Pixel values

snap
#1

Dear Sir/Madam,

I am studying to use SNAP for InSAR Process.
I am confused that when I extract the pixel value by “Copy Pixel-value to clipboard”, the value is too high, for example, 170653499392.00000, I don’t think this is the right value.
So, would you please do me a favor to solve this problem.
Thank you!

Yours,
Dingfeng Duan

--------------------------------Example----------------------------------
Product: coregistration_ML

Image-X: 229 pixel
Image-Y: 1249 pixel
Longitude: 78°51’51" W degree
Latitude: 35°50’06" N degree

BandName Value Unit
**i_HH_mst_14Nov2008: -72358.76563 real **
**q_HH_mst_14Nov2008: -228400.25000 imaginary **
**Intensity_HH_mst_14Nov2008: 170653499392.00000 intensity **
**i_HV_mst_14Nov2008: 9289.46777 real **
**q_HV_mst_14Nov2008: -76324.45313 imaginary **
**Intensity_HV_mst_14Nov2008: 22068191232.00000 intensity **
**i_VH_mst_14Nov2008: 13771.38867 real **
**q_VH_mst_14Nov2008: -48963.98828 imaginary **
**Intensity_VH_mst_14Nov2008: 14359399424.00000 intensity **
**i_VV_mst_14Nov2008: -24287.24609 real **
**q_VV_mst_14Nov2008: -168038.34375 imaginary **
**Intensity_VV_mst_14Nov2008: 106561978368.00000 intensity **
**i_HH_slv1_30Dec2008: -78779.34375 real **
**q_HH_slv1_30Dec2008: 23701.58789 imaginary **
**Intensity_HH_slv1_30Dec2008: 174779187200.00000 intensity **
**i_HV_slv2_30Dec2008: 65015.83984 real **
**q_HV_slv2_30Dec2008: 37498.47266 imaginary **
**Intensity_HV_slv2_30Dec2008: 11097473024.00000 intensity **
**i_VH_slv3_30Dec2008: 85328.28125 real **
**q_VH_slv3_30Dec2008: 23100.89453 imaginary **
**Intensity_VH_slv3_30Dec2008: 17368834048.00000 intensity **
**i_VV_slv4_30Dec2008: -292553.62500 real **
**q_VV_slv4_30Dec2008: 77121.69531 imaginary **
**Intensity_VV_slv4_30Dec2008: 119217430528.00000 intensity **

**latitude: 35.835133 **
**longitude: -78.86406 **
**slant_range_time: 5030339.0 **
incident_angle: 23.277449

#2

why do you think it is too high?

#3

Which kind of values, do you intend to extract, your example is corregistered Multilook SLC images, master and slave, have two types of information amplitude and phase, firstly you should define the pixel value of image you want to extract is resulted from which process steps, then you could easily extract the pixels’ value of certain results.

#4

Thank you for your consideration!
I used the PolSARPro to extract the [S] matrix and the [T3] matrix, the pixel value of each pixel is less than 2. I think this is more resonable.

#5

I am very glad to receive your reply!
Thank you!
I want to know the true value of the pixel in the SAR image.
The real value of real part and the real value of the image part.
When I use the SNAP to open one ALOS-PALSAR file, the pixel value is so high.
However, when I use PolSARPro to extract the value of each pixel, the value is always under 2.
This differece confuses me.

#6

Using different software doesn’t change the reality of pixel values, I don’t know how do you extract the values in both sw. Would you please to share an example of both with screenshot!

#7

I am not extracting the values directly. I just check the values.
In SNAP, I use the function called “Copy Pixel-value to clipboard” to check the value of the pixel.
In PolSARPro, I extract the [S] matrix, and then I use the ENVI to open the data such as s11.bin, then I use the tool called “Cursour value” to check the value of the pixel.

#8

Is it an option to compute the S matrix directly in SNAP?

#9

No. I use the PolSARPro 5.1.3 to do this.

#10

but you know that you can do it in SNAP as well? This was my suggestion, sorry if I misunderstood your point.

#11

Really? Please teach me. Thank you!

#12

You can import most of the common SAR satellites into SNAP using File > Import > SAR sensors

Then you conduct a calibration Radar > Radiometric > Calibrate (make sure to check “complex output” in the second tab.

Then you select Radar > Polarimetric > Polarimetric Matrix Generation > S-matrix

#13

Hi, I also encountered the same confusion, do you understand the reason?