| 25 | | 11th Mar. 2008: Note that the email below were the numbers as originally received, but calculation of the Gamma angle contains an error - "gam = acos( abs(dz) / dst )" should use asin, not acos. Del and Dst are unaffected. Investigation of this suggests this causes an along-track error of approx. 1.5m in all 2006/2007 delivered data for ATM, which may be partially corrected by boresight correction (since these numbers were computed using the incorrect lever-arm numbers) depending on flight altitude. Other sensors have smaller errors, since the effect of the original calculation error is smaller for the offset angles of these sensors. Correct lever-arm numbers are below for reference, new boresight numbers would need to be computed to use these. |
| | 25 | 11th Mar. 2008: Note that the email below contains the numbers as originally received, but calculation of the Gamma angle contains an error - "gam = acos( abs(dz) / dst )" should use asin, not acos. Del and Dst are unaffected. Investigation of this suggests this causes an along-track error of approx. 1.5m in all 2006/2007 delivered data for ATM, which may be partially corrected by boresight correction (since these numbers were computed using the incorrect lever-arm numbers) depending on flight altitude. Other sensors have smaller errors, since the effect of the original calculation error is smaller for the offset angles of these sensors. Correct lever-arm numbers are below for reference, new boresight numbers would need to be computed to use these. |