Digital Elevation Model

Transcription

1 Digital Elevation Model

2 DEM, DSM, DTM? DSM: digital surface model. Height of the earth s surface, including houses, trees, boulders...etc. DTM: digital terrain model. Bare-earth earth surface model. Filtered results of DSM. DEM: digital elevation model. Some people use DEM as DSM, some regard it as DTM. Lately, it is more synonymous to a general terms describing the height of surface.

3 Grid, triangulation, contour-based network Figure 1.2. Methods of structuring an elevation data network: (a) square-grid network showing a moving 3 by 3 submatrix centered on node 5; (b) triangulated irregular network; and (c) contour-based network. Reprinted with permission from Moore, Grayson, and Ladson (1991) Digital terrain modeling: A review of hydrological, geomorphological, and ecological applications. Hydrological Processes 5: Copyright 1991 by John Wiley and Sons Ltd.

4 File format Endian BSQ, BIL, and BIP

5 Image Dimensions Abbreviation Alternative Name M-N-3 BSQ Band-Sequential or Band- Interleaved 3-M-N M-3-N BIP BIL Band- Interleaved-by- Pixel or Pixel- Interleaved Band- Interleaved-by- Line or Row- Interleaved

6 Usage of DEM need to orthorectify your satellite or aerial imagery require 3D visualisation need to extraction information that has a height element observe parameters of landform: roughness, slope Model flow directions Input for numerical models

7 Sources of DEM GTOPO30 < elevation/gtopo30/gtopo30.html> ETOPO2 / ETOPO5 < datasets/etopo2_topography.html> SRTM <ftp://e0srp01u.ecs.nasa.gov> SRTM plus < WWW_html/srtm30_plus.html> Taiwan DEM <

8 Attribute Definition Significance Altitute Elevation Climate, vegetation, potential energy Upslope height Mean height of upslope area Potential energy Aspect Slope azimuth Solar insolation, evapotranspiration, flora and fauna distribution and abundance Slope Gradient Overland and subsurface flow velocity and runoff rate, precipitation, vegetation, geomorphology, soil water content, land capability class Upslope slope Mean slope of upslope area Runof velocity Dispersal slope Mean slope of dispersal area Rate of soil drainage Catchment slope Average slope over the catchment Time of concentration Upslope area Catchment area above a short length of contour Runoff volume, steady-state runoff rate Dispersal area Area downslope from a short length of contour Soil drainage rate Catchment area Area draining to catchment outlet Runoff volumn Specific catchment area Upslope area per unit width of contour Runoff volume, steady-state runoff rate, soil characteristics, soil-water content, geomorphology Flow path length Erosion rates, sediment yield, time of concentration Maximum distance of water flow to a point in the catchment Upslope length Mean length of flow paths to a point in the catchment Flow acceleration, erosion rates Dispersal length Distance from a point in the catchment to the outlet Impedance of soil drainage Catchment length Distance from highest point to outlet Overland flow attenuation Profile curvature Slope profile curvature Flow acceleration, erosion/deposition rate, geomorphology Plan curvature Contour curvature Converging/diverging flow, soil-water contnet, soil characteristics Tangential curvature Plan curvature multiplied by slope Provides alternative measre of local flow convergence and divergence Elevation percentile Proportion of cells in a user-defined circle lower than the center cell Relative landscape position, flora and fauna distribution and abundance

9 Production Traditional survey Modern survey - GPS survey, Leveling...etc. Digitizing contour map LiDAR InSAR

10 S020 I CHSN P049I063 I S029I045 I055 S019 S411 CKLS S412I064 S101 TAPN 991 T986 S035 I001 KLUN I043 S413 KUYN 980 S121 S S020 I CHSN P049I063 I S029I045 I055 S019 S411 CKLS S412I064 S101 TAPN 991 T986 S035 I001 KLUN I043 S413 KUYN S121 S TFLS 971 I TFLS 971 S052 SNHS SNHS S S053 S053 TECS TECS S031 S031 S030 S030 S016 S WNTS A S I449 HTZS 131 JFES CPUL 6389 WNTS A I JFES CPUL I007 S038 S006 I007 s s077 S008 S004 S070 S014 S007 S003 S025 S013 S026 S066 S S012 I004 S067 S064 I045 S052 S105 s072 S045 S024 S071 S S038 s061 S048s074 S053 TECS S031 S030 S007 S003 S044 S070 S014 S025 S026 S066 S s057 I004 S067 S064 s063 S105 s072 S045 I045 S044 S23R JFES CPUL MERK S004 HTZS 5936 I449 S I215 S049 s075 I007 S009 S006 S103 STCS S015 S071 S070 S008 S014 S005 S038 s061 s074 S048 s s077 S047 s059 I047 S s S026 S039 S025 s073 S080 S079 S078 S046 S sant S s S012 s056 S040 I004 S067 s057 S105 S064 s072 S024 S045 s s I S s057 s s I A247 s058 S s073 S080 S079 S078 S046 S sant s s056 S040 S s059 S047 I S012 s s S23R S027 S013 S011 S016 WNTS S015 S069 s058 SNHS S032 s s077 S103 STCS S008 S s073 S080 S079 S078 S046 S sant s s056 S I042 S006 s059 S047 I S069 S011 S005 S015 S TFLS MERK s061 S048s I I301 S017 S009 S103 STCS S s075 S009 S020 I I063 CHSN P049 I045 I168 S029 S411 S I064 I055 CKLS S412 S101 TAPN T S035 KLUN I043I001S413 S S121 I215 S049 I215 S049 MERK KUYN S050 HTZS s075 S I301 S017 S052 S I I S S002 S003 S007 S013 S011 S066 I045 s063 S044 S23R s063 N S010 S043 S010 S010 LIUC S043 S043 S022 S042 N LIUC S022 S042 s002 S021 S041 50mm/yr N LIUC S022 S042 s002 S021 S041 50mm/yr s002 S021 S041 50mm/yr 50 km

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