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Precyzja i niezawodność pomiaru środków rzutów w rzeczywistych aerotriangulacjach

Ziobro J.

Prace Instytutu Geodezji i Kartografii

2007

T. 53, z. 111

90-99

Przedstawiono wyniki badań precyzji i niezawodności pomiaru środków rzutów uzyskanych w produkcyjnych aerotriangulacjach wykonanych w kraju w ciągu ostatnich kilku lat dla skal zdjęć lotniczych 1:13 000, 1:19000 i 1:26000. Badaniami objęto 25 bloków o łącznej liczbie 30 tys. zdjęć. Badania oparto na ponownym wyrównaniu danych produkcyjnych przy restrykcyjnym przestrzeganiu warunków poprawnego wyrównania. Wyrównania poprzedziło przed wyrównawcze wykrywanie błędów grubych i złego podziału pomiarów na profile GPS metodą opracowaną przez autora artykułu. Analizę występowania błędów grubych w obserwacjach i ocenę niezawodności pomiaru przeprowadzono metodą data snooping W. Baarda. Przeciętna precyzja pomiaru współrzędnej środka rzutów dla 25 bloków wyniosła 10.7 cm. Niezawodność pomiaru w sieci okazała się wystarczająca w aerotriangulacjach dla skali zdjęć 1: 13 000. W aerotriangulacjach dla obu mniejszych skal niezawodność pomiaru była niezadowalająca.

Correctness of network adjustment depends on selection of proper functional and statistical model and on eliminating mistakes and gross errors. Fulfilment of these conditions for aerial triangulation can be troublesome, as it involves even four groups of observations, different in character and origin. These groups are sometimes characterised by different precision of measurement, having often only roughly determined mean errors and variable levels of reliability of network observations. It makes more difficult correct weighting of observations and detection of gross errors. Above described problem is particularly related to measurement of projection centers, as observers often report mean error roughly or did not give it at alI. The aim of this study was to determine precision of measurement of projection centers obtained in real blocks. The second goal of the work was to estimate reliability of this group of measurements in aerial triangulations for three scales of aerial photographs. The study was based on renewed data preparation from production blocks, strictly obeying conditions of correctness of adjustment. Adjustment was preceded by pre-adjustment detection of gross errors and bad assignment of measurements into GPS profiles, using method prepared by the author. Production results were derived from various measurement systems and adjustment softwares; they were characterised by numerous imperfections concerning functional and statistical model, which were generally caused by the applied technologies. 25 blocks were selected for testing, applying three scales of aerial photographs: 1:13 000, 1:19 000 and 1:26 000, most frequently used in our country. Appearance of measurement of projection centers (on the average for 90 % of photographs in the block) was the second, important feature of these blocks. Number of photographs in blocks varied from 136 to 3402, and total number of photographs in all blocks was about 30 000. Verified mean errors a priori, obtained from 25 adjustments, reach on the average 10.7 cm and standard deviation is 4.1 cm. Analysis of global internal reliability of measurement of projection centers for particular scales revealed, that in blocks of photographs at a scale of 1 : 13 000 average redundancy component reached 0.50 for X, 0.48 for Y and 0.75 for Z. So, it can be concluded, that reliability of measurement of projections centers in these aerial triangulations was sufficient. For these blocks mean residual for all three coordinates of projection center reached 76 % of the average mean error a priori. For scales 1: 19 000 and 1:26 000, in 9 out of 15 blocks redundancy component of horizontal coordinates of projection centers was lower than 0.25. Sufficient level of reliability was obtained only for one block. Average residual of horizontal coordinates was only ca. 56 % of mean error a priori.