Topic 13

Question 1

terrain models and GIS

Answer 1

perhaps the most important type of raste data used in GIS is terrain data often referred to as digital elevation models

Question 2

aquiring terrain data

Answer 2

there are three common ways to collect terrain/elevation data

ground based

airborne direct measurement tech like Lidar

photogrammetric methods

Question 3

ground based surveys

Answer 3

GNSS and total station surveys can ve used to collect elevation data on the ground

Question 4

airborne LiDAR surveys

Answer 4

direct measurement of earths surface features

bare-earth models reveal terrian

Question 5

terrain data from photogrammetry

Answer 5

resurgence of this technoque with advances in digital (softcopy) processing, high-resolution satelittle imaging and drones

Question 6

photogrammetry

Answer 6

science and technology of making measurements from aerial photographs, drone photographs and satelittle imaged

museum artifacts

Question 7

data models
(3)

Answer 7

three common ways to represent terrain

raster digital elevation models (DEM)

triangualted irregular networks (TINS)

elevation contours

spatially quantized (raaster) no smooth and continuous (box steps)

Question 8

dem raster models

Answer 8

most common type of terrain data
sun is walys in the Northwest or Northeast

Question 9

TIN model (vector)

Answer 9

surface model created from vector data using tesselation of triangles that store elevation attributes at the vertices

has advantages over raster

Question 10

constructing DEMS and TINS

Answer 10

Lidar and photogrammetry

ground surveys

Question 11

contouring

Answer 11

usually relate to elevation
create vector representation of breaks

can be done for nearly any feature at interval or ratio scale

isolines
used for visualization

Question 12

isolines

Answer 12

different lines types

contours = isolines for elevation

Question 13

visualizing terrain: contours

Answer 13

important way to visualize terrain data, partiularily for static maps

Question 14

visualizing terrain: hill shading

Answer 14

DEMs and TINs are very useful for geovisualization where terrain interpolation is important

hillshade are also known as shade relief maps

Question 15

hillshading a DEM

Answer 15

automatic shading

can change elevation of the sun

heights and slopes of surfaces used as input

Question 16

unidirectional vs multidirectional

Answer 16

light from one direction or multiple directions

Question 17

class values vs colour ramps

Answer 17

colour ramps = hypsometric tinting

colours end

vs a gradual gradient change

Question 18

Eyton (1990) colour stereoscopic effect

Answer 18

the use of colours and how more complex colour schemes can be harmful to viewer

Question 19

visualizing terrain : vertical profiling

Answer 19

interpret changes in elevation

Question 20

3D rendering of digital surfaces

Answer 20

have become very sophistaced in recent years, and provide a realistic view of terrain surfaces and features

Question 21

slope and aspect measurements

Answer 21

key measurements that can be performed on terrain models

Question 22

slope computations

Answer 22

Raster DEMS

computation is the ratio of two components

vertical component

window distance

convert to % or to degrees

change in elevation over distance (derivative)

Question 23

aspect

Answer 23

direction of slope (derivative)

compass usually from the North

Question 24

surface curvature

Answer 24

terrain, changing slope over space

first derivative of slope

Question 25

slope magnitude

Answer 25

if sloping away from middle (-) if sloping towards centre (+) signs are dependent on which values are subtracted from what

Question 26

relative distance

Answer 26

relative radiance raster

Question 27

precision of slope and aspect maps

Answer 27

sensitive to the quality of information in the elevation model noise in the data different spatial resolutions can result in very small shifts actual locational shift (not perceptual)

Question 28

slope curvature

Answer 28

input map two different import types profile (1 direction) platform (2 direction)

Question 29

deriving slope curvature: profile

Answer 29

straight down = 0 skateboard ramp = + outward curve = -

Question 30

deriving slope curvature: planform

Answer 30

flows outwards from centre = + flows inward from outside = - straight = 0