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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part BS. Istanbul 2004
UMK CANON D30
FAÇADE CP CP DIST A (CP) A(DIST) B (CP) B (DIST)
rms XY (mm) 427 +59 +120 + 64.9 +770 + 54.9 + 66.9
| rms Z (mm) t 3.4 99 t 16.8 +579 + 105.0 + 58.6 +1126
max Vxy (abs) (mm) 3.0 7.9 14.2 85.3 93.8 74.2 82.5
max Vz (abs) (mm) 5.0 14.5 26.9 85.6 208.4 82.2 -224.5
Prop.accuracy XY 1:570 1:2600 1:1300 1:230 1:200 ]:275 1:22
Prop.accuracy Z 1:3200 1:1200 1:700 1:200 1:110 1:200 1:100
Table 4
Facade case: rms errors, maximum residuals (in absolute values) and proportional accuracies in XY and Z for different
situations. UMK: stereopairs oriented with control points (CP); Canon D30: stereopairs oriented with CP; known
distance (DIST); A: stereopairs oriented with CP and DIST (only calibrated principal distance is used); B: stereopairs
oriented with CP and DIST (no camera calibration).
Again the camera was considered as calibrated, but, since
control point and convergent photographs were not used,
systematic errors have been propagated to object space and
the accuracy has decreased almost 50 % (mean and
maximum errors of + 1.5 cm and + 3 em, respectively).
Finally, other situations were explored. In the case À (Table
4) only principal distance was known (distortion and
principal point offset were neglected). This option was
selected because principal distance is casy to be calibrated,
even with graphical methods. But in case B any calibrated
inner parameter were considered (the principal distance was
the nominal focal length, 20 mm). In both cases, A and B,
orientations were carried out with control points (CP) and a
known distance (DIST). In the four situations (Table 4) the
results were very weak (with maximum errors higher than +
20 cm), with slight better results in the case of using control
points (as expected). There were not meaningful differences
in calibrate only the focal length or not calibrate at all. In
stereopairs, errors in the focal length can be partially
compensate with changes in the projection center, so it is an
error source less critical than distortion in this lens type or
other systematic errors present in non metric cameras.
5. CONCLUSIONS
As conclusion, the Canon D30 camera has revealed to be an
effective data acquisition system for low and medium
precision works in archaeological and architectural surveys.
The test with wide angle and normal lenses have shown that
camera calibration at laboratory and the use of control points
can minimize the systematic errors present in non metric
cameras when stereopairs are used. If the photogrammetric
network is appropriate a field self calibration can improve the
final accuracy. The experiences have shown that errors
between 5-10 mm can be reached at object-camera distances
up to 15 m. (longer distances have not been tested) even in
the case of single stereopairs. So the Canon D30 can be used
for conventional architectural and archaeological surveys
including stereoplotting, DSM, ortophotographs, rectified
images, 3D modeling, but also control point network
densification. Future work will be focusing in test some
improvement with self calibration and additional parameters,
tests at longer distances and the evaluation of similar present
digital cameras with higher resolution.
REFERENCES
Atkinson, K.B. (ed.), 1996. Close Range Photogrammety and
Machine Vision. Whittles Publishing, Scotland, U.K.
Canon, 2004. Canon Europe web page. http://www.canon-
europa.com/ (accessed 20 April 2004)
Fryer, J.G., 1992. Recent developments in camera calibration
for close range applications. In: ZAPRS, Washington, USA.
Vol. XXIX, part B5, pp. 594-599.
Mata, E., Cardenal, J., Castro P., Delgado, J., Hernandez
M.A., Perez, L.L., Ramos, M., Torres, M., this volume.
Digital and analytical photogrammetric recording applied to
cultural heritage. a case study: “St. Domingo de Silos’
Church (XIV" century, Alcala la Real, Spain)" In: The
International Archives of the Photogrammetry, Remote
Sensing and Spatial Information Sciences, Instabul, Turkey,
Vol. 34, Part XXX.
Ogleby, C, Papadaki, H., Robson, S., Shortis, M., 1999.
Comparative camera calibrations of some "off the shelf"
digital cameras suited to archaeological purposes. In: JAPRS
Photogrammetric Measurement, Object Modelling and
Documentation in Architecture and Industry. Thessaloniki,
Greece. Vol XXXIL Part 5W11, pp. 69-75.
Trinder, J.C., Jansa, J., Huang, Y., 1995. An assessment of
the precision and accuracy of methods of digital target
location. ISPRS Journal of Photogrammetry and Remote
Sensing". 50 (2), pp.. 12-20.
UJA, 2003. Trabajos fotogrametricos y topometricos de
generacion de cartografia para la rehabilitacion de la Iglesia
de Santo Domingo de Silos (Alcala la Real, Jaen). Technical
Report, University of Jaen (UJA), Spain.
ACKNOWLEDGMENTS
This research was partially supported by the Town Council
of Alcala la Real (Jaen, Spain) and “Sistemas
Fotogrametricos y Topometricos” Research Group (TEP-213;
Junta de Andalucia, Regional Government).
