PRECISION INCREASE IN CLOSE - RANGE PHOTOGRAMMETRY
BY USING GEODETIC DATA
M.Orhan ALTAN
Technical University of Istanbul
Department of Geodesy and Photogrammetry
Ayazaga, ISTANBUL - TURKEY
Paper presented to Commission V
ABSTRACT
In close range applications the accuracy of obtained coordinates depends
at a great extend to the number of pass-points and camera configuration.
The aim of this study is to check the precision increase by using geodetic data with different number of pass points. The used data is derived
from a precise test-field, which was established with the use of girder
plates of a photogrammetric plotting instrument.
V ... 151
INTRODUCTION
The main task of photograrnmetric measuring techniques is to reconstruct
the spatial geometry of objects by means of photographs. The three dimensional coordinate determination is a part of this task, other than the
determination of the continous forms of the objects, such as contour
lines, profiles or cross sections. Then the last properties can also be
determined in some way from the three dimensional coordinates of the
object. Therefore, like the geodetic point determination, photogrammetric point determination plays an important role in all applications.
In 'this context, digital techniques have been used in photograrnmetry
since the 1960's, starting with aerial triangulation. With the use of
computer techniques and combined with data acquisition, the application
field of photograrnmetric methods is not limited to map production. The
use of analytical photogrammetry in engineering has become widespread,
so that one can very easyly speak of an engineering photogrammetry, a
discipline whose tasks become more and more
im~ortant.
During all these years the geometrical concept which is at the basis of
photogrammetric has changed considerably : the photograrnmetric stereo
model is replaced by the photograrnmetric bundle. The object points are
registered slmultaneously by the bundle of spatial directions from
camera stations. The accuracy of a single ray of a camera depends in
the first place on the principle distance c of the camera and on the
accuracy
of the image points coordinates.
V-152
The aim of this study is to test the accuracy increace by means of
some geodetic data specially in close range applications.
TEST FIELD
A test-field which was constructed for a different study /2/ gives a
good possibility to gain suitable data for this study, too. The test
field was constructed with twO girder plates. As
kno~m,
each of the
plates has in intersection of horizontal and vertical lines 100 points,
whose coordinates were determined with an accuracy of
/k
Girder
x
~
0.5
~m,
absolutly
plates
bar
Aluminium
y
y
\.1
I
Alum; nium
plate
I
I
I
I
125 9
I
~
"lI0~1
~
~
~/
I
( b)
(Q)
Camera stations
Figure 1- Desing of the test field with camera stations and exposure
directions, (a) view, (b) plane
V ... 153
As the photographic record of photogrammetric bundles are very easy
(free stationing), any camera station my be chosen in the field
(picture n-tupel). The bundles are only tied together by common object
points. As for the orientation of the bundles no restrictions are made,
and the pictures are taken sometimes freehand.
Depending on the problem the bundle block adjustment is erther carried
out as a free adjustment or if the coordinates are known for some object points - as an adjustment with control points.
Besides the spatial directions of the bundles and rays, other measurements and information can be included in the bundle block adjustment /1/
- distances (e.g. levelling rod fixed to the object.)
- absolute spot height or spot height differences (e.g. levelled points).
- shape conditions (such as several points on perpendicular line or in
a horizontal plane).
All of these possibilities, which was offered by analytical methods
enlarges the application areas of photogrammetric methods. Meanwhile
sophisticated software has been developed for bundle block adjustments.
But there isn't any detailed accuracy and reliability models besides
some attempts. (Altan 1984).
Specially there exist any theoretical or experimental study for an
accuracy model in the field of precision increase by means of geodetic
measurements which can be included to the mathematical model of photogrammetric data exquisition.
V-154
to a point and axes system in the surface plane of each plane. (Fig. I).
As the girder plates are mounted on an aluminium plate forming an angle
of 160 g between, the points form a three dimensional test field. All
coordinates of the test-field points are determined with an accuracy
of ±
12~m.
These about 200 points allows us now to determine some
geodetic information and to investigate the gain in accuracy by using
them.
PHOTOGRAMMETRIC SURVEY and GEODETIC DATA
This test field is photographed from three different camera stations,
with a mean object distance of about 60 cm. The image coordinates of
the girder points are measured in a Zeiss Stereocomparator. The geodetic information is obtained from the geotedic coordinates of two
points and for the calculations, four types of geodetic observation
is considered (see. Fig.2.)
V-155
~
v
v
5
/,-"'"
5
/'
./
.6h~
-
..,/./
....
5
J"\
v
5
Type I
'"
?I ilh
.t
cf ilh
Type II
'oJ
5
q
5
9
ll.h\ I/~h
9
5
Llhl
./
5
~
"Ah ,~
"".0
../ / Llh
5
5
Type III
Type IV
Figure 2. Different types of geodetic data corr.bination.
Type I, two distances
T)~e
elevation differences
Type III, two distances and four
elevation differences
Type IV four distances and two
II, two distances and two
elevation differences.
For the computations a computer program for a rigid bundle solution
was used, which permitts to add the geodetic measurements into the
calculations.
The base for further investigations are the 3- dimensional coordinates
of all test-field points, which result on one hand from the rigid bundle
solution and on the other hand the coordinates of these points achieved
by means of geodetic measurements. For the presentation of the results,
the differences of the coordinates of all points, which are represented
by the mean values, are considered.
V ... 156
MDX -
1
-n
IDXI
MDY
-
-n1-
IDyl
MDZ
-
1
-n
IDZI
with DX, DY, DZ
differences of the coordinates
and
number of points in the comparison.
n
For a better representation of results, the calculated values of MDX,
MDY and the ratio of MDZ to a mean object distance about 60 cm in per
mile are given as drawings in Fig. 3. These results are computed for
two different ratios of mean object distance to the depth of pass points
as two different versions. The first version is computed for the maximum
of control point depth (6.2 em) and the ratio of these value to the mean
object distance (60 cm) is 9.7 . The other version is computed for a
depth of 5 cm. The four types of geodetic observation are compared with
the results of photogrammetric data without geodetic data and as the first
two types doesn't bring any convenient change in the results, only the
combinations type III and type IV are shown in the drawings. The MDX,
and %oE values are given for different number of pass points,
from 3 pass points.
V ... 157
~IDY
beginr!i"'~~~
MDX
mm.
0.1
VER II
0.1
0-_
-0- - -0- - -0- - -0- -
-0- - -0- - -0- -
-0- ~0
VER ll+Typ 1lI
VER 1
0-
0.07
-:::-.:-:-s=--=-<>----o--o---c>----o_.....o.----(:>--Lo
11
10
5
3
VER I
12
+
Typ III
Number of
Pass points
MDY
mm.
0.2
VER II
0.1
-- -0- -
-o~-0
VER 11
+
Typ III
VER 1
0.02
'-~
5
VER J + Typ 111
10
Number of
Pass Points
°'00 E
0.115 0....-.
0.10
VER 1I
- 0 - --0-__
--0-
/
--0---0-
~
--0-- -0---0-,,-0
VER 11 • Typ HI
0.05
/ VER J
,\---0
0.0125
'\ VER 1. Typ III
2
3
5
10
fig. 3.1 Variation of MDX. MDY and
"00
11
11
Number of
Pass Points
E In the 6eodetic information Typ III
V ... 158
MDX
mm.
0.2
VER II
/
0 _____
0.1
0---0-_
-0- --0-- - 0 - - -0--
-O---O-~OVER II ... Typ IV
--O-__~__~--~--~~~--_o--_o~~~VER J
~ VER+Typ IV
0.02
0-_ - 0 - - - 0 - - - 0 - - - 0 - - -
3
4
5
10
11
12
Number of
Pass Points
MDY
mm.
0.2
0.1
'
0.01 -
- - -0 VE R
3
4
10
5
11
12
I + Ty P IV
Number of
Pass Points
0.125
0.10
0-
VER II
- -0.....,
'-0- -
-0- - ---0-.
-
-0-_ -0- - -0- _
-0-
'
-0
"\ VER II
+
Typ IV
0.05
0.012
10
fig. 3.2 Variation of MDX MDY and
I
8'00
V-159
11
12
Number of
Pass Points
E in the Geodetic informa1ion Typ IV
From the course of the curves one can see that the geode tie observation
gives only better results up to the 6 number of pass points. It is not
shown by the graphics but the types of Geodetic Information I and II
deosn't give any significant change in the accuracy.
CONCLUSIONS
In this work, it is tried to investigate how the geodetic information
can give an improvement in the accuracy of photogrammetric point determination. Therefore the data, which was obtained by the test-field was
used. It has shown, that in case of lack of pass point (less than 6)
geodetic data can help to increase the obtained accuracy.
REFERENCES
/1/ KRAUS, K.
Modern Photogrammetric Technology Facussing Civil
Engineering, Photogrammetria, 41, 1986, S.31-41
/2/
ALTAN, M.O.
A Super Precise Test Field For Close-Range
Photogrammetric Applications, Proc. of ISPRS,
Vol.26, Part 5, 1986, S.1-6
/3/
ALTfu~,
M.O.
Genauigkeitsuntersuchung Photogrammetrischer
Deformationsmessungen an einem Testfeld, Bul 52,
1984, 1.
V-160