10.2.4 Elimination of faulty measurements
Thorough knowledge of Section 2.3 is essential; the methods described there support the detection of measurement errors. The greatest errors are marked in the list by stars. These stars may conveniently be used as a search argument in EDITOR, in order to detect formal errors (Chapter 7) or faulty measurements.
During determination of the number of stars contained in the photo measurements, all photo measurements of a point will be regarded as a unit. The stars will only be computed for the greatest normalised residual, and then will be allocated to the series of photo measurements for this point. For all other types of observations, each observation will be treated separately.
When the data-snooping option is activated, a value ∇li is derived and printed for those observations with the test value w exceeding 2.0, or those which obtain at least one star (see equation 2.3.2/8).
Examples for output of residuals with activated data-snooping:
Residuals of photo coordinates list limit = -1.0 * sigma Point Photo Vx' Vy' Rx'% Ry'% Wx' Wy' Nabla x' y' ( 1 / 1 0 0 0 ) ( 1 / 1 0 0 0 ) ------------------------------------------------------------------------------------------- *** 4671 466 14.3 -13.7 14 46 4.2 -2.2 -101.8 29. 467 -29.4 -10.7 52 54 -4.5 -1.6 55.6 19. 468 14.6 23.6 12 38 4.7 4.2 -121.6 -61. 307 Cont.Pt. 2001 2.5 -2.4 50 53 0.6 -0.6 2002 -3.4 2.8 63 50 -0.7 0.7 3001 -3.9 -0.2 61 51 -0.8 0.0 3002 1.1 0.1 48 53 0.3 0.0 Residuals transformed to object space (1/1000) 2001 18. -16. 14. 2002 -31. 25. -4. 3001 34. 2. 2. 3002 -8. -3. 3. RMS 25. 15. 7. |
The photo measurement of point 4671 in photo 468 is identified with a wx of 4.7 as measurement error. This measurement has to be removed and is therefore listed in the SKIP file.
Point 307 is a control point. In addition to the residuals of their photo measurement the spatial distance of every point to the phot ray will be listed under the header line “Residuals transformed to object space”. Unit of measure is 1/1000 of the original unit. In this case [mm].
*1 *2 Gross data errors detected by BINGO *3 *4 <______Point___><______Photo___><__LINE__><___Rays_><__Wi_/_Vi_> *5 SKIP 4671 468 0 3 6.3 SKIP 9111 9010 0 5 5.7 SKIP 8223 8023 0 5 5.6 |
After application of the program SKIP this measurements takes part in the next adjustment with the weight Zero.
Point 352 is a control point. In addition to the residuals of the photo measurements, the spatial distance of the adjusted coordinates of this point to every photo ray is listed under the headline "Residuals transformed to object space". Here the unit is [mm].
Errors in all other files have to be removed manually. The following shows a list example:
Residuals List limit = -1.0 * sigma Type No.1 No.2 Residual Rii% W Nabla L (1/1000) (1/1000) ------------------------------------------------------------------------------------------------ CONT X 324 91.7 33 2.1 * CONT Y 377 -183.3 59 -3.2 309.1 ** GPSA Z 2001 -7.7 6 -2.0 * GPSA X 2009 -13.2 4 -3.2 370.9 ** GPSA Y 2012 1.1 0 2.1 * GPSA X 2026 5.5 2 2.8 * GPSA X 3001 -1.3 0 -2.7 * GPSA Y 3002 -3.9 2 -2.1 * GPSA Y 3009 -0.8 0 -2.1 * |
All observations with a test value w > 3.0 should be eliminated if during variance-component estimation the test value T for the corresponding observation series does not indicate a model error (see Section 10.2.5). Faulty measurements should preferably not be removed from the data file, but care must be taken to ensure that they will be ignored by the program, with a preceding "*" in column 1.
Among the residuals of photo measurements (in the group of measurements of a point) certain groups of residuals are often distinguished by the same sign and very similar magnitude. Errors of pointing (different points in the various photos or models) can then be assumed. The photo measurements of such a sub-group should then be combined in one new point name.
For the following example point 1001 in photos 265 and 266 should obtain a new name.
Residuals of photo coordinates list limit = 4.0 * sigma Point Photo Vx' Vy' Rx'% Ry'% Wx' Wy' Nabla x' y' ( 1 / 1 0 0 0 ) ( 1 / 1 0 0 0 ) ------------------------------------------------------------------------------------------ **** 1001 265 4.4 -22.9 74 80 2.0 -10.2 -5.9 28.5 266 -1.7 -19.1 87 83 -0.7 -8.4 1.9 23.0 368 3.0 4.9 88 88 1.3 2.1 -3.4 -5.5 369 -3.8 7.1 80 88 -1.7 3.0 4.8 -8.1 370 1.3 -3.1 64 80 0.7 -1.4 471 -4.2 5.1 89 88 -1.8 2.2 4.7 -5.8 472 -3.6 -3.0 69 80 -1.7 -1.4 |
The reason for a data error in the adjustment can be a bad measurement or a wrong numeration of the points. Skipped photo measurements will be examined by BINGO concerning numeration errors. The right point name then appears in the list. Furthermore BINGO indicates points which had been skipped without a good reason. Such points appear again in the SKIP file in a UNSK statement.
Residuals of photo coordinates list limit = 4.0 * sigma Point Photo Vx' Vy' Rx'% Ry'% Wx' Wy' Nabla x' y' ( 1 / 1 0 0 0 ) ( 1 / 1 0 0 0 ) ------------------------------------------------------------------------------------------ * 9336 Cont.Pt. 265 4.4 -22.9 74 80 2.0 -10.2 -5.9 28.5 262 -2.9 2.4 64 70 -1.4 1.1 263 0.5 2.5 71 70 0.3 1.2 271 -4.9 -1.5 74 79 -2.3 -0.7 269 16290.2-28614.5 skipped ?? -2.2 2.9 if renamed to point 1006 270 0.2 -2.6 56 70 0.1 -1.2 268 -1.2 3.5 77 74 -0.5 1.6 267 1.4 -2.3 39 45 0.9 -1.4 9317 262 1.3 0.9 66 66 0.6 0.4 263 -0.1 -2.4 67 65 0.0 -1.2 : : : : : : : 270 -0.9 0.9 54 68 -0.5 0.5 269 3.6 -1.1 skipped but o.k. 268 1.8 -0.3 74 69 0.8 -0.1 |
In the example the point 1006 in photo 269 has erroneously received the name 9336. Here a manual correction is necessary. The renaming could also be performed by the program SKIP.