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48 lines
1.2 KiB
Python
48 lines
1.2 KiB
Python
"""Map an expression.
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Computes the mean NDVI and SAVI by mapping an expression over a collection
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and taking the mean. This intentionally exercises both variants of
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Image.expression.
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"""
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import datetime
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import ee
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import ee.mapclient
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ee.Initialize()
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# Filter the L7 collection to a single month.
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collection = ee.ImageCollection('LANDSAT/LE07/C02/T1_TOA').filterDate(
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datetime.datetime(2002, 11, 1), datetime.datetime(2002, 12, 1)
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)
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def NDVI(image):
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"""A function to compute NDVI."""
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return image.expression('float(b("B4") - b("B3")) / (b("B4") + b("B3"))')
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def SAVI(image):
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"""A function to compute Soil Adjusted Vegetation Index."""
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return ee.Image(0).expression(
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'(1 + L) * float(nir - red)/ (nir + red + L)',
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{
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'nir': image.select('B4'),
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'red': image.select('B3'),
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'L': 0.2
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})
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vis = {
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'min': 0,
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'max': 1,
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'palette': [
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'FFFFFF', 'CE7E45', 'DF923D', 'F1B555', 'FCD163',
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'99B718', '74A901', '66A000', '529400', '3E8601',
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'207401', '056201', '004C00', '023B01', '012E01',
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'011D01', '011301'
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]}
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ee.mapclient.centerMap(-93.7848, 30.3252, 11)
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ee.mapclient.addToMap(collection.map(NDVI).mean(), vis)
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ee.mapclient.addToMap(collection.map(SAVI).mean(), vis)
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