Latest Contributions by JerryHelfand1

I am not an expert in image processing using ArcGIS, but I suspect that if all one wants to do is view the imagery as a backdrop, the hardware you describe is likely OK.  However, if any kind of bulk processing is needed, then one has to look at the amount of information that needs to be handled in RAM at one time.  You mention that the space taken by the data is a bit over 200Gb.  That could be misleading.  For instance, if each image is a 512 by 512 tile, 3 band image, 8 bit pixel depth, uncompressed space needed would be somewhere higher than 10 Tb.   Again, I don't really know in detail how ArcGIS handles imagery, but this would be my main concern.  Hence, Michael Volz's recommendation to try doing what you want to do on a small sample is the wiser path to follow. I do have experience in simply displaying thousands of rasters that I imported into a mosaic dataset.   (I'm talking about 8 Tb).  But if I wanted to do any geoprocessing on the whole full resolution (say, raster to vector), my system froze, even though I have 32 Gb of RAM & 8 cores.  I have had to split the data into manageable subsets.  Of course, I could have been doing something wrong, but my work got done. ... View more

Dan, I read that document before posting.  See, if I follow the documentation as you suggest, then I would want to use non-atmospherically-corrected image for the Tasseled Cap function.  Maybe if I calculate NDWI and NDVI, the results might be OK but not optimal.  But if I want to do image classification (supervised or object-based) and compare results from different vintage of images, then it's required I use the atmospherically-corrected version.    As backup for my stance, the section on Atmospheric Correction in Imagery and GIS Best Practices for Extracting Information from Imagery  (by Green, Congalton & Tukman, ESRI Press 2017 pp 153-156) supports this, and also mentions that "availability of [atmospheric absorption data from specific bands within the image],.... has sparked a resurgence of algorithm development to produce better absolute atmospheric correction methods." (p155).  What is not clear is whether the latest capabilities have been programmed into ArcGIS/Pro. So, might you or anyone have a link to an document that describes the exact parameters used (the formula) in ArcGIS Pro or ArcGIS 10.5, and the methodology followed to derive them?  The existing documentation is still a bit of a black box, and doesn't seem to have been updated other than adding newer sensor names.  For the public health project I'm supporting on a volunteer (zero pay) basis, this is far less than ideal.  For now, until I get or find more definitive information, I must ignore the Tasseled Cap function because it may give varying results from image collected on different dates because the reflectance will vary along with variations in atmospheric moisture content.    ... View more