Getting oil spill bit mask in snap from SLC product


#1

Hello all,
i am regular user of ESA products. Now i am also using sentinel -1 A datasets.
while using the SNAP tool, i am facing issues in viewing the oil spill bit mask/ship detection. even though i followed the necessary steps with different threshold shifts. But i did not face this issue while using NEST.

issue :

i tried overlaying the bit mask over the image. but it was not visible. i tried with different thresholds too.

Could you please suggest on this.

Thanks !!


Steps for Oil Spill Detection
Download product to do oil spill detection
#2

have you checked if the bit mask consists of data?
You can check in the pixel info tab


#3

Hello ABraun,

Thanks for the response. The bit mask does not have any intensity/amplitude rather, it shows only the geographic co-ordinates

Thanks
sjp


#4

NaN means that no data was written and something went wrong.

What data did you use? Which steps did you undertake so far?


#5

i have used the subset_1_of_S1A_IW_SLC__1SDV_20170129T003131_20170129T003158_015039_01892E_2C18_deb.data

i have carried out the debursting, elipsoid correction, geometric reprojection, calibration and speckle filtering. after this i did, oil spill detection which generated the oil spill bit mask.


#6

Can you try leaving out reprojection?


#7

i have tried without reprojecting the dataset, then also, i could not able to find the amplitude and intensity values.
Actually, while performing the ellipsoid correction, it was automatically georeferenced. but while doing the terrain correction, the georeference is not occurring.moreover, i have noticed that, if i am taking a subset, the source bands are missing.
so i have to process the entire dataset, which is consuming a long time.once after, bursting, EC, i have performed the oil spill detection,but it has not shown any bit mask.


#8

Ellipsoid correction and Terrain Correction both project the data into the chosen coordinate reference system.
Terrain Correction probably leaves an empty outbut when the checkbox “Mask out areas without elevation” is checked.

As no SRTM over ocean bodies is available, nothing can be terrain corrected.

As long as you don’t perform calibration, amplitude or intensity should always remain in your product.


#9

where i can see this settings, while making EC/TC?
while taking a subset, these bands are captured. while doing the oil spill detection, error mesage appears as “the file parameter was not set” why so ? i have followed the manual procedures, but now where is the bug?
could you please suggest me other TOOL/ways to achieve oil spill bit mask ?


#10

in the second tab, Processing Parameters

Can you post which data are you using? It’s not that hard…


#11

i have posted the data. Please find below the gdrive link, which has the debursted data. However, i could not able to attach the original dataset.
https://drive.google.com/open?id=0B-efZ5fzVzhARmExTkVicFVaakE
Here, after debursting, i subjected it to oil spill detection tool. After the completion, i could not able to find the mask.
If you have any detected oil spill bit mask(S), please share me the dataset.


#12

whether NEST tool can be used for sentinel dataset, i have not tried it.
Is it possible to make out/identify the oil slick with the amplitude/intensity values, if so pl. let me know.


#13

Didn’t see that, sorry. I’ll give it a try.
Did you consider using the GRD product instead of SLC? Should be sufficient for oil spill detection and you can skip the debursting step.


#14

yes, i have tried the GRD product too. unfortunately, it does not have amp/intensity
i am enclosing the same
https://drive.google.com/open?id=0B-efZ5fzVzhAOXRhUzExem0yczA
Please see this too.
i have deleted the downloaded zip/original file. however, all are extracted to a folder. Once after processing it, the original files are found missing, why so ?
Kindly suggest


#15

Sorry, what do you mean exactly?


#16

providing the *.dim file is not enough when you want to transfer data, the actual data lies in the folder with the same name. But I took the name from the metadata you provided to download it from https://scihub.copernicus.eu

  1. Open in SNAP

  2. Multi-Look (reduces speckle and lowers spatial resolution to 30 m which should be sufficient)

    result:

  3. Oil Spill Detection

  4. Geocode (only mask needed)


    result:

  5. Adjust colors and export to Google Earth

It’s not perfect. Maybe the Minimum cluster size (smallest oil area expected) has to be adjusted in the Oil Spill Detection module and speckle could be also filtered, but it technically works fine.


#17

Thank you.
Hope this belongs to GRD product ?
was the entire dataset subjected to oil spill detection, whether subset will work ?
calibration was also carried out. was it done with 0.1 sq.km cluster size ?
hope the oil spill detection tool will give only the dark spots .


#18

I made a subset, no calibration, cluster size 0.1 - just try it yourself.


#19

i tried the same with cluster size of 2sq.km of 2db shift. i obtained the results as follows

but please do the next image

in the second image, the black circle shows the oil reported zone. But the mask is not visible there, why so ?
even though the intensity is very less.

Moreover what are the other features reported as a dark spot , to the right of the oil spill zone. is that due to wave features ? how to interpret them?


#20

you can change the “Minimum cluster size” and the “Threshold Shift (db)” and “Background Window Size” and how the results changes.

Probably lowering the detection threshold would be most promising option.