A major advantage of satellite remote sensing is that the imagery acquired provides a synoptic view of the landscape. Thus, repeat coverage by the satellite on a regular basis permits the detection of changes in land‐cover over time. This study demonstrates the application of remote sensing technology to the monitoring of mining activities at the Athabasca Oil Sands region of Alberta, Canada. First, we describe the techniques used to match a time sequence of Landsat imagery, both spatially and spectrally, to ensure that the spectral changes through time are due to land‐cover variations. A series of spectral trajectories were then extracted to assess changes in land‐cover through time. Secondly, a land‐cover classification was produced from the baseline 1984 imagery and, using historic and future mine extents, the classification was analyzed to determine the proportion of each land‐cover type affected through development. Results of the analysis indicate that since 1984 there has been a larger reduction in mixedwood dense and broadleaf vegetation classes than mixedwood sparse or dense conifer stands in the area. Based on the delineations of mine‐site activity, the area of woodland and wetland habitat subject to development has increased from approximately 2,520 hectare (ha) in 1984 to 32,930 ha in 2005. 相似文献
Although the close association of word and image in medieval cartography is widely acknowledged, the significance of the relationship after the rediscovery of Ptolemy's Geography and throughout the Renaissance has been overlooked, despite Abraham Ortelius's choice of the term ‘Reader’ for users of the Theatrum orbis terrarum (1570). In this paper, the map of the world, which (as in Ptolemy's Geography) opens Ortelius's Theatrum, is analysed to show how Ortelius's concept of space was very different from Ptolemy's. Attention is drawn to the content of the texts on the map, to Ortelius's notion of geography as the eye of history, and to the importance in the Renaissance of the emblem as a conceit, or device, in the system of acquisition and transmission of knowledge. As in emblems, the words on Ortelius's map are not there to explain or to comment on what is seen but to give the image meaning; the purpose of the map is to invite contemplation of God's world. The map is contradictory, however; for Ortelius's accurate and up‐to‐date presentation of the physical world is qualified by a verbal statement that the world is ‘nothing’, a mere pinpoint in the immensity of the universe. It is concluded that Ortelius was not a geographer in the same way Ptolemy was, and that Ortelius was using geography as a philosopher and his world map as an illustration of his moral and religious thinking. 相似文献
Timber structures can be degraded during their life both by structural problems and by biological degradation factors like fungi and insects. The occurrence of those biodegradation agents could lead to a loss of their structural integrity, in the absence of appropriate maintenance. An early assessment of the decay is even more important when the wooden structures are part of historical buildings, in the interest of conservation of cultural heritage.
This article presents an application of microwave reflectometry for the in situ evaluation of timber structures. The measurement system allows detecting anomalies inside the material in a non-destructive and non-invasive manner.
The reflection coefficient is measured by means of a vector network analyzer (VNA) using a double-ridge antenna which transmits the continuous-wave (CW) microwave signal and receives the signal reflected by the material under investigation.
Measurements on laboratory models demonstrated the feasibility of the method. Results obtained on timber beam sections, compared with the findings of traditional investigation methodologies, demonstrate the potentiality of microwave reflectometry, suggesting its possible usefulness during the diagnostic phase as a non-invasive tool for preliminary screening. 相似文献