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I am new to GIS application and had just started working with Geotiff files.

Background:

Currently, I am provided with big Geotiff files around 200 MB - 500 MB each as raw data from my vendors.

Are JPEG-IN-TIFF files the same as the full Geotiff files but with the RGB image compressed?

  • Generally the policy is one question per question. On point 5, I think you misunderstand what GDAL_Merge does, it merges images not the component files. GeoTIFF stores the geolocation internally and does not need a separate tfw file, the prj file is always needed (unless converted to an aux file). If you're serving as a tileset that should contain the pyramids, so on point 4 GDALAddO does nothing useful for you - it's only for looking at individual tiles. If you have an RGBA raster I would discourage you from using JPEG compression, use DEFLATE instead with a high predictor. – Michael Stimson May 15 '18 at 5:06
  • When you serve the images you're only serving the bit that is on screen so the size of the source images does not matter, the size is based on your serving protocol and how you control that depends on your server software.. mucking around with the source images is unlikely to change the physical size of the image served no matter what colour space you put them in. If you have plenty of space on your server you need to balance storing the images uncompressed as decompression uses CPU and HDD access for the larger file size, this is what overviews are good for. – Michael Stimson May 15 '18 at 5:09
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This document https://www.awaresystems.be/imaging/tiff/specification/TIFFTechNote2.html gives comprehensive details about JPEG-in-TIFF. GDAL is using that revised version through the libtiff library.

For most GDAL user it is enough to know that the compression method that is applied to the image data does not affect the tags (except the compression method tag). The GeoTIFF tags remain the same and so also the georeferencing of the image. It is also good to know that JPEG data must be read totally before it can be decompressed and therefore it is important to use JPEG compression together with internal tiling when image size is big.

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