Presentation on Digital Elevation Model and related

Digital Elevation Data
DEM : Digital Elevation Mode DSM : Digital Surface Model

DEM data format
 Grid data
 TIN (Triangulated irregular network) data

GRID data
 Raster format
 Interpolated values
 Takes large storage
 Good for network analysis

TIN data
 Vector based representation
 irregularly distributed nodes and lines with three dimensional coordinates (x,y,
and z)
 arranged in a network of nonoverlapping triangles (triangular tessellation)
 Based on Delaunay triangulation
 Density of points α variation in surface heights
 (+) points provide accurate representation of terrain
 (+) fewer points are needed
 (-) less suited for analysis of surface slope, aspect and network analysis

Network analysis using DEM
 Slope , aspect define the path of flow
 Grid vs TIN data

Flow Direction
128 128
2
2 2
2
2
2
4
4
4
8
1 1 2
1
4
2
8
4
4
8
2
1
2
1
1
1
4
1
4
4
4
16
4
8
78
74
72
67
69
56
71
49
58
50
69
64
53
58
44
55
37
22
38
31
48
24
68
74
61
53
47
34
21
12
16
11
19
12
46
49
Elevation
Direction Coding
Flow Direction
128
64
32
16
8 4
1
2

Flow Accumulation
0
0
0
1
0
1
0
2
0
0
0
0
3
0
7
0
5
20
4
0
0
1
0
0
0
2
0
4
1
7
24
35
0
2
2
0
64 128
1
16
8 2
4
32
Direction Coding

Drainage System: deriving streams
1 1
1 2 2
2 2 2 2
2 2
Value = No Data Stream Network
Stream Network
3
1
1
1 1
1
1
1
2 2
2 2
2
Strahler Stream Order

Delineate the contributing area
to a cell or group of cells
(Basin, Catchment,
Contributing area)
Catchment Boundaries
(Drainage Divides)
Pour Points
(Outlets)
Drainage System: deriving watershed

Network analysis: problems in DEM analysis

Hypothetic: How sink looks in Elevation
Model
92 89 88
91 77 80
88 80 79
99 99 98 99 99 98 99 99 98 99 99 98
99 99 98 99 99 98 99 99 98 99 99 98
98 98 97 99 99 98 99 99 98 98 98 97
97 99 95 92 89 88 90 88 80 97 99 95
99 99 98 91 78 78 78 78 89 99 99 98
99 99 98 88 78 77 77 78 78 98 98 97
99 99 97 87 78 77 77 78 76 97 99 95
99 99 95 98 78 78 78 78 90 99 99 98
99 99 98 98 94 91 90 89 93 98 99 99
99 99 98 94 99 98 94 90 90 90 98 98
98 98 97 99 99 98 99 99 89 90 97 99
97 99 95 99 99 98 99 99 89 90 99 99
A cell or set of spatially connected
cells whose flow direction cannot
be assigned one of the eight valid
values in a flow direction raster
SINK

Depression or Sink
 A sink is an area surrounded by higher elevation values, and is also
referred to as a depression or pit. This is an area of internal drainage.
Some of these may be natural, particularly in glacial or Karst topographic
area (Mark, 1988). Also could be mine pits, local depression.

Artifact Removal
Identifying artifact is key
Important to set the extent to remove artifact
Remove only required artifacts at required places
Interpolate values with nearest and lowest

Example of sinks created due to
artifacts

Channel slope: DEM analysis
0 10 kms
1
2
4
8
16
32
64
128
0
871489
2 4 8
1 16
128 64 32
DEM Flow Direction
map
Flow Accumulation
Map
Extracted
Stream network
Isis River
m
1413
238

DEM extracted network vs channel network
0 10 kms
Isis River Isis River Dart Brook

Drainage
network
(Source: DIPNR, NSW)
Drainage network
modified
Extracted Stream network
from burned DEM
Stream
network
+
DEM

Burned
DEM

Stream
network
extraction
0 5 10 kms

Burned DEM extracted network vs channel network
Isis River Dart Brook

Presentation on Digital Elevation Model and related

More Related Content

Similar to Presentation on Digital Elevation Model and related (20)

Recently uploaded (20)

Presentation on Digital Elevation Model and related

Editor's Notes