Uncomment the following line to install geemap if needed.

In [ ]:

# !pip install geemap

# !pip install geemap

How to find out the greenest day of the year¶

Import libraries¶

In [ ]:

import ee
import geemap

import ee import geemap

Create an interactive map¶

In [ ]:

Map = geemap.Map()
Map

Map = geemap.Map() Map

Define a region of interest (ROI)¶

In [ ]:

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

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

In [ ]:

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¶

In [ ]:

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) )

In [ ]:

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

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

Create a median composite¶

In [ ]:

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¶

In [ ]:

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)

In [ ]:

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())

In [ ]:

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())

In [ ]:

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¶

In [ ]:

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

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

Create a quality mosaic¶

In [ ]:

greenest = withNDVI.qualityMosaic('NDVI')

greenest = withNDVI.qualityMosaic('NDVI')

In [ ]:

greenest.bandNames().getInfo()

greenest.bandNames().getInfo()

Display the max value band¶

In [ ]:

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')

In [ ]:

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

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

Display time bands¶

In [ ]:

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', )

In [ ]:

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', )

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Last update: 2023-03-19
Created: 2020-07-01