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DIGITAL PHOTOGRAMMETRY :-
A REAL TOOL FOR CREATING
DIGITAL TOPOGRAPHICAL DATABASE
M.V.BHAT, O.P.TRIPATHI, P.K.DAS &
B.TRIPATHY
Survey of India, Survey Training Institute,
Uppal , Hyderabad –
500 039
E-mail : surtrain@hd2.dot.net.in
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OBJECTIVE
A case study of topographic data collected by Sample photogrammetric survey
both from Analogue and
Soft copy photogrammetric systems. It also aims at weighing the merits of DPWS over Analogue Instruments.
INTRODUCTION
A topographical map has vast repository of information useful for various planner and persons engaged in
developmental activities. It is only the maker of this maps knows about the Herculean task that is involved for
collection of topographical information for such maps directly from fields. The photogrammetric technology
together with analogue plotter in early 70’s brought a radical change in mapping technology easing the task
of data
collection. Today we pickup any map is a Stereo metric map. In
this age of information technology automation
and computerization are predominant. Everything is being converted into digital form. Often we hear of digital
sound, digital camera , digital photo , digital theodolite and so on. Mapping is no exception to it. Today a map
means a Digital Topographical DataBase
(DTDB). Paper maps are being referred to as Hard copy maps.
To facilitate topographical data collection in digital form Photogrammetrists by their continual effort
brought in Analytical plotters and subsequently the Digital Photogrammetric Work Stations (DPWS) . The DPWS
popularly known as Soft copy Photogrammetry is becoming user friendly and gradually substituting other
analogue and analytical systems. The real strength of this system is that, it has a number of applications of
photogrammetric technology in the same environment.
To facilitate topographical data collection in digital form Photogrammetrists by their continual effort
brought in Analytical plotters and subsequently the Digital Photogrammetric Work Stations (DPWS) . The DPWS
popularly known as Soft copy Photogrammetry is becoming user friendly and gradually substituting other
analogue and analytical systems. The real strength of this system is that, it has a number of applications of
photogrammetric technology in the same environment
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 PHOTOGRAMMETRY
ANALOGUE
SYSTEM
SOFTCOPY
SYSTEM
MCP SELECTION
Inner Orientation
Relative orientation
Model coordinate
observation
Adjustment
C
O
N
T
R
O
L
E
X
T
N.
Inner Orientation
Auto Tie Points
generation
Adjustment
C
O
N
T
R
O
L
E
X
T
N
IO
RO
AO
GRAPHICAL
FEATURE
EXTRACTION
M
A
N
U
A
L
P
L
O
T
T
I
N
G
D
I
G
I
T
A
L
F E A T U R E
E T R A C T I O N
DIGITIZATION
D T D B
STEPS FOR CREATION OF DTDB
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As evident from the table in addition to the least steps involved for feature extraction most of the work are
being automated with development of suitable algorithm.
As a part of case study a block of 9 models falling in sheet No. 56/K/11 was taken. The specification of
photographs are as under.
Specification No.-
NRSA -
100
Date / Year of Photography
Strip No.
21, 22, 23
Photo No’s
21/34-37, 22/37-40,23/34-37
Scale of photography.
1:10000
Focal Length
304.987mm
SYSTEM USED
For analogue method the instruments used is Wild A8
For Soft copy Photogrammetry the system configuration is as under
Pentium III
ERDAS IMAGING PACKAGE
COMPARISION OF CONTROL EXTENTION BY BOTH METHODS
A set of maps were chosen for photogrammetric control extension.
The method of adjustment adopted in
analogue system was IMT using PATM43 Program
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 The method of adjustment in softcopy system was inbuilt bundle adjustment technique. Which in theoretically
treated to be more precise and accurate. The comparison of results obtained from both technology are tabulated as
follows.
characteristics
Analogue softcopy
rms error (Units)
Mx=0.396,My=0.431,Mz=0.229
Mx=0.1414,My=0.7263,Mz=1.4958
no of control
7
7
lowest discrepancies (Units)
X=0.692, Y=0.010,Z=0.031
X=0, Y=0, Z=0
Highest Discrepancies (Units)
X=-0.694, Y=1,087, Z=0.388
X=0,1849, Y=1,1825, Z=-2,2830
remarks
DIGITAL PLOTTING VIS-À-VIS ANALOGUE PLOTTING
In analogue method plotting was carried out in A8 instrument in
normal SOI pattern. Where as in soft
copy photogrammetry system the feature table was used as supplied by the system. Then it was plotted in 1:10,000
scale.
Both the plots were superimposed and found to be matching very nicely. The plots are attached h/w for
reference.
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TIME COMPARISION
CHARACTERSTICS
ANALOGUE
SOFTCOPY
Advantages of softcopy photogrammetry
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A fully digital environment using digital images and producing digital output in an interactive and
automated fashion
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No constraint of focal length bracket as in analogue system
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Integration with Remote Sensing facility , real time data updation
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3 D graphical superimposition
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facility for automatic feature extraction
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No repetitive IO,RO, AO
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3D image file created against 2D in case of analogue
Planning
1 manday
Nil
Observation
2 mandays
4 hours
Adjustment
0.5 manday
2 hours
Feature extraction
3 days
3 days
Dtm
-
2 hours
Orthophoto
-
1 hour
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OUTPUT FROM SOFT COPY
The Exterior orientation parametres
Image ID Xs Ys
Zs OMEGA PHI KAPPA
1
2585692.8689 740124.8557 3787.3731
-0.2479 0.0405 -0.5047
2
2586684.0215 740116.1491 3787.0275
-0.3291 0.1346 -0.6047
3
2587673.7487 740088.5288 3789.4049
-0.0879 0.0749 -0.6678
4
2588649.2129 740077.9575 3787.7452
-0.1968 0.3647 -0.5568
5
2586093.6431 738381.9130 3762.2893
-0.6634 -0.1805 -1.5918
6
2586987.6281 738357.3513 3757.0480
-0.3535 -0.2078 -1.4326
7
2585355.5003 736806.1994 3729.8181
0.0835 -0.2224 -2.3031
8
2586405.7754 736787.5873 3731.5439
0.8881 -0.0061 -2.7211
The interior orientation parametres
of photos
Image Id f(mm) Xo(mm) Yo(mm)
1
304.9870 0.3300
0.0160
2
304.9870 0.3300
0.0160
3
304.9870 0.3300
0.0160
4
304.9870 0.3300
0.0160
5
304.9870 0.3300
0.0160
6
304.9870 0.3300
0.0160
7
304.9870 0.3300
0.0160
8
304.9870 0.3300
0.0160
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The residuals of the control points
Point ID rX rY
rZ
2
-0.2206 -0.6385 -1.4871
3
0.0000 0.0000
0.0000
4
-0.0814 0.4603 0.1124
5
0.0289 0.6508
-1.5084
6
0.1780 0.8125
-2.4390
7
0.1849 1.1825
-2.2830
8
-0.1343 -0.7684 0.0272
aX aY
aZ
-0.0064 0.2427 -1.0825
mX mY
mZ
0.1414 0.7263
1.4958
The coordinates of object points
Point ID X Y
Z Overlap
2 2585352.7900 735939.1620
482.2750 2
3 2588742.9990 739105.8140
503.7300 1
4 2586130.0920 737343.3800
494.6030 4
5 2588421.0920 740996.2110
513.2320 2
6 2588501.4130 740925.3480
511.4850 2
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 OUTPUT FROM ANOLOGUE SYSTEM
STATISTICS
1-
FOLD POINTS = 26
2-FOLD POINTS = 25
3-FOLD POINTS = 3
4-FOLD POINTS = 1
NUMBER OF BLOCK POINTS = 55
OBSERVATIONS FOR HORIZONTAL BLOCK = 128
UNKNOWNS FOR HORIZONTAL BLOCK = 92
REDUNDANCY FOR HORIZONTAL BLOCK = 36
OBSERVATIONS FOR VERTICAL BLOCK = 100
UNKNOWNS FOR VERTICAL BLOCK = 73
REDUNDANCY FOR VERTICAL BLOCK = 27
ROOT MEAN SQUARE VALUES OF THE RESIDUALS IN M
MODEL POINTS
RMS MP X = .208 NRES X =
56
RMS MP Y = .428 NRES Y =
56
RMS MP Z = .192 NRES Z =
56
PROJECTION centreS
RMS PC X = .360 NRES X =
12
RMS PC Y = .385 NRES Y =
12
RMS PC Z = .288 NRES Z = 12
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 CONTROL POINTS IN THE MODEL
RMS CM X = .333 NRES X =
11
RMS CM Y = .522 NRES Y =
11
RMS CM Z = .204 NRES Z = 11
CONTROL POINTS WITH WMN. 1
RMS CP X = .396 NRES X =
8
RMS CP Y = .431 NRES Y =
8
RMS CP Z = .229 NRES Z = 8
CONTROL POINTS WITH WMN. 2
RMS CP X = .000 NRES X =
0
RMS CP Y = .000 NRES Y =
0
RMS CP Z = .000 NRES Z = 0
CONTROL POINTS WITH WMN. 2
RMS CP X = .000 NRES X =
0
RMS CP Y = .000 NRES Y =
0
RMS CP Z = .000 NRES Z =
0
SIGMA NAUGHT IN M
SIGMA NAUGHT FOR HORIZANTAL BLOCK = .655
SIGMA NAUGHT FOR VERTICAL BLOCK = .399
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3D image file created against 2D in case of analogue
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Direct DTM file created i.e Contour are generated automatically
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The size of cursor may be bigger or smaller or colour can be changed
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Data collected in ground terms facilitate map compilation in any
scale.
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No high precision optical mechanical components thus regular calibration nor required
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Less office space required
CONCLUSION
All the SOI publications are output from Analogue system only. If we analyze a topo sheet we find
that all the features are collected from Analogue plotter. After
the development of analytical plotter, it also could
not replace the existing systems.
Almost all the operators in SOI are trained in Analogue system. As far as Photogrammetry society is
concerned we stand at the top. As far as accuracy is concerned there is no challenge to this technology.
Now technology is changing very fast. We have to adopt the latest technology. Today’s need is not
only a map but to have other related geographical information. Our old way of publication will not help for fast
changing environment. Therefore we have no way but to adopt latest technology i.e. Softcopy Photogrammetry
system to keep at pace with society’s need.
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