CIPA 2003 XIX 11 ' International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
Defining the limits of the top surface of the upper
most deposit
Unique numbering of the top surface and the de
posit (s004, d004)
Photographic record
Measuring ground control points
Measuring boundary polygon and topography of
the top surface
Excavating the deposit, taking samples, measur
ing find and sample coordinates, describing de
posit, describing finds
Unique numbering of the bottom surface (b004)
Photographic record of the bottom surface
Measuring ground control points
Measuring the topography of the bottom surface
The process of recording of interfaces is as follows:
Unique numbering of the interface (¡004)
Photographic record of the bottom surface
Measuring ground control points
Measuring the topography of the bottom surface
Describing the interface
The stratigraphic relations of the top surface the deposit
and its bottom surface are trivial. The stratigraphic rela
tions of any top surface, bottom surface or interface have
to be observed and recorded. Find and sample records,
descriptions and stratigraphic relations are recorded on
pre-printed sheets or directly in a database on site refer
enced by the unique number of the unit of stratification.
5. INTERFACING TO THE GIS
To be able to use the digital photographic record in the
GIS, it has to be rectified and georeferenced. We had been
running extensive tests to find a fast and easy way to rectify
the digital image within an accuracy that would not exceed
+/- 5 cm. During these tests, we realized, that to stay within
this range of accuracy, a combination of vertical photo
graphs and a projective transformation of the image would
be sufficient in most cases. The use of a projective trans
formation assumes, that the topography of the surface is
relatively flat. The plane of the surface is defined by at least
4 ground control points, which must be well distributed
around the surface to be recorded. They are measured in
2D space and define the parameters of the transforma
tion.
This simple method of rectification could yield reasonably
good results as long as the surface has minor differences
in height or is evenly sloping up (Figure 1). The issue gets
more problematic, when the topography of the unit of strati
fication is rough, having large height differences on sev
eral locations. In this case an accuracy within +/- 5 cm
cannot be guaranteed. To solve this problem, more con
trol points have to be added defining smaller plane units
within the surface, which then are rectified individually. The
transformed parts are mosaicked together again in GIS.
Another possibility would be to use software capable of
differential rectification using a DTM, as we did in our tests.
So far, the procedure of rectification is done using the soft
0 025 0.5 0.7S _ 1 125
Figure 1: Comparison using a stratification unit with
a height difference of 25 cm within an area of 1 m.
White lines: visible artefacts drawn from
photogrammetri'cally produced orthophoto (maxi
mum error +/- 1.5 cm).
ware “Monobild” (http://www.geosi.at/produkte/monobild/
monobild.htm). It is an easy to use software designed for
our needs.
To be able to automatically import and analyse the spatial
data in ArcView GIS, the extension module ArcDig was pro
grammed using Avenue, the object oriented programming
language of ArcView 3.2. The import routine reads the na
tive ASCII data file format of the geodetic instrument and
converts the data into the native shape file format of ArcView.
The measurements of the boundary polygon are stored
as a 2D polygon shape and as a 3D polyline shape. The
3D mass points of the surface and optional breaklines are
imported as points respectively lines. Finds and samples
are imported as points, where the numbers of the finds
are automatically added to the database connected with
the shapefiles. Ground control points are written to ASCII
text files - one file per unit of stratification. The format is
fitted to the needs of the import function of the rectification
software.
Figure 2: Graphie raw data of stratification unit s059
in Schwarzenbach after import.