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Suzuki, M. (1985) Evapotranspiration Estimates of Forested Watersheds in Japan Using the Short-time Period Water-budget Methods. Journal of Japanese Forest Society, 67: 115-125. (in Japanese with English summary)


短期水収支法による森林流域からの蒸発散量推定
Evapotranspiration estimates of forested watersheds in Japan using the short-time period water-budget method  [in Japanese]   
鈴木 雅一 (SUZUKI Masakazu)         
京都大学農学部 (Fac.of Agr., Kyoto Univ.)

長期間にわたって水収支観測がなされている日本各地の森 林流域の記録をもとに, 短期水収支法を用いて流域の蒸発散量とその季節変化を求めた。検討には桐生, 川向, 竜の口山, 釜淵, 去川の5試験地, 9流域のそれぞれ10年から40年間の日雨量, 日流出量記録が用いられた。短期水収支法では, 渇水による蒸発散低下は水収支期間内の最小流量に対応して生じ, 蒸発散低下をもたらす限界流量が流域ごとに定められた。渇水による蒸発低下の例を除外して求めた蒸発散量季節変化は, 植生が著しく変わらないとき集計期間が異なってもほぼ同様の結果となった。森林の伐採や山火事によって蒸発散量が減少する傾向は各流域とも同様であるが, その変化が通年にわたり生じた流域とおもに夏期に生じた流域があった。求められた蒸発散量とその季節変化は各流域の気象, 植生を反映する値として, 森林流域の蒸発散量推定式作成の基礎資料になるといえる。

The annual and monthly evapotranspiration were estimated using the method of the short-time period water-budget on 9 water-sheds located in 5 experimental areas in Japan. Daily precipitation and discharge records and a period of 10 to 40 years for each watershed were used in this estimation. The appearance of an evapotranspiration decline because of drought has a relationship with the minimum discharge-rate in a water-budget period. The critical discharge-rate for an evapotranspiration decline can be determined for each watershed. On a watershed without a remarkable change of vegetation, seasonal variations of different averaging periods of years for evapotranspiration under no drought conditions change in the same way. Evapotranspiration decreases after clear-cuttings and forest fires on every watershed where such events have occurred, but the tendency for changes in seasonal variations vary with each watershed.


posted by maetel
OpenCV: cvFindContours( )

cvFindContours()
int cvFindContours(CvArr* image, CvMemStorage* storage, CvSeq** first_contour, int header_size=sizeof(CvContour), int mode=CV_RETR_LIST, int method=CV_CHAIN_APPROX_SIMPLE, CvPoint offset=cvPoint(0, 0))

Finds the contours in a binary image.

Parameters:
  • image – The source, an 8-bit single channel image. Non-zero pixels are treated as 1’s, zero pixels remain 0’s - the image is treated as binary . To get such a binary image from grayscale, one may use Threshold , AdaptiveThreshold or Canny . The function modifies the source image’s content
  • storage – Container of the retrieved contours
  • first_contour – Output parameter, will contain the pointer to the first outer contour
  • header_size – Size of the sequence header, \ge \texttt{sizeof(CvChain)} if \texttt{method} =\texttt{CV\_CHAIN\_CODE} , and \ge \texttt{sizeof(CvContour)} otherwise
  • mode

    Retrieval mode

    • CV_RETR_EXTERNAL retrives only the extreme outer contours
    • CV_RETR_LIST retrieves all of the contours and puts them in the list
    • CV_RETR_CCOMP retrieves all of the contours and organizes them into a two-level hierarchy: on the top level are the external boundaries of the components, on the second level are the boundaries of the holes
    • CV_RETR_TREE retrieves all of the contours and reconstructs the full hierarchy of nested contours
  • method

    Approximation method (for all the modes, except CV_LINK_RUNS , which uses built-in approximation)

    • CV_CHAIN_CODE outputs contours in the Freeman chain code. All other methods output polygons (sequences of vertices)
    • CV_CHAIN_APPROX_NONE translates all of the points from the chain code into points
    • CV_CHAIN_APPROX_SIMPLE compresses horizontal, vertical, and diagonal segments and leaves only their end points
    • CV_CHAIN_APPROX_TC89_L1,CV_CHAIN_APPROX_TC89_KCOS applies one of the flavors of the Teh-Chin chain approximation algorithm.
    • CV_LINK_RUNS uses a completely different contour retrieval algorithm by linking horizontal segments of 1’s. Only the CV_RETR_LIST retrieval mode can be used with this method.
  • offset – Offset, by which every contour point is shifted. This is useful if the contours are extracted from the image ROI and then they should be analyzed in the whole image context



Learning OpenCV: Chater 8. Contours: Contour Finding
: 234p
"the concept of a contour tree"


Suzuki, M. (1985) Evapotranspiration Estimates of Forested Watersheds in Japan Using the Short-time Period Water-budget Methods. Journal of Japanese Forest Society, 67: 115-125. (in Japanese with English summary)


posted by maetel