Hi,
To reiterate your explanation - ‘SIMPLE’ will return a mosaic of all least cloud cover acquisitions in the months I specified
Yes, but depends if you specify the leasCC
mosaicking order option in the request, by default this is mostRecent
.
However, the ORBIT and TILE will do that same, but based on number of TILES/ORBITS available per month, whereas, “SIMPLE” will only care about the order and not if it is TILE/ORBIT?.
Perhaps I wasn’t so clear, so let me try again. Let’s say you make a request for a time interval 2022-02-05
to 2022-06-20
. In this time interval there is a number of observations for the specific area you’re making the request.
-
If mosaicking is TILE
, then your samples
object will loop through all of these available observations for the requested time interval. The order of these observations is defined by the parameter mosaickingOrder
, meaning it can be mostRecent
/leastRecent
/leastCC
(check docs for more info). If you want to obtain an image with such a request, you have to specify which sample you want to return (e.g. the first, the middle, the last, the one with max NDVI, the one with lowest B03, etc. - usually done with a for-loop returning the specific value (see evalscript example above for this)
-
If mosaicking is ORBIT
, it’s very similar as with TILE
, but in principle there will be fewer samples in the samples
array, because the observations from the same orbit are already merged together.
-
If mosaicking is SIMPLE
, then the mosaicking is already done for you, but in a simplistic way, you will already get a single sample/image, which is stacked accordingly to the mosaicking order you provide
Well, can you explain what is the process behind this approach. It returns a mosaic of all least cloud cover acquisition that fall within 17 percent or below (The CC percentage in question)?
So, if you say leastCC
, the image will show the observation coming from the tile with the least cloud coverage (on the S2 tile level). If this tile has a part which was not covered by the satellite, the next least cloudy observation will fill those gaps, and so on. There are no thresholds here, just the order. If you want to limit observations from S2 tiles to a certain cloud coverage value, then I suggest you use the maxcc
parameter in the request, which will just ignore all observations coming from such tiles and ignore them also in the mosaicking more info here.
But let’s take a step back. You say the following:
I am trying to obtain one cloud free image from an FOI for every last week in a month.
I suggest you create a separate request for each of the time intervals (one week time interval before end of month) using the SIMPLE
mosaicking and the leastCC
mosaicking order. Provided there are any cloud-free observations, this will return that observation.
However, a warning - one week long time interval is relatively short, it’s possible that you won’t get any observations this way if you’re unlucky.