30 Global Land DEM
•Integer Metric data for land areas, Integer Metric data for land areas, NoData value (-9999) given to NoData value (-9999) given to sea areas.sea areas.•30” x 30” grid cells for the earth.30” x 30” grid cells for the earth.•Single GRID dataset on ESRISingle GRID dataset on ESRI Data & Maps (21,600 rows x Data & Maps (21,600 rows x 43,200 cols. [1.866GB file])43,200 cols. [1.866GB file])
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USGS Version Has 33 Tiles
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Shuttle Radar Topography Mission (SRTM)3 arc-second (90m) data from USGS EROS
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Grid 2
Each grid is divided into1 degree tiles (1200 x 1200)
for land areas
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•Data are First Data are First Reflective ReturnsReflective Returns•Data Completeness Data Completeness ProblemsProblems
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Voids areVoids areFilled in ESRIFilled in ESRI
Maps and DataMaps and Data90m SRTM Dataset90m SRTM Dataset
Data areData areCompressedCompressed
From 34GB toFrom 34GB to4.33GB4.33GB
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Shuttle Radar Topography Mission (SRTM)1 arc-second (30m) data from USGS EROS
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Each grid is divided into1 degree tiles (1200 x 1200)
for land areas
Grid 4
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SRTM Data are also availablefrom The National Map Seamless Server
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National Elevation Dataset (NED)from The National Map Seamless Server
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National Elevation Dataset (NED)Data Structure
•One-second grid cells for all One-second grid cells for all U.S. states except AlaskaU.S. states except Alaska•31m N-S resolution31m N-S resolution•28m to 20m E-W resolution28m to 20m E-W resolution•NAD 83 lat./long. cell centersNAD 83 lat./long. cell centers from 25from 25° to ° to 50°50° N•Full dataset is about 60GBFull dataset is about 60GB
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Two-second Grid For Alaska
•NAD 83 lat./long. cell centersNAD 83 lat./long. cell centers•62m N-S resolution62m N-S resolution•38m to 21m E-W resolution38m to 21m E-W resolution from 52° to 70°from 52° to 70° N
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National Elevation Dataset (NED)Data Format and Tiling Scheme
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National Elevation Dataset (NED)
1/31/3rdrd (10m) and 1/9 (10m) and 1/9thth (3.3m) (3.3m) Arc-second Grids for Arc-second Grids for
Certain Areas from Certain Areas from The The National MapNational Map Seamless Seamless
ServerServer
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You can buy theYou can buy theData for each stateData for each state
In ArcGIS GRIDIn ArcGIS GRIDformatformat
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Light Detection And Ranging(LIDAR) Data
Uses a laser and sensor to transmit and receive pulses
from reflected surfaces
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Post processing of the return data produces ahighly accurate DEM,typically with 1 meter
spatial resolution.
LIDAR DEMsavailable only forsmall local areas
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USGSUSGSNational Land Cover DataNational Land Cover Data
(NLCD) 2001(NLCD) 20011”x1” Grid1”x1” Grid
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From The National Map Seamless Server