I made average scenes for a period of 3 months. Before that, for all the scenes I did:
4.Linear to DB
Also, I used Slice Assembly for two scenes, when there was a need (right after download scenes).
If I use the following formula, I do not get a rgb image.
I see that both are different, but I don’t understand what you mean by “natural look”. Can you please post a link to the source of the second image?
Maybe you can adjust the contrasts in the color manipulation tab to get closer to the image shown below.
As microwaves are not related to color it is unlikely that you find an RGB configuration which looks like an optical image. You can, however, play around with the contrast of the three channels to create balanced colors.
What is the best way to remove the speckle?
I used the Speckle filter and the average of scenes for a period of 15 days, a 1 month and 3 months. Based on this, I see that the average of scenes removing speckle, but not completely. Is there another way to eliminate speckle?
Can I do a preprocessing of scenes for a period of 3 months (3.01.2017. - 28.3.2017.) and get a scene(average) so that when I zoom in at the level of the field, I clearly see the boundaries (approximately google earth). Is this possible with these footage?
Step of preprocessing:
3.Thermal Noise Removal
5.Speckle Filter (Filter: Lee Sigma, Windows size:7x7, Sigma:0.9, Target: 3x3)
I’d say this is quite good for a three month average. The only thing to test would be the effect of the different multi-temporal filter types. Some enhance finer linear structures while others are more aggressive but create a very smooth image.
The IDAN filter is based on region growing so if you are interested in the forest area you might check it as well.
You might like to know that the quick-look images included in the S1 products (file quick-look.png) is generated using the DN amplitude values in dual-pol products to give blue water and green land for most products:
Assign RGB channels. Red = co-polarisation amplitude, Green = cross-polarisation amplitude and Blue = Green/Red
Multiply the amplitude of the cross-pol image by 2.3
Multiply the amplitude of the RGB channels: Red: 0.891, Green: 1.209, Blue: 66.300
Since you are using sigma0 rather than DN you will need to adjust the values in steps 2 and 3.
You are degrading the resolution of your result by doing speckle-filtering before averaging in time. Since averaging many scenes gets rid of speckle anyway you should drop the speckle-filter, or filter the average-image afterwards (but that will again degrade the resolution)