Uncomment the following line to install geemap if needed.

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# !pip install geemap

# !pip install geemap

How to find out the greenest day of the year¶

Import libraries¶

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import ee
import geemap

import ee import geemap

Create an interactive map¶

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Map = geemap.Map()
Map

Map = geemap.Map() Map

Define a region of interest (ROI)¶

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countries = ee.FeatureCollection("users/giswqs/public/countries")
Map.addLayer(countries, {}, "countries")

countries = ee.FeatureCollection("users/giswqs/public/countries") Map.addLayer(countries, {}, "countries")

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roi = countries.filter(ee.Filter.eq("id", "USA"))
Map.addLayer(roi, {}, "roi")

roi = countries.filter(ee.Filter.eq("id", "USA")) Map.addLayer(roi, {}, "roi")

Filter ImageCollection¶

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start_date = "2019-01-01"
end_date = "2019-12-31"

l8 = (
    ee.ImageCollection("LANDSAT/LC08/C01/T1_TOA")
    .filterBounds(roi)
    .filterDate(start_date, end_date)
)

start_date = "2019-01-01" end_date = "2019-12-31" l8 = ( ee.ImageCollection("LANDSAT/LC08/C01/T1_TOA") .filterBounds(roi) .filterDate(start_date, end_date) )

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# print(l8.size().getInfo())

# print(l8.size().getInfo())

Create a median composite¶

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median = l8.median()

visParams = {
    "bands": ["B4", "B3", "B2"],
    "min": 0,
    "max": 0.4,
}

Map.addLayer(median, visParams, "Median")

median = l8.median() visParams = { "bands": ["B4", "B3", "B2"], "min": 0, "max": 0.4, } Map.addLayer(median, visParams, "Median")

Define functions to add time bands¶

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def addNDVI(image):
    ndvi = image.normalizedDifference(["B5", "B4"]).rename("NDVI")
    return image.addBands(ndvi)

def addNDVI(image): ndvi = image.normalizedDifference(["B5", "B4"]).rename("NDVI") return image.addBands(ndvi)

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def addDate(image):
    img_date = ee.Date(image.date())
    img_date = ee.Number.parse(img_date.format("YYYYMMdd"))
    return image.addBands(ee.Image(img_date).rename("date").toInt())

def addDate(image): img_date = ee.Date(image.date()) img_date = ee.Number.parse(img_date.format("YYYYMMdd")) return image.addBands(ee.Image(img_date).rename("date").toInt())

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def addMonth(image):
    img_date = ee.Date(image.date())
    img_doy = ee.Number.parse(img_date.format("M"))
    return image.addBands(ee.Image(img_doy).rename("month").toInt())

def addMonth(image): img_date = ee.Date(image.date()) img_doy = ee.Number.parse(img_date.format("M")) return image.addBands(ee.Image(img_doy).rename("month").toInt())

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def addDOY(image):
    img_date = ee.Date(image.date())
    img_doy = ee.Number.parse(img_date.format("D"))
    return image.addBands(ee.Image(img_doy).rename("doy").toInt())

def addDOY(image): img_date = ee.Date(image.date()) img_doy = ee.Number.parse(img_date.format("D")) return image.addBands(ee.Image(img_doy).rename("doy").toInt())

Map over an ImageCollection¶

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withNDVI = l8.map(addNDVI).map(addDate).map(addMonth).map(addDOY)

withNDVI = l8.map(addNDVI).map(addDate).map(addMonth).map(addDOY)

Create a quality mosaic¶

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greenest = withNDVI.qualityMosaic("NDVI")

greenest = withNDVI.qualityMosaic("NDVI")

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greenest.bandNames().getInfo()

greenest.bandNames().getInfo()

Display the max value band¶

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ndvi = greenest.select("NDVI")
palette = [
    "#d73027",
    "#f46d43",
    "#fdae61",
    "#fee08b",
    "#d9ef8b",
    "#a6d96a",
    "#66bd63",
    "#1a9850",
]
Map.addLayer(ndvi, {"palette": palette}, "NDVI")

ndvi = greenest.select("NDVI") palette = [ "#d73027", "#f46d43", "#fdae61", "#fee08b", "#d9ef8b", "#a6d96a", "#66bd63", "#1a9850", ] Map.addLayer(ndvi, {"palette": palette}, "NDVI")

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Map.addLayer(greenest, visParams, "Greenest pixel")
Map

Map.addLayer(greenest, visParams, "Greenest pixel") Map

Display time bands¶

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Map.addLayer(
    greenest.select("month"),
    {"palette": ["red", "blue"], "min": 1, "max": 12},
    "Greenest month",
)

Map.addLayer( greenest.select("month"), {"palette": ["red", "blue"], "min": 1, "max": 12}, "Greenest month", )

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Map.addLayer(
    greenest.select("doy"),
    {"palette": ["brown", "green"], "min": 1, "max": 365},
    "Greenest doy",
)

Map.addLayer( greenest.select("doy"), {"palette": ["brown", "green"], "min": 1, "max": 365}, "Greenest doy", )