| Table of Contents | ||||||
|---|---|---|---|---|---|---|
|
...
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.
...
All bands need to have the same size. If they have different sizes, you need to resample them to a common size. You can use the resampling operation to do this.
Why are RGB Images differently colorised and not comparable?
The different results of the RGB image creation results from the process how SNAP creates images.
The value range of a band is taken and clipped by 2.5% at the upper and lower end of the range. This is done to remove outliers.
But still the ranges can vary from image to image. SNAP now uses this range to create the image and creates the colour stretch. This leads to the different results.
You can overcome this by changing the colour stretch in the Colour Manipulation tool manually.
Another way of doing this is to clip the values already in the expressions of the RGB profile.
For Sentinel-2 the suitable expressions could look like:
blue=B2 < 0 ? 0 : B2 > 0.25 ? 0.25 : B2green=B3 < 0 ? 0 : B3 > 0.3 ? 0.3 : B3red=B4 < 0 ? 0 : B4 > 0.35 ? 0.35 : B4
For Sentinel-3 OLCI one could use these:
blue=Oa04_radiance < 0 ? 0 : Oa04_radiance > 430 ? 430 : Oa04_radiancegreen=Oa06_radiance < 0 ? 0 : Oa06_radiance > 430 ? 430 : Oa06_radiancered=Oa09_radiance < 0 ? 0 : Oa09_radiance > 430 ? 430 : Oa09_radiance
Here you can download the pre-defined profiles. You can load them into SNAP when creating an RGB image and save them for later use.
Actually, the same issue with varying colourisation applies to grey scaled images and not only to RGB images. Here you can use the Colour Manipulation tool to harmonise the image creation.
How to move the `.snap` directory to a different location?
...
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
...