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Eija Honkavaara Eero Ahokas Juha Hyypp Juha Jaakkola Harri Kaartinen Risto Kuittinen Lauri Markelin Kimmo Nurminen 《ISPRS Journal of Photogrammetry and Remote Sensing》2006,60(6):387
Test field system calibration will be a fundamental part of the future photogrammetric production line. Accurate calibration and performance evaluations are necessary for fully assessing the stability and accuracy of digital sensing techniques. In this paper, a method of comprehensive geometric calibration in a test field has been developed and empirically tested using eight image blocks collected with three UltraCamD digital large format photogrammetric cameras. Permanent photogrammetric test fields form the basis of the method. Important components of the method are determination of system parameters, evaluation of systematic errors, and assessment of geometric accuracy. The results showed that UltraCamD images contained systematic deformations that could not be modeled with single lens additional parameter models. Good point determination accuracy was obtained despite the systematic errors; the typical accuracy was 2–3 μm in image space in the horizontal coordinates and 0.05–0.09‰ of the object distance in height. One of the cameras had significantly poorer performance. In the worst cases, the horizontal accuracy was 5 μm in image space and the height accuracy was 0.18‰ of the object distance. The analog cameras gave better results than the UltraCamD, but the development of appropriate mathematical models for UltraCamD as well as improvements in digital sensors may change the situation in the near future. 相似文献
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The aurora and other phenomena in near Earth space are becoming a considerable part of the science curriculum in upper secondary school (high school) in Norway. Introducing scientific methods to the young students is an important objective of the education, but experimental experience is mainly restricted to simple laboratory exercises under controlled conditions; observations of uncontrollable natural phenomena are generally left to academic scientists and researchers. The Space Physics Group and The Science Education and Outreach Group at The Department of Physics and Technology, University of Bergen, are constructing a Space Science Suitcase with a set of simple versions of instruments for monitoring solar and geophysical activity in near Earth space. The instruments will be lent to physics classes in upper secondary schools. 相似文献
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Information about the spatial variations of snow properties and of annual accumulation on ice sheets is important if we are to understand the results obtained from ice cores, satellite remote sensing data and changes in climate patterns. The layer structure and spatial variations of physical properties of surface snow in western Dronning Maud Land were analysed during the austral summers 1999/2000, 2000/01 and 2003/04 in five different snow zones. The measurements were performed in shallow (1–2 m) snow pits along a transect extending 350 km from the seaward edge of the ice shelf to the polar plateau. These pits covered at least the last annual accumulation and ranged in elevation from near sea level to 2500 m a.s.l. The Ø18 O values and accumulation rates had a good linear correlation with the distance from the coast. The mean accumulation on the ice shelf was 312±28 mm water equivalent (w.e.); in the coastal region it was 215±43 mm w.e. and on the polar plateau it was 92±25 mm w.e. The mean annual conductivity and grain size values decreased exponentially with increasing distance from the ice edge, by 48%/100 km and 18%/100 km respectively. The mean grain size varied between 1.5 and 1.8 mm. Depth hoar layers were a common phenomenon, especially under thin ice crusts, and were associated with low dielectric constant values. 相似文献
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Jouni I. Peltoniemi Jukka Piironen Jyri Nrnen Juha Suomalainen Risto Kuittinen Lauri Markelin Eija Honkavaara 《ISPRS Journal of Photogrammetry and Remote Sensing》2007,62(6):434-446
The Sjökulla test site is used for testing and calibrating aerial images. The permanent test field is made of four types of gravel (dark gabbro, grey granite, red granite, white limestone) in two sizes (diameters 8–16 mm and 4–8 mm) set in various patterns. The bidirectional reflection properties of the targets together with their temporal changes must be known in order to carry out radiometric and spectral evaluation and calibration.The bidirectional reflectance distribution functions (BRF) of the gravel have been measured several times in the test fields using portable field goniospectrometers belonging Finnish Geodetic Institute (FGI), and once using the European Goniometic Facility (EGO) of the Joint Research Centre (JRC) at Ispra, Italy. Detailed BRFs have been obtained, showing features typical to particulate media, e.g. a small bowl shape, strong backscattering, and smooth wavelength dependence. Temporal range measurements over several years show that the black gabbro and red granite are fairly stable, while the grey granite has changed somewhat over the years and the white limestone has experienced dramatic darkening effects, requiring action to be taken.The measured BRF data have increased the usability of the test field considerably. The results are also useful in the development and validation of scattering models for particulate media. The site has proved to be a good test bench for goniospectrometric instruments, too. 相似文献
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Lauri Markelin Eija Honkavaara Teemu Hakala Juha Suomalainen Jouni Peltoniemi 《ISPRS Journal of Photogrammetry and Remote Sensing》2010,65(4):409-421
Radiometric stability is a desired property of digital photogrammetric large-format sensors. This article presents a methodology for determining the radiometric stability of airborne imaging sensors in operational conditions in a test field and the results of stability evaluation of a large-format photogrammetric frame sensor DMC, from Intergraph. The imagery was collected in two days using nine different exposure settings, and images collected with variable exposure time and aperture were compared. The results showed promising stability in many cases, up to a level of 2% of the radiance, but less favorable results also appeared. Possible reasons for the unfavorable results could be the limitations of the experimental set-up or the instability of the sensor. DMC showed high radiometric performance potential, but high sensitivity to the exposure settings. Based on the results, recommendations for the future test field calibration and validation procedures were given. One limitation of the analysis was the insufficient information about the sensor stability potential; proposals were given to sensor manufacturers concerning the necessary information. 相似文献