{"id":60,"date":"2022-05-31T10:00:00","date_gmt":"2022-05-31T03:00:00","guid":{"rendered":"https:\/\/opengis.vn\/?p=60"},"modified":"2024-03-28T09:18:21","modified_gmt":"2024-03-28T02:18:21","slug":"gee-co-ban-3-loc-tap-anh-bang-metadata-va-ngay-thang","status":"publish","type":"post","link":"https:\/\/opengis.vn\/en\/blog\/gee-co-ban-3-loc-tap-anh-bang-metadata-va-ngay-thang\/","title":{"rendered":"[GEE c\u01a1 b\u1ea3n #3] L\u1ecdc t\u1eadp \u1ea3nh b\u1eb1ng metadata v\u00e0 ng\u00e0y th\u00e1ng trong Google Earth Engine"},"content":{"rendered":"

<\/h1>\n

Import t\u1eadp \u1ea3nh<\/h2>\n

\u0110\u1ea7u ti\u00ean, ch\u00fang ta s\u1ebd t\u00ecm v\u00e0 import t\u1eadp \u1ea3nh Sentinel-2 v\u00e0o.<\/p>\n

Ch\u00fang ta \u0111\u1ed5i t\u00ean t\u1eadp \u1ea3nh th\u00e0nh \u2018S2_collection\u2019.<\/p>\n

var S2_Collection = ee.ImageCollection(\"COPERNICUS\/S2_HARMONIZED\"),<\/code><\/pre>\n
Google Earth Engine cho ph\u00e9p ch\u00fang ta l\u1ecdc t\u1eadp \u1ea3nh theo 3 c\u00e1ch: l\u1ecdc theo v\u1ecb tr\u00ed, l\u1ecdc theo metadata v\u00e0 l\u1ecdc theo ng\u00e0y.<\/p>\n
L\u1ecdc theo v\u1ecb tr\u00ed<\/h2>\n
\u0110\u1ea7u ti\u00ean ch\u00fang ta s\u1ebd l\u1ecdc t\u1eadp \u1ea3nh theo v\u1ecb tr\u00ed. B\u1ea1n c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng c\u00e1c c\u00f4ng c\u1ee5 \u0111\u1ec3 v\u1ebd h\u00ecnh \u0111\u1ec3 l\u1ecdc nh\u01b0 post<\/a> tr\u01b0\u1edbc m\u00ecnh \u0111\u00e3 ch\u1ec9.<\/p>\n
Trong b\u00e0i n\u00e0y m\u00ecnh s\u1ebd ch\u1ecdn \u0111\u01a1n gi\u1ea3n m\u1ed9t \u0111i\u1ec3m \u0111\u1ec3 l\u1ecdc.<\/p>\n
\/\/Filter by location\nvar S2_filtered1 = S2_Collection.filterBounds(geometry);<\/code><\/pre>\n
Ch\u00fang ta s\u1ebd s\u1eed d\u1ee5ng h\u00e0m size() \u0111\u1ec3 ki\u1ec3m tra xem c\u00f3 bao nhi\u00eau \u1ea3nh ph\u00f9 h\u1ee3p v\u1edbi v\u1ecb tr\u00ed n\u00e0y \u2192 K\u1ebft qu\u1ea3 ra 447 \u1ea3nh.<\/p>\n
print ('filter by location', S2_filtered1.size());<\/code><\/pre>\n
L\u1ecdc theo metadata<\/h2>\n
Ti\u1ebfp theo ch\u00fang ta s\u1ebd l\u1ecdc theo metadata c\u1ee7a \u1ea3nh.<\/p>\n
Ch\u00fang ta c\u00f3 th\u1ec3 l\u1ecdc theo metadata c\u1ee7a \u1ea3nh nh\u01b0 gi\u00e1 tr\u1ecb PATH\/ROW, qu\u1ef9 \u0111\u1ea1o, ph\u1ea7n tr\u0103m che ph\u1ee7 b\u1edfi m\u00e2y,… b\u1eb1ng c\u00e1c b\u1ed9 l\u1ecdc nh\u01b0 ee.Filter.eq()<\/code>,ee.Filter.lt()<\/code>,…<\/p>\n
\u1ede \u0111\u00e2y m\u00ecnh s\u1ebd th\u1eed l\u1ecdc ra nh\u1eefng \u1ea3nh c\u00f3 ph\u1ea7n tr\u0103m pixel b\u1ecb m\u00e2y (CLOUDY_PIXEL_PERCENTAGE) d\u01b0\u1edbi 30.<\/p>\n
\/\/Filter by metadata\nvar S2_filtered2 = S2_filtered1.filter([ee.Filter.lt](http:\/\/ee.filter.lt\/)('CLOUDY_PIXEL_PERCENTAGE', 30));<\/code><\/pre>\n
M\u00ecnh ti\u1ebfp t\u1ee5c ch\u1ea1y l\u1ec7nh print \u0111\u1ec3 ki\u1ec3m tra k\u1ebft qu\u1ea3. \u1ede \u0111\u00e2y m\u00ecnh c\u00f2n 163 \u1ea3nh th\u1ecfa \u0111i\u1ec1u ki\u1ec7n.<\/p>\n
print('filter by metadata', S2_filtered2);<\/code><\/pre>\n
L\u1ecdc theo ng\u00e0y<\/h2>\n
Ti\u1ebfp theo, ch\u00fang ta c\u00f3 th\u1ec3 l\u1ecdc c\u00e1c \u1ea3nh trong m\u1ed9t ph\u1ea1m vi ng\u00e0y c\u1ee5 th\u1ec3 b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng c\u00e1c b\u1ed9 l\u1ecdc nh\u01b0 ee.Filter.date ()<\/code>.
\nB\u00e2y gi\u1edd ch\u00fang ta s\u1ebd l\u1ecdc c\u00e1c \u1ea3nh t\u1eeb ng\u00e0y 1\/1\/2019 \u0111\u1ebfn ng\u00e0y 1\/1\/2020:<\/p>\n
\/\/Filter by date\nvar S2_filtered3 = S2_filtered2.filter(ee.Filter.date('2019-01-01', '2020-01-01'));<\/code><\/pre>\n
\u0110\u1ec3 ki\u1ec3m tra k\u1ebft qu\u1ea3 sau khi \u00e1p d\u1ee5ng h\u1ebft c\u00e1c b\u1ed9 l\u1ecdc, m\u00ecnh ti\u1ebfp t\u1ee5c ch\u1ea1y l\u1ec7nh print. K\u1ebft qu\u1ea3 cu\u1ed1i c\u00f9ng ch\u00fang ta s\u1ebd ch\u1ec9 c\u00f2n 31 \u1ea3nh.<\/p>\n
print('Filter by date', S2_filtered3);<\/code><\/pre>\n
\"image\"<\/p>\n
R\u00fat ng\u1eafn code v\u00e0 hi\u1ec3n th\u1ecb k\u1ebft qu\u1ea3<\/h2>\n
Thay v\u00ec \u00e1p d\u1ee5ng l\u1ea7n l\u01b0\u1ee3t c\u00e1c b\u1ed9 l\u1ecdc, ch\u00fang ta c\u0169ng c\u00f3 th\u1ec3 ‘x\u00e2u chu\u1ed7i’ ch\u00fang l\u1ea1i nh\u01b0 sau:<\/p>\n
\/\/ Instead of applying filters one after the other, we can 'chain' them\nvar S2_filtered = S2_Collection.filter(ee.Filter.lt('CLOUDY_PIXEL_PERCENTAGE', 30))\n  .filter(ee.Filter.date('2019-01-01', '2020-01-01'))\n  .filter(ee.Filter.bounds(geometry));<\/code><\/pre>\n
M\u00ecnh comment out t\u1ea5t c\u1ea3 c\u00e1c d\u00f2ng code tr\u01b0\u1edbc \u0111\u00f3 b\u1eb1ng c\u00e1ch nh\u1ea5n Ctrl + \/<\/strong>, sau \u0111\u00f3 print k\u1ebft qu\u1ea3 ra \u0111\u1ec3 ki\u1ec3m tra xem c\u00f3 gi\u1ed1ng nh\u01b0 \u00e1p d\u1ee5ng t\u1eebng b\u1ed9 l\u1ecdc kh\u00f4ng nh\u00e9.<\/p>\n
print('S2_filtered', S2_filtered);<\/code><\/pre>\n
Nh\u01b0 c\u00e1c post<\/a> tr\u01b0\u1edbc, m\u00ecnh s\u1ebd d\u00f9ng h\u00e0m Map.addLayer<\/code> v\u00e0 Map.centerObject<\/code> \u0111\u1ec3 hi\u1ec3n th\u1ecb k\u1ebft qu\u1ea3 l\u00ean c\u1eeda s\u1ed5 b\u1ea3n \u0111\u1ed3.<\/p>\n
Map.centerObject(geometry, 9);\nMap.addLayer(S2_filtered, {min: 0.0, max: 3000, bands:'B4,B3,B2'}, 'Filtered Collection');<\/code><\/pre>\n
Video h\u01b0\u1edbng d\u1eabn l\u1ecdc t\u1eadp \u1ea3nh trong Google Earth Engine theo metadata v\u00e0 ng\u00e0y th\u00e1ng<\/h2>\n