Calculating dates of unique images for a certain area in imageCollection using Google Earth Engine

Question

I am trying to retrieve an image from the Sentinel-1 image collection where the user provides a time of interest and a region of interest. Since Sentinel-1 provides new images for a region only every 7 days, I want to calculate these unique dates so I could constraint the user to only pick these as a toi. What I have so far is this code:

def get_available_dates_from_collection(collection):
    dates = collection.map(lambda image:
                           ee.Feature(None, {'date': image.date().format('YYYY-MM-dd')}))\
                                                     .distinct('date').aggregate_array('date')
    return dates.getInfo()

The function calculates all the available dates in an image collection and I use the list returned to constraint the user to pick a date within that list. Since the roi isn't considered here, 6 dates out of 7 will return the same image.

Is there a way that I could calculate the unique dates for each unique image of that region?

Answer 1

You can just filter your collection by your roi beforehand using collection.filterBounds(roi) (or roi.geometry(), depends on your roi).