Sigma0 VH/VV analysis

Microwave Toolbox
#21

you have to select the corresponding polygon with the normal mouse.

#22

Still doesnt work

cursor_selected
cursor_selected.png1919×961 129 KB

#23

did you again select it in the filter dialogue?

#24

yes sure, but still doesnt work. even if I select all bands, it is the same. It only works when the cursor on.

cursor_selected_filter
cursor_selected_filter.png1918×960 134 KB

#25

from your screenshot I see that it is still a virtual raster

#26

Sorry but I dont understand what I need to do. How can I solve this problem? Could you tell me step by step?

#27

I explained already above and based on your comments it worked: Sigma0 VH/VV analysis

grafik this indicates that your product is still virtual.

#28

Are you sure that it is still virtual? Because I already converted it before and now I think it doesnt seem as virtual. When it is virtual, there would be “V” symbol on the band icon as below, isnt it?

BANDS2

but when I right click on my band, it is like this:

BANDS

#29

you are right. Even after it is converted and saved there is “expression was”.

But it works anyways - I just tested it. I created a band “ratio” from VV/VH in 6 Sentinel-1 images.

ratio as point from cursor

image
image.jpg1663×920 1.02 MB

Switching from cursor mode to polygon mode (I imported a shapefile with two different polygons)
also ratio

image
image.jpg1661×920 1010 KB

Things to test if it doesn’t work at your side:

  • Make sure that the name of the ratio is consistent over all products.
  • Try importing the vector as a Shapefile instead of drawing it (and, again, save the product)
  • Import the shapefile into all used products.
#30

I think I am missing something but I dont know what.

If I made mistake about name or descriptions of bands, It even wouldn’t show when the cursor on. For this reason I thought that there are some problems due to shape files. I created another shape file and even I didn’t change the location of it. Then I imported it to all products and saved all products. Finally, I opened time series and tried again and again but unfortunately, It didn’t work.

Thank you very much for your help.

If any other opinions from you or others, please let me now.

#31

Hello,

I have sigma0 VH and VV values in an excel sheet. How can I calculate the VV/VH, VH/VV and (VV+VH)/(VV-VH) indices from these values? Can I simply subtract the 2 values for the ratio?

image

#32

Hi. These values are in dB (calculated using 10*log10(values not in dB)). So yes if you just want VV/VH or VH/VV you can just subtract the dB values. However if you want to calculate (VV+VH)/(VV-VH) than I suggest you convert the dB values to non-dB values and apply this equation.

1 Like
#33

Hi, ABraun! When I using band maths to create the absolute displacement band from the relative displacement band and a reference point, I put the band maths expression like “displacement_VV+0.00462”, and I success getting the absolute displacement band and I saved the file as you said!
But when I put all products in the “Time Series Analysis Settings” and click the “Filter bands” button, I got an error as follows. I have no idea what cause the error, any advice will be appreciated!

搜狗æˆȘć›Ÿ20210705223453
搜狗æˆȘć›Ÿ202107052234531272×817 223 KB

#34

Sorry, haven’t seen this before. I just know that the time series tool needs all products starting with the same term to be interpreted as parts of a series. Maybe the band maths result makes problems because the same date is now in the stack twice.

#35

Thanks for your reply! What makes me confused is the time series tool works well before I use the band maths, and the Java error just occurred after I add the absolute displacement band. I will try to solve “the same date is now in the stack twice” problem by deleting the relative displacement band, any details will be shown later.