Research on the geometric model of the aeroscanning images
Li shukai, Liu tong and Zhou lihua
Institute of remote sensing application, academia sinica
Abstract
In the past, the geometric problems of the aeroscanning images are mainly focused on the geometric errors and possible adopted models, at home and abroad. It is exceptional for practical models and results. This study begins from analysing the geometric characteristics of the aeroscanning images (MSS), the, using the aided data to set up control correcting model. The mean square error of the method of multinomial.
The matching mean square error of control points between the synchronous scanning images and the aerophotographs reaches two pixels. If improving a little accuracy of synchronism and shooting the time interval of synchronism, it is possible to obtain the result that the residual mean square error is less than one pixel.
Introduction
With the improving of band selecting level of sensor and the developing of hard equipment of the data canal, the areoscanning images brought more rich and more important resources information. But, because the changes of state and position of platform during flight are larger than that of satellite, the unlinear geometric deformation of the aerial images are sore serious than that of satellite scanning image, it is more difficult to make geometric processing than satellite image. At present the simulated geometric processing of aeroscanning image is still a problem.
This study begins from analysing the geometric characteristics of the aeroscanning image. We adopted various model tests to compare and analyse, the best model is used as the foundation setting up geometric processing system.
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Aided data acquisition and processing
Known as previous described, the state angles (q,w,k) and the geographic position (xo, yo, zo) of projectional center are recorded during each scanning line scanning and collection date, it is not difficult to set up geometric simulation for aeroscanning images, this depends on the density and precision of recorder.
Now many technical means can be used to record the data as following: the record method of inertia navigation data matching with scannor; frame camera matching with scannor: arerial GPS matching with scannor etc. the first two methods are mainly discussed in this test.
Pyramid is carried with collineraity equation (1), tangent correction uses equation (2), cubic parameter splines uses equation (3),
(4).
Eq.1
Ys=fx. Tan ( (IRi-(IN+1) / 2) * b ---------------(2)
b: instaneous field of view
fx: equivalent focus
IN: the amount of pixel in one scanning line
IRi: the number of pixel
Eq.3
fo(t) = 1-3t*t+2t*t*t
f1(t) = 3t*t-2t*t*t
go (t) = t-2t *t+t*t*t
g1 (t) = -t*t+t*t*t
t= (x-xi / hj+1 ) , hj+1 = xj+1 - xj
xj, yj are the coordinates of control points, fo, f1, go, g1 are the harmonic function. Adding the condition of the second derivatives of the control points which are continuous:
Eq.
Adding the end condition
Eq.
The right side of equation are called as D1 and D2, combing bj (j=1, 2…..,n), they consist of n equations, these can be expressed with matrix:
Eq.4
