how to calculate ndvi
TRANSCRIPT
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NDVIを計算する東京大学大学院新領域創成科学研究科
中村英史
この作品はCC BY 4.0 ライセンス の下に提供されています。
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このスライドは
「Landsat 8 画像でNDVI 算出」 小池 隆(合同会社緑IT事務所),中村 和彦・福本 塁(NPO法人オープンコンシェルジュ),岩田敏彰(独立行政法人産業技術総合研究所) (http://www.slideshare.net/openconcierge/landsat-8ndvi)
を元に作成されています.
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手順
1. Landsat 8 画像のダウンロード
2. 画像の読み込み
3. NDVIを計算
4. 計算結果を表現
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NDVIとは• 正規化差分植生指数(Normalized Difference Vegetation Index; NDVI)
• 植生の量や活性を示す値
• NDVI=(NIR-Red)/(NIR+Red)
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[NIR:近赤外, Red:赤色光]
参照: とらりもんHOME (http://pen.agbi.tsukuba.ac.jp/~RStiger/hiki2/)
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1. Landsat 8 画像のダウンロード
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産総研のLandBrowser(http://landbrowser.geogrid.org/landbrowser/)を開きます
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検索したい場所を入力 (今回は例として東京大学秩父演習林)
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Cloudの値を10以下に変更する
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期間も変更できる
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雲が晴れたら「Save」をクリック
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「Save」をクリック
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「Band4」「Band5」をそれぞれダウンロード
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「Band4」は赤色光,「Band5」は近赤外光のバンドです今回はこれらの画像データを用います
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2. 画像の読み込み
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QGISを起動した後…
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「ラスタレイヤの追加」をクリック
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ダウンロード画像(tiff)を読み込む
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3. NDVIを計算
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QGISの「ラスタ計算機」を用います
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出力レイヤを忘れずに指定
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NDVI=(NIR - Red) / (NIR + Red)なので
NDVI=(Band5 -Band4) / (Band5 + Band4)となります
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式を入力ダブルクリックで式の欄に入力される
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4. 計算結果を表現
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レイヤを右クリック,「プロパティ」を選択
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「スタイル」を選択
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「単バンド擬似カラー」を選択
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「Greens」を選択
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「分類」をクリック
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NDVIが高いほど緑色が濃くなるように表現できます
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ありがとうございました.
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