Displaced color channels and some misc info

Hello,

we have found images, which have displaced color images (it looks like that channels have been acquired at slightly different times). The phenomenon is not visible for the most of the image, but in our task - finding commercial aircraft on satellite images, the artefacts are highly visible, as in the image below:

The image in question is 20190921_025440_53_105c_3B_AnalyticMS_SR.tif

The crop-out of the image is from the right side of the image, almost at the edge. I can get you speed of the aircraft if you need it to estimate the delay between the channels... but don't have it at hand right now.

We also found other images with same artefacts, but for the most part, the images do not exhibit this (airplanes are in white color, as they should be). My question is, is this can be fixed, is it some kind of postprocessing artefact or is simply the error in acquisition that cannot be fixed post acquisition?

Another question: having the image ID, how can one find this image via planet.com's web page? We are preparing a metadata-dataset that would not contain images, but will refer to image ID, allowing the researchers to download exactly the same data after they get subscription to Planet.com.

Another question, who do I contact regarding the Educational and Research Program? Where do we send published papers, etc? Or ask further questions regarding the dataset?

0

Comments

3 comments
  • Janez Pers

    105c is one of our "next generation" PlanetScope satellites and uses a different sensor architecture.  There is some non-technical information on these new satellites at https://www.planet.com/pulse/introducing-next-generation-planetscope-monitoring/ but briefly they use a "multistripe" architecture where we are actually assembling a "scene" from chunks of different images collected over a second or two.  This particular class of satellite can be identified in the data api as having "instrument": "PS2.SD".

    The issue of time difference can also be seen in our classic imagery if you compare the NIR band to the RGB bands.  In the old architecture the NIR is assembled from nearby scenes, but the RGB is collected instantaneously so there is no time difference in those component acquisitions.  

    This sort of multistripe architecture is common, and we see similar artifacts in RapidEye and SkySat imagery which also acquire different radiometric bands at slightly different times.  So this is not a processing problem, and it will generally happen in many imagery products for fast moving objects like planes. 

    As you observed, with some modelling it is even possible to deduce the speed of fast moving objects based on these artifacts. 

    I'm sorry, but I don't have a suggestion on how to refer to a web page for a particular scene.  But if you are clear in your metadata about the item-type, item-id and asset name, it should be fairly easy for others to fetch the same product. 

    Best regards,

    Frank (Planet Pipeline Engineer) 

     

     

     

     

    0
  • [quote]But if you are clear in your metadata about the item-type, item-id and asset name, it should be fairly easy for others to fetch the same product. [/quote]

     

    Thanks for all info, that helps us a lot. Are there any written instructions/docs about fetching the product when knowing the above info? Actually web page/url is not needed, but some instructions would be welcome. Do we need to go through API? In any case we will have to write instructions for others how to do this, so any pointers to information would be very welcome.

    In case of the API, does this apply: https://developers.planet.com/docs/orders/ordering-delivery/

    I assume we can create POST request, containing all needed assets. And then these researchers submit via curl when they have an account.from Planet, right?

    0
  • Janez,

     

    I would normally use the item type, item id and asset to download from the data api.  For instance this url:

     

    https://api.planet.com/data/v1/item-types/PSScene3Band/items/20160929_023611_0e0f/assets/

     

    shows you the assets available for item id "20160929_023611_0e0f" of item type PSScene3Band.  If you wanted the "analytic" asset you would follow the download or activate links on the document returned by the above link.

    You should also be able to order via the orders api, but I think it uses bundle names which are an abstraction around groups of assets.  

     

    Best regards,

    Frank

    0

Please sign in to leave a comment.

Didn't find what you were looking for?

New post