1) The Westin model with 7 parameters as originally articulated is not
adequate in modelling the SPOT dynamic system. Severe disturbances
were noticed in a points field of more than 17 GCPs. After excluding
all other options for the source of this problem, an extra parameter was
added. A linear parameter in phi showed the highest sensitivity,
removing the misfits to the points field. Incidentally, this was the only
linear rotational parameter used in the model developed by Gugan.
2) Using seven well spaced control points, this model consistently
showed RMS errors just above one pixel pixels at check points. With
more GCPS this stabilizes in the one pixel region (see figures and
tables Sa-5d above). When corrected for the error in the control
network, RMS errors is below one pixel. Misclosures have been
calculated using a single bundle resection without employing the stereo
view; a stereo intersection could substantially dilute the misclosures
and hide disturbance in the points field.
3) While the integrated attitude measurements taken from the SPOT
header may not model platform attitude adequately, removing these
measurements from the model consistently resulted in a slight
deterioration of results.
4) It was also found that components of a 2nd-degree phi are present in
the SPOT model, but to a lesser extent. The best results were achieved
using a linear and quadratic rates of change for Phi but subtracting the
attitude changes in phi calculated from the integrated attitude velocities
recorded in the SPOT header files; and adding kappa and Omega
attitude changes. This approach was inspired by Priebbenow.
5) When results are compared with earlier work , it would seem that
less than 8 parameters are inadequate to model SPOT precisely. This
SPOT model is robust and converges rapidly in 4 iterations.
6) Using the same control points on the two stereo images gives the
best stereo viewing; this may not always be feasible for images with
small overlap areas. Relative orientation is no problem using a large
number of good quality, well spread, GCPs (>12) (that are not the same
on each image) covering the images.
7.0 BIBLIOGRAPHICAL REFERENCES
[Dowman LJ. Neto E. Veillet L, 1991] "Description of Test and
Summary of Results", Test o Triangulation of SPOT Data, OEEPE
official publication No. 26, Editor Dowman I.J., August 1991.
[Galguly, P.K. 1991] "Mathematical Modelling for Mapping From
SPOT," Unpublished MSC thesis, ITC, Enschede, Nederland, 1991, 89
pages.
[Gugan, D.J. 1987] "Topographic Mapping from SPOT Imagery", PhD
Thesis, University College London, pp 253 pages, 1987.
[Gugan, D.J. and Dowman, LJ. 1988] "Topographic Mapping from
SPOT Imagery", Photogrammetric Engineering and Remote Sensing,
Vol. 54, No. 10, October 1988, pp 1409-1414.
[Konecny, G. 1987] "Geometric Evaluation of SPOT Imagery,"
CERCO seminar on the SPOT system and its applications, Paris,
September 6-9, 1988, pp 20-53.
[Kratky V. 1987] "Rigorous Stereophotogrammetric Treatment of
SPOT Images", SPOTI - Utilisation des Images, Bilan, resutáts, CNES,
Paris, pp. 1281-1288.
[Cogan, Hinsken 1992] “The Concept of a Photogrammetric
Workstation Outlined by the Example of the Leica SD2000" ;
International Archives of Photogrammetry and Remote Sensing, Vol.
XXIX, B2, pp. 596 - 600, Washington 1992.
[Hinsken, Meid 1993] The Use of Leica's Universal Analytical
Photogrammetric Workstations for Close Range Applications" ; in
"Optical 3-D Measurement Techniques II", Papers presented to the
conference organized at Zurich/Switzerland, October 4-7, 1993 ;
Wichmann Verlag, Karlsruhe Germany, 1993.
[Mikhail E.M (with contributions from Ackermann F.) 1976]
"Observations and Least Squares". New York: EIP; xi, 497 pp: 1976.
[NASA 1993] Document NP-202, EOS Reference Handbook 1993.
590
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B3. Vienna 1996
airborne and spaceborne imagery", PHD theses, University College
London, still in progress.
[Priebbenow and Clerici 1988] "Cartographic Applications of SPOT
Imagery" Proceedings of ISPRS Congress, Commission IV, 1988.
[Radhadevi P.V., Sasikumar T.P., Ramachandran R. 1994] "Orbit
Attitude Modelling and Derivation of Ground Co-ordinates from SPOT
Stereopairs", ISPRS JOURnal of Photogrammetry and Remote Sensing,
49(4): 22-28, 1994.
[SPOT 1995] "A Catalogue of SPOT Products", SPOT IMAGE,
Toulousse, Cedex, France, 1995.
[Westin T. 1990] "Precision Rectification of SPOT Imagery", PE&RS,
Vol. 56, No. 2, pp. 247-253, February 1990.
[Nwosu A.G. 1996] “A Generic approach towards camera modelling of
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