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This question is based on a previous post: Filter two image collections by the same aqusition date in Google Earth Engine

I would like to expand the question to try to filter collections to get images that are within one day of each other (i.e., image from collection 1 is within +/- one day of image from collection 2).

I have written the following code in geemap (based on previous question) to get coincident image dates, given two image collections:

col1 = ee.ImageCollection('LANDSAT/LE07/C02/T1_L2') \
    .filter(ee.Filter.calendarRange(1998, 2013,'year')) \
    .filterBounds(pts)

col2 = ee.ImageCollection('LANDSAT/LT05/C02/T1_L2') \
    .filter(ee.Filter.calendarRange(1998, 2012,'year')) \
    .filterBounds(pts)

def datefunc(image):
    date = ee.Date(image.get('system:time_start')).format("YYYY-MM-dd")
    date = ee.Date(date)
    return image.set('date', date)

col1_date = col1.map(datefunc)
col2_date = col2.map(datefunc)

filterTimeEq = ee.Filter.equals(
    leftField='date',
    rightField='date'
)

simpleJoin = ee.Join.simple()

col_new = ee.ImageCollection(simpleJoin.apply(col1_date, col2_date, filterTimeEq))

Is there any way I can modify the above code to get near coincident imagery?

1 Answer 1

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Solved! I got it working using ee.Filter.maxDifference. I used the original 'system:time_start' values (which are in milliseconds) and set the max difference as one day. The full code looks like this:

filterNear = ee.Filter.maxDifference(
    difference = 86400000,
    leftField='system:time_start',
    rightField='system:time_start'
)

col_near = ee.ImageCollection(simpleJoin.apply(col1, col2, filterNear))

Where 86400000 is the number of milliseconds in 24 hours.

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