As a part of my project proceeding, I have encounter with an issue which I tried to solve but I couldn’t. Hereby I would like to inform you that in Wind Field Estimation using SNAP software tool, the wind direction is indicating in two headed arrow mark. I could not understand how can I find the exact wind direction with one headed arrow mark. It is my pleasure if I get the procedure to rectify this problem. Kindly help me to get rid of this. Thank you
Here is the product which I am using for my case study- Refugio Oil Spill, north of Refugio State Beach in Santa Barbara County, California.
Product: S1A_IW_GRDH_1SSV_20150531T015813_20150531T015838_006159_008023_EF9E
You need external data, for example a weather-report, to remove the 180-degree ambiguity. Is this not explained in the help, I think the info should be there?
Thank you for your kind reply. Yes, I went through the SNAP help menu but didn’t find any method or process to remove the 180-degree ambiguity. Can you please clarify, what kind of external data require to remove the 180-degree ambiguity?
Thanks once again for your kind help. If you help me for the final time I would be thankful. Please just help me from where can I get the weather forecast information (on general wind direction) for below sentinel 1 data for the same date and place.
I was also looking at the oil slick there using S1a - did you get a good result with the oil slick detection? I was not happy with mine. I would love to hear what steps/parameters you used if it is something you don;t mind sharing.
Even I was not happy with mine too. I tried with different parameters to get good results but the results were not satisfied. Better try to use these parameters may be you get better result as I tried for different case study, somewhat got good result.
Following criteria has been fulfilled for the detection of the Oil Spill:
Source Product: Oil Spill detection
Source Bands: Sigma0_vv (With checked out Mask out the land* box).
Background window size : 20
Threshold Shift: 2.0(dB)
Minimum Cluster Size: 0.1sq.km
I asked on the forum a few weeks back - a larger window size (512+) seems to help. I tried again with an ENVISAT image of the deepwater spill and it worked ok. i still wasnt happy with results froma smaller spill like refrugio so i was wondering what i am missing…
Have anyone got single headed arrow in wind field estimation process. Please kindly help me, I am not getting any solution for to make double headed arrow as single headed arrow. As I downloaded external weather report data but i can’t use that in SNAP to make it as single headed arrow.
There might be a neater way to do it but what i was going to try was:
if I could find the wind results xml file that they refer to in the manual (i cannot find the file on windows- have searched everywhere)
use a link similar to the one I gave above for Refrugio to find the correct wind direction (remove the 180 ambiguity).
then either delete the incorrect dx:X or dy:Y wind value or if it requires one, make it the same value.
replot the results
From the manual:
Wind Field Retrieval Result Report
The wind field estimation results are saved into an xml file .s1tbx/log/wind_field_report.xml with the following information given for each window in which wind estimation is made:
lat: Latitude of the central point in the window.
lon: Longitude of the central point in the window.
speed: Estimated wind speed in m/s.
dx: X component of the estimated wind vector.
dy: Y component of the estimated wind vector.
Dear irshadnagur，
When studying wind field estimation in here, I accidentally saw your problem. You mentioned that you also studied oil spill detection. Could you please share me more information about the oil spill accident information of this product（Product: S1A_IW_GRDH_1SSV_20150531T015813_20150531T015838_006159_008023_EF9E）?