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# Full text

Title
New perspectives to save cultural heritage
Author
Altan, M. Orhan

CIPA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
Figure 4. Map sheet, scale 1/500
Up to now, around 17.000 ground points were captured to
produce the 1/500 scale map sheets.
4. DIGITAL ELEVATION MODELS (DEM)
Once a digital elevation model of a landscape is available, such
a model can serve as a base for many applications, like contour
line generation, volume calculation, visibility analysis,
calculation of cross sections and all other applications which
need a digital representation of the terrain as an input, like
virtual flights and walk throughs, for instance.
//Transformation mit 5 Passpunkten ( 1000,4000, 5000, 11U0U, 9000}
Arc: transform contours fivepp
Transforming coordinates for coverage contours
Scale (X.Y) = (0.997,0.999) Skew (degrees) « (0.081)
Rotation (degrees) « (-0.056) Translation = (-2710.751.-1121.360)
RMS Error (input,output) = (0.888.0.885)
Affine X - Ax + By + C
Y « Dx ► Ey * F
A = 0.997 B = 0.002 C = -2710.751
D = -0.0C1 E * 0.999 F - -1121.360
tic id input x input y
output x output y x error y error
1000
5000
4000
11000
9000
Arc :
12727.471
10000.00C
11485.780
8760.518
11516.838
8790.385
13955.460
11221.840
13001.104
10272.820
11147.184
10000.000
10911.637
9766.446
10067.302
8922.818
11076.767
9928•892
10980.450
9833.549
-0.662
0.864
-0.073
1.068
-1.196
0.308
-0.191
0.057
-0.125
-0.049
Table 2. Results of an affine data set transformation
from the paper map and ending in the data fusion with data sets
obtained from independent field surveys.
4.2 Handling of Concurrent Information
The 1/5000 scale paper maps cover a much larger area than the
1/500 scale maps do. The smaller scale maps enclose the actual
research area. Following the progress of the archaeological
research digital elevation information for more and more parts
of the research area will be captured in future by tacheometric
high quality measurements. This procedure of continuously
extending the ground survey unavoidably will result in
concurrent and possibly in contradictory elevation information
as compared with the already available digital elevation
information obtained from the paper maps. In our case we
assume the accuracy of the ground survey results to be
substantially higher than the paper map results. Thus, we
decided to supersede paper map results by ground survey results
whenever a ground survey was available.
4.3 Quality Checks
In our area there are mainly two sources of digital heights
available, namely the results of the tacheometric field surveys
and a set of 1/5000 scale paper maps (Siebold, 1998). Both
sources were used to create a Triangular Irregular Network
(TIN). Three-dimensional point co-ordinates were taken from
the tacheometrically measured ground points and from digitised
contour lines of the paper maps, respectively. When performing
the fusion between these two data sets several items have to be
4.1 Common spatial reference frame
The local reference frame (see section 2) was to be used as the
one common base system for all data sets. That is why, in a first
step, all data sets available in other reference systems had to be
transformed into that target system. For the results of the
tacheometric surveys this task could be easily performed by
using a set of common reference points which were used in all
field campaigns in the same way. The TIN’S which had been
generated from the paper maps were transformed by using a set
of points on the maps which could be identified in the field.
Table 2 shows the residuals of a redundant affine
transformation with 5 control points. As can be seen the root
mean square error is in the range of 1 metre, which equals 0,2
millimetres in 1/5000 map scale, a satisfying measure which
proofs the quality of the whole data conversion process starting
The concurrent elevation information available in all areas
covered by ground survey results so far was used for an in
depth quality check by analysing the differences of heights
calculated from the concurrent TIN’s: Heights for the complete
set of around 17.000 tacheometrically measured 3D points were
calculated from the paper map TIN. If one compares these
calculated heights with the tacheometrically measured point
heights one gets a sound insight into the properties of both data
sets. Figure 5 shows the spatial pattern resulting from a
classified plot of height differences. As one can see a striking
fact is that the hillocks (Buyukkale, KUctikkale, Zegreg Tepe
and others) in general show positive height differences against
the pseudo true values of the ground survey TIN. This means
that the heights calculated from the paper map TIN are lower
than the heights obtained from ground surveys in that areas. In
other areas we have to do with the opposite facts: the heights
obtained from the paper map TIN are larger than the ground
surveyed heights. Both facts can be explained: in the paper
maps sometimes there were no spot heights available at the top
of a hillock, which means, that the contour lines with the
highest locally available height numbers define the top. The
remaining height difference up to the real top of the local
hillock is missing, whilst it is present in the ground survey data.
The fact that there are areas where the surface of the paper map
TIN is located systematically above the real ground surface
may be caused by the map production process: data automation