Right processing workflow for TRDRs and others

[Wladimir Acevedo]

Hi community, 

I'm working with ENVI 5.3 + IDL coupled with CAT 7.4 trying to process TRDR images (.trr3). I'm based primarly on the CRISM data processing workshop from 2012 and 2017 and my worksteps are as follows:

1.- Apply the ATM  corrections with CAT to the images
2.- Apply de map projection fo the image
3.- Obtain the summary parameters image

Nevertheless, I have certain doubts about this, so I would be very grateful if you can provide me some help please. My questions are:

- Should I obtain the summary parameters and then apply the map projection or it is the opposite?
- It is necessary the "ratioing" for the spectra and use the "Flatten summary parameters" option?. I've seen a post where its says that is enough the "Continuum Removed" option
- How can i obtain a better resolution for the summary parameters image?. I've seen very good resolution images from papers that doesn't look like what I have obtaining (img_1)
- When I create the summary parameters image  the spectra doesn't look like the TRDR pure image because the data values change. Does that mean that I have to use the spectra from the TRDR and the summary parameters image is just like a "color guide" fot the mineral phases? (img_2)

Finally, how can I use the summary parameters properly and elaborate mineralogical maps from they?

Any help will be very appreciated, thank you.

Wladimir
wladimiracevedo@udec.cl

img_1: The resolution that I'm getting from the summary parameters image after the custom stretch

img_2: Spectra for the summary parameters image vs the original TRDR corrected image from the same pixel on both.

[Feng]

Hi Wladimir,

 

This is Feng, I will try to answer your questions:

Should I obtain the summary parameters and then apply the map projection or it is the opposite?

Basically they are identical. For my opinion, I will do map projection then summary parameters since it reserves the summary parameters band name.

It is necessary the "ratioing" for the spectra and use the "Flatten summary parameters" option?. I've seen a post where its says that is enough the "Continuum Removed" option

Sorry I don't understand this question. I will take the team scientist about this.

 

- How can i obtain a better resolution for the summary parameters image?. I've seen very good resolution images from papers that doesn't look like what I have obtaining (img_1)

The summary parameters doesn't change the resolution. For this product, it is 18m/pixel.

Here is all CRISM EDR resolution:

https://ode.rsl.wustl.edu/venus/pagehelp/quickstartguide/index.html?crism_edr.htm

For some Along-track oversampled (ATO) Spatial pixels unbinned for target – 18 m/pixel cross-track, up to ~3 m/pixel downtrack, requires special processing for increased resolution; half swath length as above.

For img-1, if you only select one band (BDI1000IR), you can see

 

When I create the summary parameters image  the spectra doesn't look like the TRDR pure image because the data values change. Does that mean that I have to use the spectra from the TRDR and the summary parameters image is just like a "color guide" fot the mineral phases? (img_2)

Yes. For your attached Img-2, the index is not the wavelength but the summary parameters band:

Finally, how can I use the summary parameters properly and elaborate mineralogical maps from they?

For the summary parameters, you can read the following paper:

Revised CRISM spectral parameters and summary products based on the currently detected mineral diversity on Mars

https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2014JE004627

 

Hope this helps.

 

Thanks,

Feng