Hi, I have been playing around with SNAP and a few of the sample datasets over the weekend but I keep receiving a DataBuffer OperatorException message, which I have now learnt could be due to only having 4GB of RAM.
Is there an archive of imagery stored somewhere that I can view?
I am particularly interested in images captured over the UK last month, in the hopes of narrowing a search for a sunken fishing boat, on a relatively short journey, approximately 1 mile offshore.
Any help would be very much appreciated. Thank you.
You can try to have a look at sentinel-hub (part of the Euro Data Cube service). Their EO-Browser and/or Sentinel Playground should be interesting for you.
You will need to download the data to your environment or use an associated cloud environment in case you want to process it with SNAP.
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Hi Cristiano, thanks for the reply.
I follow a company on twitter called TankerTrackers who also suggested Sentinel-Hub, and took a brief look at the Sentinel Playground, but as I was just starting to look into satellite imagery thought that it wasnât what I was looking for, as the available imagery I viewed seem to have different overlays which made it hard to distinguish features on the ground / at sea. Have I been too hasty?
I viewed the location of interest on Zoom Earth which gave a very clear image of the features, both on the ground and on the water, but this data is obviously 2+ years old.
Also, on the day of interest (27/01/21) there was unfortunately thick cloud cover. My research discovered that satellites with SAR Imagery are able to retrieve images regardless of weather conditions, and at night, which is also important, and a capability mentioned on the ICEYE website which I was very excited and hopeful about.
I was particularly interested in the Dark Vessel Detection Dataset available on ICEYE, but believe this tracks vessels via their AIS numbers. Unfortunately the missing fishing vessel of interest did not have an AIS number transmitting, as it was only 10 x 5 meters approx. and working in local waters. So I think in order to track this vessel I will need to locate it at the start of its journey at 10am, and track either it or the white wake left behind (as this is more visible from space), until the event later that night between 10pm - midnight.
If I can achieve this it will move the search forward significantly.
With all this in mind, do you still think Sentinel-hub, EO-browser, and sentinel playground are worth reinvestigating?
Thanks for all your help Cristiano.
Hi Robert, I knowledgeable are you with Satellite Remote Sensing in general? From your last reply I get the feeling that you donât fully grasp the concepts and state of the art at hand.
There are several important concepts when thinking about Satellite data (images) acquisition:
- resolution
- swath width
- revisit time
- cloud coverage
You probably should have a look at Newcomers Earth Observation Guide or Remote Sensing Tutorials.
That 10x5 meter vessel is probably too small to show up in any of free/open data acquisitions (optical or radar) and the commercial data is usually tasked upfront (i.e. we ask and pay for a number of acquisitions over an area). It would require quite some luck to have had IceEye sensing your area of interest in that same day and time (in spotlight mode they have 1x1m resolution for 5x5km swath, stripmap mode, 3x3 m resolution for 30x50km swath), or even TerraSAR-X (more or less the same characteristics as IceEye).
I did a quick check on TerraSAR-X Archive and thereâs werenât that many acquisitions made over for example for the Iberian Peninsula general area (using this a sample reference) - only one acquisition over a few major cities during that whole day.
EO-Browser and Sentinel-Playground only give you free access to free and open data - you may enquiry with sentinel-hub (Sinergise) to see if they can give you access to commercial data and at what conditions.
Hi Cristiano, thatâs very informative, thank you.
You will have to give me some time to check out the Newcomers Guide and Remote sensing tutorials, as they are quite comprehensive and will take time for me to get a grasp of these concepts. But yes you are right, I am very new, about 2 weeks into learning about satellite imagery, but glanced over the newcomers guide with interest.
I somewhat naively took too much information from the ICEYE Orbits page, seeing the .gif image of the earth and orbiting satellite trajectories I took this to be âfactâ 
The location of interest is Llandudno, just off the North Wales coast, UK, and from that image it looked as though the satellite passed directly over the Irish sea, which is almost a direct path above the location of interest.
This, together with the fact the Orbits page says 15 orbits per day, which by my calculation would be a pass over every 1hr 36 minutes over a 24hr period, and also the use of SAR to penetrate cloud cover, made me prematurely confident that I was potentially close to locating the lost vessel.
Based on what you have said above re swath I am guessing the stripmap mode is more likely to meet my requirements, as the total area of interest is 20x2km max. There is a specific location on the route that has a higher probability of being the location of the vessel, which a 2x2km swath should cover, and so may benefit from spotlight mode. Apologies if I am using the terminology in the wrong places here, I am still to read up in more detail.
I have just taken a look at TerraSAR-X Archive, but in the âavailable scenes in the area of interestâ the available scenes only date back to 2019. Is it possible to request more up to date scenes via the request box? And I will look into commercial access, if possible, after familiarising myself a bit more with the key concepts.
Thanks for all your help Cristiano.