Landsat 8 Pan-sharpening and clipping in ArcGIS 10

[Norman_Nash]

I am currently working with Landsat 8 imagery and an having a hard time pan-sharpening the imagery to get a better resolution.  Then option under properties>pan-sharpening to choose an infrared image as the 4th band is greyed out.  I am not sure if I am going about this right.  Should I create an new mosaic dataset first, then a natural color image and follow that with the pan-sharpening?  Any tutorials on this would help.

Second question is, when I clip the raster image from the study area boundary, the color of the pixels changes.  How do I prevent this discoloration and maintain the natural color of the pixels?  My analysis is dependent upon the pixels maintaining their natural color.  Any help would be appreciated.

[NICOLAPEDDIS]

You and Cody  are right about Landsat 8, the right true color combination is 4/3/2. But you didn't wrote that you was using LS8 instead LS7, so i wrote the right combination for the LS7

[CodyBenkelman · Accepted solution]

Norman

1) re: clip and color changes, yes your understanding is correct.  try that, and if you're still seeing a color change, then we have to figure out what's wrong.  You are correct in expecting that you should be able to see exactly the same, before and after...  HOWEVER, I'd put this on hold until you consider other advice - I'm not sure you should use "clip" on anything before perhaps a final, classified raster...  ( If you "clip" you end up with an exported version of the imagery and will typically lose connection to the metadata, and that metadata is critical for doing classification).

2)  I'm glad you're on 10.3.1!  That is the good news...  The bad news is, I think you should start over re: workflow.  There's no need to copy pixels into a GDB - it just duplicates data and may break the link to original metadata.  When you have time to read, I'd encourage you to learn more about the Mosaic Dataset and understand alternatives by reviewing our “Image Management Guidebook”  =  http://esriurl.com/6007   but that is not a very direct answer to this question...  What I would recommend is

1. for working with an individual image, you can use the Raster Product (expand the little satellite icon in Catalog) - you'll see the Pan Sharpened output is prebuilt for you

1. (A second #1.  I love auto formatting)  If you're working with multiple images, create a mosaic dataset, then when you  "Add Rasters" be sure to use the Landsat 8 Raster Type.  That will add function chains to derive the pan sharpened product automatically.
2. You can also use the supervised classification tools directly on the mosaic dataset (but NOTE pan sharpened imagery is NOT appropriate for classification...)
3. note all of your work will be done "on the fly" (without duplicating disk space) so when you get a good classified result, you can either export it, or just save the MXD to return to the output products you create.
4. I think I had a fourth recommendation but need to run to another meeting - my apologies - I will revise this or add a follow up post as possible...

Cody B.

[Norman_Nash]

Cody,

Thank you very much for helping me out. I really appreciate it.  I will read up on mosaic datasets and chat with you later to let you know how everything goes.  This online school is tough and have had more luck with responses on this blog. 

Norman Nash

[Norman_Nash]

Cody,

I have another question for you.  I did all that you said and the images seem to come out as they should.  I have a limited space on the server, which the ArcGIS is on via school.  When I export the Natural color image, NDVI, and composite images they seem fine while I am in ArcGIS.  I save under the specified folder and try and reopen and no images that I created exist (except a black screen).  The NDVI image is the only one that I can view in the TOC.  All others are black.  Is there a way to compress these so that I can not use up all the storage on my Drive?  Sorry for all the questions.  Also, my 2014 imagery seems to be brighter than the 2015.  These were taken around the same time (one in July 2014 and the other in August 2015).  The August image for 2014 was blown out because of cloud coverage so...  I would love to send you some screen shots of the images that I created but they cannot be viewed for some reason. 

Norman Nash

[CodyBenkelman]

Norman

Do you have a professor for this class?  It seems he/she would be the place to start with some of these basic questions. 

re: Export, there is a setting that can automatically promote your images from 8 to 16 bits, and then when loaded they can appear black.  Go back to Export, and see if the "NoData" value is shown as 256.  Alternatively, when you load an image, if you select it in the IAW and then turn on the checkbox for "DRA" (Dynamic Range Adjustment) that should show imagery.  If it is still black, then something went wrong with the export process. 

As for compression, yes, if you export TIFF format you can set it for JPG compression inside the TIFF file.  That can probably reduce your file size by 5x or more.

Last, what are you going to do with the exported images?  As a reminder, the mosaic dataset and/or IAW can generate RGB views, NDVI, classified images, etc. as layers "on the fly" so if you save the MXD you can always reload and recall those images - but if you don't need to transmit them to some other location, do you really need to export files to disk?  (If this is a requirement to submit as homework, I assume the instructor must have disk space to receive your exported files - you may have to export and then transmit one at a time if your disk space is severely limited)

re: the brightness difference between the two dates, if you have verified that there is no stretch being applied, I would assume the apparent difference is a real difference in energy received by the satellite.  Landsat is well calibrated so it won't be a sensor error.  One date may have had a high cirrus layer that diminished the incoming solar radiation, or alternatively, depending on the ground cover and which spectral bands you were viewing, there may have been a difference in vegetation brightness (% reflectance). 

Cody B.

[Norman_Nash]

Thank you Cody.

I am actually working on my thesis and chose this subject because I find it applicable in many aspects.  I am in my final stages of my thesis via USC and am diving into the processing of the imagery.  I have an advisor whom is new to the university but not very prompt with replies.  My previous RS professor at USC resigned and I am stuck on my own as of now-until I get some type of response.  I am sorry for bothering you but have not worked with imagery like this.  In our class, everything was set up as "easy to teach"-not learn.  I would design this differently considering my position right now. 

As for the "on the fly", I understand where you are coming from, but since this is part of a thesis I would like to have some evidence to back up the process.  Thanks for the advice on not exporting until after classification is done.  That makes a lot of sense actually considering the capacity of many systems.  So all the analysis has to be done "on the fly" right?  How about assessing accuracy and time constraints?

Do you have an email that I can send my abstract to?  I would like your input.  Again, I thank you for your time. 

Norman Nash

[CodyBenkelman]

Norman - re: histogram/color change after clipping, I am guessing that your clipped image has an automatic histogram stretch applied when added into the map.  If you go to table of contents --> properties of the clipped raster --> symbology, verify that the stretch is set to "NONE". 

If that doesn't solve the color change, please send a description and/or screen shots so we know what steps you are applying...  (alternatively, is it possible your original view has a stretch applied, so the color change you are observing in the clipped image is because it does not have the same stretch?)

Thanks

Cody B.