Student Question regarding ASTER Orthorectification

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Last Post 06 Jul 2015 09:18 AM by anon

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anon

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06 Jul 2015 09:18 AM
Hey there, I'm a GIS/Remote Sensing student, writing my senior thesis on geothermal energy reconnaissance using ASTER imagery in Colorado. I'm fairly new to remote sensing, and most of the labs I've done used pre-processed and pre-orthorectified imagery, so I don't have a lot of practice with orthorectification. My data: I have ASTER L1B and L1T imagery, and I also have a point shapefile of oil/gas well locations with anomalous temperatures and UTM coordinates. I'm at a total loss as to how I can use the shapefile as my GCP for the ASTER imagery, and if that's possible, or if I should orthorectify using some other method. Also, do I have to play with datums/projections/coordinate systems for the ASTER imagery, and if so, how do I do this? I am more familiar with ArcGIS software than I am ENVI (we mostly used ENVI Classic in our labs in class), and I know I could likely fuse the two (ENVI and ArcMap point shapefiles) in my orthorectification workflow, but I really have no idea as to what the best methodology is. It's all much more complicated than what I learned in class! Can you help me orthorectify my imagery? Any help is much appreciated as my senior thesis is due in September :-) Blessings and thanks!

MariM

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06 Jul 2015 03:32 PM
I am assuming your ASTER '1T' is a terrain corrected product? ENVI does not allow you to use RPC Orthorectification with ASTER L1B data since it has already been projected. If you are wanting to perform an image-to-image registration between your ASTER 1B and 1T product, then you might give the Image Registration workflow a try in ENVI.

Deleted User

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07 Jul 2015 08:49 AM
MariM, Thank you, I will try the image registration workflow (I’m assuming you mean this? http://www.exelisvis.com/...ageRegistration.html ) By ASTER ‘1T’ I did mean the AST_L1T terrain corrected product. I was curious, though, if I could use the point shapefile in any way to pinpoint specific locations within the ASTER_L1B (or AST_L1T) image that I’d like to explore for anomalous thermal temperatures? The point shapefile is what I initially used to find areas in Colorado that showed geothermal energy potential. As they have UTM coordinates, can I use them with the ASTER imagery inside ENVI as GCPs, or simply marking them on the image, for example? I’d just like to specifically explore these locations in different TIR bandwidths, and then conduct some bandmath algorithms I have from a paper I’m using to see if the temperatures present at those sites confirm the well temperatures from the point shapefile. Apologies for my lack of clarity in describing this stuff. The vocab is new :-)

MariM

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07 Jul 2015 10:51 AM
You should be able to open the Shapefile directly in ENVI 5.2 and overlay the shapefile on either the 1T or 1B dataset. It might be a good way to determine if the 1B dataset is accurately georeferenced if you compare it to the 1T dataset. There isn't a good way to import the points from the shapefile as GCPs or tie points but you can use your cursor to find the location where the point lies in the image and enter this location as a GCP/tie point. It will take a little trial and error to see how that might work for you.

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