Inquiry regarding the extraction of pure vegetation pixel reflectance for LUT generation in DART

[喻盈昕]

Dear DART Team,

I hope this email finds you well.

I am a researcher currently using the DART model for vegetation parameter inversion. First of all, I would like to express my sincere gratitude to the team for developing such a powerful 3D radiative transfer model; it has been instrumental in my research work.

Currently, I am working on constructing Look-Up Tables (LUTs) for the inversion of chlorophyll content (Cab) and Leaf Area Index (LAI). During this process, I have encountered some technical questions regarding reflectance extraction and would appreciate your expert guidance:

When simulating complex forest scenes or spatially heterogeneous landscapes, the reflectance images output by DART typically include a mixture of vegetation, soil background, and shadowed areas. To improve the accuracy of the inversion, I would like to extract the reflectance of "pure vegetation pixels" only to generate the LUT, rather than using the average reflectance of the entire scene.

Specifically, I have the following questions:

1. Does the DART interface or configuration file provide a direct option to export spectral data and generate LUTs specifically for certain species or voxel types?

2. If this needs to be implemented via pytools4dart or other post-processing tools, does the team recommend a specific method for mask extraction or categorical statistics?

I would be extremely grateful for any operational suggestions, documentation links, or sample code you could provide.

Thank you for your time and assistance. I look forward to hearing from you.

Best regards,

Yingxin YU

[Jean-Philippe Gastellu-Etchegorry]

Dear  Yingxin YU,

Thank you for your kind message. Indeed, we do our best to help scientists. 

It seems that what you want can be readily provided by DART. For that, you need:

- To ask for products per type of scene element after having selected the types you want in DART.

- To set the product "Per type of scene element in the definition of the LUT. 

If needed, I can send you a small example of DART simulation that illustrates the above mentioned options. Please, let me know.

Best regards

DART Team

[喻盈昕]

Dear DART Team,

Thank you very much for your quick reply and detailed explanation. I really appreciate your support.

Yes, I would greatly appreciate it if you could share a small DART simulation example demonstrating the options you mentioned. This will help me better understand and implement the settings for generating products per type of scene element in the LUT definition.

Thank you again for your kind help.

Best regards,

Yingxin YU

[Jean-Philippe Gastellu-Etchegorry]

Dear Yingxin YU,

I will prepare it and send it to your private Email. Hopefully, it will fulfill your expectations. 

I will probably reply in 2-3 days because I am presently in the waiting room of an airport. 

Best regards

DART Team

[喻盈昕]

Dear DART Team,

Thank you very much for your assistance.

I aim to generate a canopy reflectance look-up table (LUT) for a forest scene under different LAI values. I have followed your instructions: I enabled the option “Per type of Earth scene element” in the LUT definition, constructed a forest scene with five trees, and successfully generated the full‑scene LUT file.

However, I am encountering two issues:

I'm not sure how to export the LUT for the vegetation element only. Currently, I only have the LUT for the entire scene.

• Some LAI values failed during LUT generation, as shown in the attached figure. I am unsure what causes these simulation failures.

My project files are attached for your reference. Could you please provide guidance on these two points?

Best regards,

Yingxin YU

[Jean-Philippe Gastellu-Etchegorry]

Maybe, you did not notice my previous Email: I am preparing something for and will send it to you in 2-3 days. 

Best regards

DART Team

[Jean-Philippe Gastellu-Etchegorry]

Dear Yu Yingxin, 

Please find a documenyt that summarizes how to get images per type of scene element. The document contains the link to the simulation (link valid for 15 days). In the coming days, hopefully, I will send a result with the LUT. 

Best regards

Jean Philippe 

[李伟华]

Dear Yingxin Yu,

You can send private message to me.

May be I can help you in chinese.

Best 

Weihua

[喻盈昕]

Dear Prof. Jean-Philippe,

I am writing to report an issue I encountered in DART 5.11.0 (build V1457).

When using the Sequence tool to simulate reflectance under different LAI values, some steps failed to generate any output. When I reran the sequence, some previously missing LAI steps were generated successfully, but others remained missing.

Best regards,

Yingxin Yu

[Jean-Philippe Gastellu-Etchegorry]

Dear Yingxin Yu, 

Thank you for your message. Can you send me your simulation (if it is "large", maybe the input folder and the sequence file are enough). 

Best regards

Jean Philippe