Geometric correction of NOAA AVHRR imagery with few GCPS
Geometric correction with few GCPs
The test imagery was taken by NOAA AVHRR on December8, 1986 (UT). The size of imagery is (2048 Pixel x 4500 line).
The exterior orientation parameters were determined by eq.4 with 2 GCPs. In this case, the RMS error of 6 verification points was less than 1.6 pixels.
These cubic polynomials were shown in Fig.1 from this graph, it is possible to approximate each exterior orientation parameter by quadratic polynomial. Therefore, the orientation was carried out using quadratic polynomials with 9 GCPS. On the same 6 verification points, the error was less than 2.3 pixels.
When the number of GCPs is less than 9 in the imagery, it s necessary to decrease unknown coefficients. On this consideration exterior orientation parameters were determined with GCPs less than 9. However in this test imagery, computation was not converged, perhaps this imagery (x,y) or terrestrial object (X, Y, Z) has error. And least square method has problem with few data.
Conclusion
At this state, we analyzed exterior orientation parameters with few GCP. As a result, number of GCP can be decreased using quadratic equation. But exterior orientation parameters cannot be determined with less than 9 GCPs. The further study has to be carried to reduced with less than 09 GCPs. The further study has to be carried to reduced the number of GCPs to be less than 9 points. The idea are :
- Compute exterior orientation parameters with weight given GCPs
- Computer exterior orientation parameters using imaginary correction except block adjustment.
Fig.1 Orbit of satellite
Fig.2 Location and attitude of satellite
