Dear all,
I am new with both Sentinel data and this forum. So, apologies for a trivial question.
I want to process Sentinel1A data and I know that this is 12-day temporal resolution (revisiting). However, when I checked my experiment area, I found that no data (i.e., a pair of consecutive images) has 12-day interval. They are at least 24 days in separation and even longer.
Can anyone describe me what caused this? It is in urban area.
thanks,
Luyen.
It depends where your area of interest is and when the data is acquired. Have a look at the observation scenarios https://earth.esa.int/web/sentinel/missions/sentinel-1/observation-scenario
For Europe, there should be 6 day revisits with S1A and S1B. For other parts of the world it can be less depending on where it is.
Hi Luis,
Thanks for your advice. I had a look on Sentinel-1 Constellation Observation Scenario map. I am searching data in Hanoi area of Vietnam over a 4 year period, from 2014 until now. It is certainly not in Europe, so I believe that it should be 12-day revisits area. However, there is not any pair with 12-day separation. When searching on another area, that is about 200 km far away from Hanoi, most of available images are in 12-day interval.
Cheers,
Luyen.
according to the Google Earth Engine, there are around 350 images which (at least partially) cover the Hanoi area.
Where did you search for the data? Do you need SLC or GRD?
Hi ABraun,
I searched data from: https://scihub.copernicus.eu/dhus/#/home
I refined by S1A_*, SLC, IW, and relative orbit number: 128
I focus only on images that cover the same area.
Cheers,
Luyen
Hi, Just to add that the S1 planning (https://sentinel.esa.int/web/sentinel/missions/sentinel-1/observation-scenario/acquisition-segments) indicates the following acquisitions over Hanoi during August for relative orbit 128:
S1-A 06/08/2018
S1-A 18/08/2018
S1-B 24/08/2018
S1-A 30/08/2018
So just for S1-A there are acquisitions every 12 days while including S1-B this is reduced to 6 days for part of the month. I notice that Hanoi is also imaged for relative orbit 91 (descending pass) on:
S1-A 03/08/2018
S1-A 15/08/2018
S1-B 21/08/2018
S1-A 27/08/2018
Hi @peter.meadows,
Yes, you are correct but for the time from March 2017 only. Before that time, the time spans are longer than 12 days and even more than one month in some period.
Cheers,
Luyen.
That’s the case for many places. For me, I only have regular acquisition from July 2017.
You can find your observation scenarios for your dates in the archive : https://sentinel.esa.int/web/sentinel/missions/sentinel-1/observation-scenario/archive
Here’s an example where you can see that a lot of places did not have a 12-days revisit time (especially in Antarctica)
Hi
I am working with Sentinel -1 data for Tolima region in Colombia ( 75 °00 w , 3°55’ n). I found that there are 2 months of gap information in 2018. the atached figure was created in google earth engine, but I also checked the available information in copernicus repository, finding the same.
So, I would like to know which could be the reason for this lack of data.
Many thanks,
Andrés
