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Rational Polynomial Rectification

Papers Cited


QuickBird … Geometric Correction, Processing and Data.  by Phillip Cheng, Thierry Toutin, Yun Zhang, and Mathew Wood.  EOM, May 2003, pp. 24-30.

Block Adjustment of High-Resolution Satellite Images Described by Rational Polynomials.  by Jacek Grodecki and Gene Dial.  Photogrammetric Engineering and Remote Sensing.  Vol. 69, No. 1, January 2003, pp. 59-68.

Abstract:  “This paper describes how to block adjust high-resolution satellite imagery described by Rational Polynomial Coefficient (RPC) camera models and illustrates the method with an Ikonos example.  By incorporating a priori constraints into the adjustment model, multiple independent images can be adjusted with or without ground control.  The RPC black adjustment model presented in this paper is directly related to the geometric properties of the physical camera model.  Multiple physical camera model parameters having the same net effect on the object-image relationship are replaced by a single adjustment parameter.  Consequently, the proposed method is numerically more stable than the traditional adjustment of exterior and interior orientation parameters.  This method is generally applicable to any photogrammetric camera with a narrow field of view, calibrated, stable interior orientation, and accurate a priori exterior orientation data.  As demonstrated in the paper, for Ikonos satellite imagery, the RPC block adjustment achieves the same accuracy as the ground station block adjustment with the full physical camera model.”

Bias Compensation in Rational Functions for Ikonos Satellite Imagery.  Clive S. Fraser and Harry B. Hanley. Photogrammetric Engineering and Remote Sensing.  Vol. 69, No. 1, January 2003, pp. 53-57.

Abstract:  “A method for the removal of exterior orientation biases in rational function coefficients (RPC) for Ikonos imagery is developed.  These biases, which are inherent in RPC’s derived without the aid of ground control, give rise to geopositioning errors.  The 3D positioning error can subsequently be compensated during spatial intersection by two additional parameters in image coordinates.  The resulting bias parameters can then be used to correct the RPC’s supplied with Ikonos Geo imagery such that a practical means is provided for bias-free ground point determination, nominally to meter-level absolute accuracy, using entirely standard procedures on any photogrammetric workstation that supports Ikonos RPCs.  The method requires provision of one or more ground control points.  Aside from developing the bias compensation method, the paper also summarizes practical testing with bias-corrected RPCs that has demonstrated sub-meter geopositioning accuracy from Ikonos Geo imagery.”

Error Tracking in Ikonos Geometric Processing Using a 3D Parametric Model.  Thierry Toutin. Photogrammetric Engineering and Remote Sensing.  Vol. 69, No. 1, January 2003, pp. 43-51.

Abstract:  “Thirteen panchromatic (Pan) and multiband (XS) Ikonos Geo product images over seven study sites with various environments and terrain were tested using different cartographic data and accuracies with a 3D parametric model developed at the Canada Center for Remote Sensing, Natural Resources Canada.  The objectives of this study were to define the relationship between the final accuracy and the number and accuracy of input data, to track error propagation during the full geometric correction process (bundle adjustment and ortho-rectification), and to advise on the applicability of the model in operational environments.

“When ground control points (GCPs) have an accuracy poorer than 3 m, 20 GCPs over the entire image are a good compromise to obtain a 3- to 4-m accuracy in the bundle adjustment.  When GCP accuracy is better that 1 m, ten GCPs are enough to decrease bundle adjustment error of either panchromatic or multiband images to 2 to 3 m.  Because GCP residuals reflect the input data errors (map and/or plotting), these errors did not propagate through the 3D parametric model, and the internal accuracy of the geometric models is thus better (around a pixel or less).

“Quantitative and qualitative evaluations of ortho-images were thus performed with either independent check points or overlaid digital vector files.  Generally, the measured errors and a 2- to 4-m positioning accuracy was achieved for the ortho-images depending upon the elevation accuracy (DEM and grid spacing).  To achieve a better final positioning accuracy, such as 1 m, a DEM with an accuracy of 1 to 2 m and with a fine grid spacing is required, in addition to well-defined GCPs with an accuracy of 1 m.”

Rational Functions and Potential for Rigorous Sensor Model Recovery.  Kalchang Di, Ruijin Ma, and Rong Xing U. Photogrammetric Engineering and Remote Sensing.  Vol. 69, No. 1, January 2003, pp. 33-41.

Abstract:  “Rational functions (RFs) have been applied to photogrammetry and remote sensing to represent the transformation between the image space and object space whenever the rigorous model is made unavailable intentionally or unintentionally.  It attracts more attention now because Ikonos  high-resolution images are being released to users with only RF coefficients.  This paper briefly introduces the RF for photogrammetric processing.  Equations of space intersection with upward RF are derived.  The computational experimental result with one-meter resolution Ikonos Geo stereo images and other airborne data verified the accuracy of the upward RF-based space intersection.  We demonstrated different ways to improve the geopositioning accuracy of Ikonos Geo stereo imagery with ground control points by either refining the vendor-provided Ikonos RF coefficients or refining the RF-derived ground coordinates.  The accuracy of 3D ground point determination was improved to 1 to 2 meters after refinement.  Finally we showed the potential for recovering sensor models of a frame image and linear array image from the RF.”

3D Reconstruction Methods Based on the Rational Function Model.  C. Vincent Tao and Yong Hu.   Photogrammetric Engineering and Remote Sensing.  Vol. 68, No. 7, July 2002, pp. 705-714.

Abstract:  “The rational function model (RFM) is an alternative sensor model allowing users to perform photogrammetric processing.  The RFM has been used as a replacement  sensor model in some commercial photogrammetric systems due to its capability of maintaining the accuracy of the physical sensor models and its generic characteristic of supporting sensor-independent photogrammetric processing.  With RFM parameters provided, end users are able to perform photogrammetric processing including orthorectification, 3D reconstruction, and DEM generation with an absence of the physical sensor model.  In this research, we investigate two methods for RFM-based 3D reconstruction, the inverse RFM method and the forward RFM method.  Detailed derivations of the algorithmic procedure are described.  The emphasis is placed on the comparison of these two reconstruction methods.  Experimental results show that the forward RFM can achieve a better reconstruction accuracy.  Finally, real Ikonos stereo pairs were employed to verify the applicability and the performance of the reconstruction method.”

Updating Solutions of the Rational Function Model Using Additional Control Information.  Yong Hu and C. Vincent Tao.  Photogrammetric Engineering and Remote Sensing.  Vol. 68, No. 7, July 2002, pp. 715-723.

Abstract:  “The rational function model (RFM) is a sensor model that allows users to perform ortho-rectification and 3D feature extraction from imagery without knowledge of the physical sensor model.  It is a fact that the RFM is determined by the vendor using a proprietary physical sensor model.  The accuracy of the RFM solution is dependent on the availability and usage of ground control points (GCP).  In order to obtain a more accurate RFM solution, the user may be asked to supply GCPs to the data vendor.  However, control information may not be available at the time of data processing or cannot be supplied due to some reasons (e.g., politics or confidentiality).  This paper addresses a means to update or improve the existing RFM solutions when additional GCPs are available, without knowing the physical sensor model.  From a linear estimation perspective, the above issue can be tackled using a phased estimation theory.  In this paper, two methods are proposed: a batch iterative least-squares (BILS) method and an incremental discrete Karman filtering (IDKF) method.  Detailed descriptions of both methods are given.  The feasibility of these two methods is validated and their performances are evaluated.  Some results concerning the updating of Ikonos imagery are also discussed.”

A Study on the Generation of the Komsat-1 RPC Model.  Hye-jin Kim, Dae-sung Kim, Hyo-sung Lee, Young-il Kim. no date. 4 pages.  see http://www.isprs.org/commission3/
proceedings/papers/paper129.pdf

Abstract:  “The rational polynomial coefficients (RPC) model is a generalized sensor model that is used as an alternative solution for the physical sensor model for IKONOS of the Space Imaging.  As the number of sensors increases along with greater complexity, and the standard sensor model is needed the applicability of the RPC model is increasing.  The RPC model has the advantages in being able to substitute for all sensor models, such as the projective, the linear pushbroom and the SAR.

“This report aimed to generate a RPC model from the physical sensor model of the KOMPSAT-1 (Korean Multi-Purpose Satellite) and aerial photography.  The KOMPSAT-1 collects 510~730 nm panchromatic imagery with a ground sample distance (GSD) of 6.6 m and a swath width of 17 km by pushbroom scanning.  The iterative least square solution was used to estimate the RPC.  In addition, data normalization and regularization were applied to improve the accuracy and minimize noise.  This study found that the RPC model is suitable for both KOMPSAT-1 and aerial photography.”

Rational Mapper: A Software Tool for Photogrammetric Exploitation of High Resolution Satellite Imagery.  C. Vincent Tao, Yong Hu, Wanshou Jiang.  no date.  6 pages.  see http://www.geoict.yorku.ca/project/rationalmapper/rationalmapper.htm

Background:  “The Rational Function Model (RFM) has gained considerable interest recently in the photogrammetry and remote sensing community.  This is mainly due to the fact that some satellite data vendors, for example, Space Imaging, Thornton, CO, USA, have adopted the RFM as a replacement sensor model for image exploitation.  The data vendor will supply users with the parameters of the RFM instead of the rigorous sensor models.  Such a strategy may help keep the confidential information about the sensors and on the other hand, facilitate the use of high-resolution satellite imagery for general public uses (non-photogrammetrists) since the RFM is easy to use and easy to understand.”

Continues on with a easily understood description of the general idea.

An Update on the Use of Rational Functions for Photogrammetric Restitution.  Ian Dowman and Vincent Tao.  ISPRS.  September 2002, Vol. 1, No. 3.  pp. 22-29.

Extraction:  “During the past four or five years the photogrammetric community at large has become aware of the use of rational functions for photogrammetric restitution.  This has been due largely to the need to use these for setting up Ikonos data, as Space Imaging does not provide a physical sensor model with the image data.  Rational functions have been used for some time for military use and their widespread acceptance in that area has led to the proposal to the OGC for a standard for image restitution based on rational functions on the basis of its universality: it can be used with any sensor.”

For the complete article see: http://www.isprs.org/publications/highlights/highlights0703/ 22_HL_09_02_Article_Dowman.pdf

Geometric Information from IKONOS.  Zhigu Hu.  GIM International.  Vol. 17, No. 9, September 2003.  pp. 42-45.

“Since  pixel size of panchromatic IKONOS imagery is one meter it is desirable that the planimetric and height error after georeferencing be smaller.  Which method provides the high accuracy requirement?  The author tested three processing methods: (1) IKONOS RPC parameters only, (2) an associated adjustment of RPC parameters with control points and (3) a strict geometric model based on affine transformation.  The adjustment of RPC coefficients with one or two control points improves accuracy significantly, especially in elevation.  Using only five control points, the strict  model yields very high accuracy of 5 to 12 cm in X, Y, and Z with one pair of stereo images covering.  The method does not need RPC coefficients, whilst the coordinate system can be any independent one.  The strict model represents a new step forward, both in theory and application, for high-resolution IKONOS imagery processing.”

[In the first sentence of this paper the author states: “The stereo pair of panchromatic IKONOS images with 1-meter spatial resolution used in the test covers over 20 square kilometers of a quite flat Beijing suburb.”  It is possible that a DEM was not even used and the solution was performed using an average elevation.  How well will these results extend to areas with typical topographic relief?]

 

25 March 2009  

page update: 26 May 11


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