1. DIGITAL ELEVATION MODEL (DEM), ITS DERIVATIVES & APPLICATIONS
Summer training project
Carried out at
Regional Remote Sensing Centre-West
NRSC/ISRO, Jodhpur
(1st June – 3rd July, 2015)
Submiitted BY Submitted to-
Shadaab Er. Sagar s. salunkhe
(B. Tech – aerospace Eng ( Scientist/engineer ‘sd’,
With sp. In avionics rrsc – w, nrsc/isro,
Upes, Dehradun) jodhpur)

2. Contents What is a DEM? How are DEMs generated?
What are the types of DEM
Available?
1/7/2015
What are the various
derivatives of DEM?
What can DEMs be used for?

3. What is a DEM?
Digital Elevation Model (DEM) is the digital representation of the land surface elevation with respect to any reference datum
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4. How is a DEM generated? A) From airborne or satellite remote sensing:
RADAR Interferometry with 2 receivers, 60m apart
A) From airborne or satellite remote sensing:
Stereo images, RADAR or LIDAR data are used in a semi-automated process to create a DEM.
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Airborne Laser-scanning or LIDAR

5. How is a DEM generated?
B) From terrestrial measurements with precise land survey instruments. These spot measurements are then interpolated into an elevation surface. With this method, it is costly and time-consuming to cover bigger areas.
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6. Digital hill-shade models generated from a Lidar scan.
DEM, DTM and DSM...
A digital terrain model is a topographic model of the bare earth –terrain relief - that can be manipulated by computer programs.
Digital Surface Model measures the height values of the first surface on the ground. This includes terrain features, buildings, vegetation and power lines etc. DSM's therefore provide a topographic model of the earth's surface.
Digital Surface Model
Digital Terrain Model
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Digital hill-shade models generated from a Lidar scan.

7. Types of Digital Elevation Models…
(a) Gridded DEM (b) TIN DEM (c) Contour-based DEM
Gridded Digital Elevation Model (GDEM) consists of regularly placed, uniform grids with the elevation information of each grid
TIN is a robust way of storing the spatially varying information. It uses irregular sampling points connected through non-overlapping triangles. The vertices of the triangles match with the surface elevation of the sampling point and the triangles (facets) represent the planes connecting the points.
Contours represent points having equal heights/ elevations with respect to a particular datum such as Mean Sea Level (MSL). In the contour-based structure, the contour lines are traced from the topographic maps and are stored with their location (x, y) and elevation information.
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8. What are the various derivatives of DEM?
Aspect
Aspect identifies the downslope direction of the maximum rate of change in value from each cell to its neighbors. It can be thought of as the slope direction.
Slope
For each cell, the Slope tool calculates the maximum rate of change in value from that cell to its neighbors
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9. Phnom Penh Mapping Meetup Feb. 2013
Contour
Contours are lines that connect locations of equal value in a raster dataset that represents continuous phenomena such as elevation, temperature, precipitation, pollution, or atmospheric pressure.
Cut-fill
A cut-and-fill operation is a procedure in which the elevation of a landform surface is modified by the removal or addition of surface material
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Bernd Eversmann, GIZ-CIM

10. Using View-shed and Observer Points for visibility analysis
A view-shed identifies the cells in an input raster that can be seen from one or more observation locations. Each cell in the output raster receives a value that indicates how many observer points can be seen from each location
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11. Scientific applications
What are DEMs used for?
Scientific applications
topographic mapping
A DEM is needed for ortho-rectification of an image, the process of removing the effects of sensor tilt and relief to obtain a photographic map with uniform scale.
Ortho-photo production
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12. What are DEMs used for? Operational Applications Flood modeling
Development of data layers
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13. Military applications
What are DEMs used for?
Military applications
Visibility analysis
Surface navigation
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14. Phnom Penh Mapping Meetup Feb. 2013
Commercial applications
3D representations
Tele - communication
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Bernd Eversmann, GIZ-CIM

15. Thank you!
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