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How should I cite SNAP?
If you want to cite SNAP you can use the following suggestion:
SNAP - ESA Sentinel Application Platform v{LATEST-VERSION}, http://step.esa.int
A specific Toolbox can be cited like:
S1TBX - ESA Sentinel-1 Toolbox v{LATEST-VERSION}, http://step.esa.int/
Just replace {LATEST-VERSION} with the actual version, e.g.
SNAP - ESA Sentinel Application Platform v6.0.7, http://step.esa.int
S1TBX - ESA Sentinel-1 Toolbox v7.0.1, http://step.esa.int/
What to include in a forum post when reporting an issue?
Before you open a new topic, please use the search function of the forum to check if your problem is already discussed in existing topics. To keep the forum structure clean, please consider continuing discussions in existing topics before creating a new topic on similar issues. Once your post has been submitted, the corresponding topic will automatically be visible at the top of the topic list.
When reporting an issue, try to include as much information as possible to allow developers to reproduce the problem including:
Toolbox version and operating system, amount of RAM
Identify the relevant satellite products by giving the full name of the product
List the exact processing steps needed to recreate the issue
Attach relevant screen captures and resulting images (copy and paste function)
Attach the log file to your post. You can find it by selecting from the menu Help / Show Log Directory.
Make sure to reproduce the error first and then attach the messages.log file.In case you processed a graph file, please upload the XML as well (using the upload button)
It also helps to understand when you shortly describe your overall aim (e.g. water change detection, vegetation monitoring...)
In case you get an error message, please include it in your question (again, please also check the search function if this error message has already been reported/solved)
If you work with multiple products, please mention if the error occurs for all of them or just for one specific product.
What does the “dl” unit mean?
The dl means dimensionless. The variable has no unit.
https://en.wikipedia.org/wiki/Reflectance#SI_radiometry_units
How to create an RGB composite from individual bands?
When having 3 data products with the individual bands for the channels of the RGB image you want to create, you needed to reference the products in the expressions of the RGB Image creation dialogue.
Right-click on one product and select “Open RGB Image Window“. In the example image, all bands have the same name ‘band_1' and you have to reference the correct product for the channels. Each product has a reference number which you can see in the Product Explorer. To reference ‘band_1’ in product 2 use the expression '$2.band_1'.
That’s the quickest way.
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Please select the band in the Product Explorer and select from the Menu > Analysis > Information. Please carefully check the entries on
Geophysical data type vs. Raw data type (how SNAP displays the data vs. how the data is actually stored, e.g. Sentinel-2 bands are stored as 16-bit integers (full numbers), but displayed as 32-bit float (decimal values)
Scaling factor and Scaling offset (the factor defines if the actual pixels are multiplied by a constant, e.g. Sentinel-2 bands are multiplied by 1.0E4 (divided by 10000) so the pixels are displayed as reflectance between 0 and 1)
No-data value (defines which pixels are displayed transparently in SNAP)
Valid-pixel expression (allows to mask out pixels in SNAP according to a logical or mathematical expression)
→ All these definitions are only valid in SNAP and not considered when exporting to GeoTiff or other external formats. They must be taken into consideration accordingly.As every external format has its own specifications on the maximum file size and detail, conversion errors can occur (e.g. 16 bit (0-32786) before conversion vs. 8 bit (0-255) after conversion).
Related questions
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Please also have a look at this tutorial: Export of products from SNAP
Related questions
Why should I stick to the BEAM DIMAP format as long as possible?
I want to use a product processed in SNAP in another software
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In order to write intermediate results to disk you need to add the Write operator to the graph. For the final result a Write operator is added automatically to the graph by gpt. So, all you need is to specify the target on the command line.
How to best batch the gpt e.g. using just DOS-batch or using python
For batch processing there is an example available in our SNAP wiki.
For python there are meanwhile some examples available in this forum. Probably reading this thread (Example script for multiple operations?) will help you.
But you can also do batch processing from the Desktop application. See in the menu at Tools --> Batch Processing.
It depends on you what you like most.
Related questions
Are there recommended graphs or example graphs available?
Recommended graphs can be found in the Graphs menu of the Graph Builder.
Related questions
A process related to digital elevation models is taking forever to finish
In January 2021 the source for SRTM 3Sec data which are automatically downloaded by SNAP has changed. Since then, SNAP tries to access the resources, but cannot find them any longer. This affects the following tools:
Range Doppler Terrain Correction
SAR Simulation and SAR Simulation Terrain Correction
S1 BackGeocoding
Topographic Phase Removal (also contained in Interferogram formation)
Orthorectification
Land/Sea Mask
Add Elevation Band
and potentially other operatos which try to acceess digital elevation data, for example like this
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This will be fixed by an update soon which leads SNAP to the new location of these data. Until then, you can help yourself by the following solutions:
Option 1: Select SRTM 1Sec (AutoDownload) instead whenever possible. These should work regardless of the location of SRTM 3Sec data.
Option 2: You can tell SNAP the new location of the SRTM 3Sec data like this:
Go to your SNAP installation directory (e.g. C:\Program Files\snap) and go inside the ect folder where you find the file
snap.auxdata.propertiesOpen it with a text editor (maybe needs administrator privilleges) and go to line 27 which defines the location of SRTM 3Sec data. Change it from
DEM.srtm3GeoTiffDEM_HTTP = http://cgiar-csi-srtm.openterrain.org.s3.amazonaws.com/source/
toDEM.srtm3GeoTiffDEM_HTTP = http://srtm.csi.cgiar.org/wp-content/uploads/files/srtm_5x5/TIFF/Save the file and restart SNAP.
The processes should then work again. If you still encounter issues, it might be that SNAP has already downloaded parts of the file but could not finish the download, leading to incomplete or corrupted files. You can solve this by manually deleting them. You find the automatically downloaded digital elevation models in your user directory (user\.snap\aux\dem\SRTM 3Sec) where zip files are stored (e.g. srtm_35_05.zip). Once you delete all of them, SNAP will re-download all tiles required for the processing of an product, and the process should finish as usual.
S1TBX
What SAR missions are supported?
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