Exporting Files out of SNAP correctly for ArcMap


#1

Hi there,

I have been able to create interferograms and unwrapped displacement images, however, I am having some issues getting these files into ArcMap correctly. It seems that it’s not just as simple as File > Export > Geotiff.

Can anyone give me a direct step by step to get my image results out of SNAP correctly so that they all show up correctly in ArcMap? I need to be able to perform analysis using interferograms, unwrapped images, and coherence images in ArcMap. I do not want to use Qgis.

Thanks in advanced for your help!


#2

You can load the img files in the data folder directly into ArcMap


#3

This should actually work. What’s the problem you observe?

If you already have BEAM-DIMAP files you can follow the suggestion of ABraun.
in the data directory you find img/hdr files which can be opend in ArcMap.


#4

It could be that neagtive values in calibrated images in db cause errors in the GeoTiff format


#5

Hello i have the some problem when i export file to geotiff the pixel value change for example the sigma0 should be between 0and 1 but when open the geotiff with QGIS i found that sigma with higher value ( 100 , 50 …)


#6

Does the sigma0 band have a scaling factor?
you can check this by selecting it in the Product Explorer and then Go to Analysis / Information in the menu.
If you see a scaling factor (different from 1.0) and/or a scaling offset (different from 0) you need to apply them.

In your screenshot you show the high values in SNAP. Is this a Geotiff file? Is this reloaded?


#7

Yes this is geotiff i reload it in SNAP .

the scaling factor =1.


#8

And how have you created this file. Did you write directly into geotiff or have you made a format conversion step.
Can you provide me this file?


#9

i write geotiff using conversion Datatype


#10

I’ve seen that you are still using old SNAP modules (5.0.0). There are updated ones.
Actually you should be regularly informed about updates in SNAP.
Please select Help / Check for Updates from the menu and install the updates.
Maybe this solves the problem. I remember some issues with the datatype conversion.


#11

i will try with the new version of snap , my question if the unit8, float 32 has an effect about the result of geotiff


#12

Yes this changes the values.

Your values between 0 and 1 are scaled to the new min (0)and max (511) values.
That’s why you get those high values.
Just skip the data type conversion and your values should be fine.


#13

YES just change of unit8 with float 32 solve the problem thank you @marpet


#14

I have a few interferograms created. The last step I applied to each image is the Goldstein Phase Filtering. Exporting these images to Geotiff works, but they don’t open in ArcMap. ArcMap says “Invalid raster dataset. Failed to create raster layer.”

How do I get these interferograms to open and show up in the correct spot with the correct orientation in ArcMap? I understand that due to the aquisition orientation, images can be flipped and/or mirrored. In other interferometry software I have used, I have to take extra steps to get these images to show up correctly in ArcMap. I think there are more steps in SNAP that need to be applied, but I haven’t done this before, so I am not sure what needs to be done.


#15

if you want to display SAR data in ArcMap your last step should always be Range Doppler Terrain Correction. This adds a projection to your data.
You can also directly open the img files from the data folder in ArcMap instead of conversion to GeoTiff. This avoids possible conversion errors.


#16

Yes, that worked perfectly. Thanks. I did see an example of this in a tutorial yesterday too that said the same thing, but had another step. Raster > Geometric Operations > Reprojection. I don’t see why this part has to be done unless you want to export to kmz for a quick view in Google Earth. Do you guys agree?

I have also unwrapped my images, but having an issue viewing the result also. I understand that to unwrap, you have to use snaphu export, then import the result back in. Here is a picture of my exported files using snaphu:

Snaphu Import asks for certain files in each tab, which files do I choose for each tab? What I am doing isn’t working:

1-Read-Phase - Source Product Name: ?
2-Read-Unwrapped-Phase: ?
3-SnaphuImport: Do I check that box? (Do NOT save Wrapped interferogram in the target product)
4-Write: Target Product Name: Target? (I can call it whatever I want right?)

Thanks so much for your help! I know this is pretty easy in concept, but for some reason this step is not working right for me.


#17

reprojecting makes no sense to me as well.

Exporting and importing is not enough, you have to create the unwrapped phase before importing. Please have a look at my tutorial:


#18

Thank you very much, I will have a look and circle back if I have any specific questions.

Do you offer classes online somewhere? I have been doing interferometry for years, but this is the first time using the SNAP software. I would love to learn more advanced skills, tips, tricks with this software. Let me know if you offer anything else you think would be helpful through my journey.

I really appreciate you!


#19

I’m glad I could help.
I’m not offering any courses at the moment, I am just a SNAP user who learnt it by myself.


#20

Gotcha. Well this forum has been great so far. I’ll just keep using this and a few friends around the world who use it too.