Story maps
故事地圖
View from the sky 從天而看
©2009 SpatioEpi.com
Data source: NASA's LandSat 7 Thematic Mapper dated November 2005
Satellite image provides a valuable tool for understanding the land use/land cover pattern over a large area. This image provides a snapshot of the Pearl River Delta in South China, with Hong Kong being shown in the lower right corner. In this satellite image, taken in November 2005, red indicates vegetation cover, grey indicates built-up area, dark blue indicates water and light blue indicates sediment-laden water.
人造衛星圖片是一個分析土地利用和土地覆蓋的好工具。本衛星圖片拍攝於2005年11月，圖示南中國珠江三角洲情況，右下方為香港。在近紅外線的光譜下，植被會呈現紅色，已發展的土地會呈現灰色，清澈的水體會呈現深藍色，而載有沈積物的水體則呈現淺藍色。
Related Article
Satellite image 人造衛星圖片
Satellite image, one of the products from remote sensing techniques, reflects light radiance of any object at numerous ranges of electromagnetic spectrum. Among the ranges, the near infrared region is commonly used to assess the change of vegetation cover and water quality.
In these maps, the brightness of the red colour is mainly determined by the species and healthiness of vegetation. Bright red normally represents dense coverage of woodland in mountain areas while light red represents cultivated land (e.g. lowland of the Pearl River Delta estuary)
As clear water gives almost no reflection in the near infrared spectrum, it often appears to be dark in colour. However, when water is filled with suspended sediment or pollutant, this will allow better reflectivity and result in a brighter appearance.
人造衛星圖片是遙感技術下其中一個產物，它主要是用作反映物件在不同電磁光譜範圍的光線放射情況。 在不同的電磁光譜範圍中，近紅外線通常是用作分析植被分佈及檢測水體素質。
在近紅外線中, 紅色的光亮度主要受植被的品種和健康情況影響。 以網頁上的珠江三角洲衛星圖為例，深紅色的地方為山上的林地，而淺紅色的地方則是耕地 (例如三角洲河口部份) 。
清澈的水體在紅外線下基本上是不會反射任何光線，故它們通常呈現深藍色或黑色。不過，如果水體中運載沈積物或污染物，它們會增加水體的反射能力，從而令水體呈現不同程度的淺藍色。
Related maps 相關地圖
Other resources 其他資訊
Organisations 有關機構
- Introduction to Remote Sensing, NASA
Further information 詳細資料
- 香港中文大學太空與地球信息科學研究所 Institute of Space and Earth Information Science, The Chinese University of Hong Kong ISEIS