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Copyright 2015 | [email protected] M hnh ha b mt 1
TRNG I HC NNG LM TP. H CH MINH
KHOA MI TRNG & TI NGUYN
B MN GIS & TI NGUYN
KS. Nguyn Duy Lim
in thoi: 0983.613.551
Email: [email protected]
Bi ging: M hnh ha b mt
(Surface modeling)

Copyright 2015 | [email protected] M hnh ha b mt 2
ng dng m hnh b mt a hnh(Applications of Terrain Models)
TRNG I HC NNG LM TP. H CH MINH
KHOA MI TRNG & TI NGUYN
B MN GIS & TI NGUYN
The multi-point visibility analysis result

Copyright 2015 | [email protected] M hnh ha b mt
Ni dung
nh ngha phn tch b mt a hnh (Interpretation of Terrain Model)
Phn loi cc thng s a hnh
Thng s hnh hc (Geometric Terrain Parameters)
Thng s hnh thi (Morphological Terrain Parameters)
Thng s nhn (Visibility Terrain Parameters)
3

Ti liu tham kho
Digital Terrain Modeling- Principles and Methodology
(2005)
Chapter 13
Digital Terrain Modeling- Acquisition, Manipulation and
Applications (2005)
7.3 7.6
Terrain Analysis- Principles and Applications (2000)
Chapter 3, 4
4

Phn tch b mt a hnh
Qu trnh tm hiu cc c im ca b mt a hnhthng qua trch xut/ tnh ton cc thng s.
Thng s hnh hc (Geometric Terrain Parameters)
Din tch b mt (surface area)
Din tch mt chiu (projection area)
Th tch (volume)
Thng s hnh thi (Morphological Terrain Parameters)
dc (slope) Nguy c st l t
Hng dc (aspect) nh sng Mt Tri, Kh nng n gi
Thng s nhn (Visibility Terrain Parameters) Kin trc
im im (point-to-point visibility)
im vng (point-to-area visibility)
5

dc
S thay i cao (rise) theo khong cch (run).
n v thng tnh bng (0l phng, 90 thng ng)
hoc %.
% =
= (
)
6

dc
o lng hng dc nht ca s
thay i cao.
Thng khng song song vi
ct/hng ca DEM, khng i qua
pixel trung tm.
Thay i cao tng i trong cc
pixel ln cn l rt quan trng
Cn tnh ton dc trong vng ln
cn ca pixel
7

dc
Phng php tnh da trn DEM
Kt hp s thay i cao theo phng x v y
= (
) + (
)
8

dc
4 pixel ln cn
9

dc
8 pixel ln cn
10

Hng dc
Hng dc ti mt im l hng dc nht tnh theo gc
phng v (N = 0).
Hng dng chy
Nng lng nh sng mt tri
Vng t phng s khng c hng dc.
11

Hng dc
Phng php tnh da trn DEM
= /
/
Kt qu tnh hng dc trn cho ra l gc hp vi trc
Ox pha ng (gi tr m hoc dng)
Cch chuyn hng dc theo hng la bn (0-360 ):
Nu Aspect 90 th Aspect (mi) = 90 - Aspect
Nu Aspect > 90 th Aspect (mi) = 360 - Aspect + 90
12
+ 90
-90
Ox

Hng dc
4 pixel ln cn
13
Aspect = - atan (-0.15 / 0.45) = 18.4o
Aspect (mi) = 90 18.4 = 71.6o

Hng dc
8 pixel ln cn
14
Aspect = - atan (-0.16 / 0.39) = 22.3o
Aspect (mi) = 90 22.3 = 67.7o

Tm nhn
Tm nhn ca 1 im l tp hp tt c cc im c th
nhn thy t im .
15

Tm nhn
16

Tm nhn
im nhn
ng nhn
17

Tm nhn
nh hng ca vt cn
18

Tm nhn
nh hng ca thay i cao
19

Bi tp v nh
Cho cao ca im nhn A l 5m, cao ca vt cn B
l 15m. Khong cch gia A v B l 10m. Hi c th t
vt C ti v tr xa nht bao nhiu mt so vi A A c th
thy C? Bit rng cao ca C l 30m, B nm gia A v
C.
Gi nguyn v tr ca A, B v C. Bit rng im D c
cao 10m, D nm trn ng thng vung gc ni C vi
mt t. Hi phi t im A cao ti thiu l bao
nhiu mt A c th thy D?
Tnh ton vng nhn theo phng x, din tch tm nhn?
20

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