Mosaic Error
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Mosaic Error
By RHehre in ERDAS Software Forum
Hello!
I am trying to mosaic a small number of image files, but keep encountering the error ~ file size will exceed .tif limit of 4GB. The thing is, my file size is nowhere near 4GB? To complicate matters, when I try running a larger number of files it works just fine (although it takes all day). Any suggestions?
-Rachel
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Re: Mosaic Error
By Jarlath O'Neil-Dunne in ERDAS Software Forum
A simple solution might be to specify the output as .img then convert to .tif after the mosaic.
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By RHehre in ERDAS Software Forum
I feel like I may have tried, this - but I'll give it a whirl! Thanks!
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Re: Mosaic Error
By Donn Rodekohr in ERDAS Software Forum
Rachel,
Check the Preference settings for .tif files. Make sure that the compression setting is on PacBits or if your are licensed for LZW use that. I believe that the default is NONE which will result in humongous TIFFs.
I also believe that PacBits is the default Tiff setting for Photoshop output.
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Re: Mosaic Error
By RHehre in ERDAS Software Forum
Hi Donn,
My settings are for LZW compression. The issue seems to be unrelated to my actual file size, as the inputs are ~ 500MB-1GB, but I still get the error message: File will exceed the TIFF limit of 4GB. Please save to a different format. I'm wondering if there is some other issue that is triggering this error - maybe a directory is full or there isn't enough memory in some cache?
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Re: Mosaic Error
By Cheryl Brantley in ERDAS Software Forum
Hello Rhehre,
This is probably a dumb question, but have you calculated the actual full array of the file after mosaic? You probably already know you can't just add up the input file sizes unless there is no background. Are all the files the exact same size in columns and rows? And do they line up into perfect rectangles? It sounds like your inputs (500mg to 1GB) are different sizes. If that is the case you still have to account for the background pixels. They often take up a lot of your file size.
Cheryl
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Re: Mosaic Error
By RHehre in ERDAS Software Forum
Hi Cheryl,
Thanks for the suggestion. I am very new to ERDAS and image processing, so no, I have not calculated the full array. I am mosaicking georeferenced historical imagery for a number of years, so the file size varies between datasets (ie. 1992 single B&W image is ~140MB, for 1998 single RGB image ~450MB) I realize now of course what you are saying about the background values, is there an easy way to calculate this?
Thanks,
Rachel
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Re: Mosaic Error
By Cheryl Brantley in ERDAS Software Forum
Yes, You can Google it and find many textbook definitions for "how do I calculate output file size using raster data." Read these for a technical understanding.
Basically, assuming your the data is 8Bit, I usually do this:
Looking at your data, determine the largest total number of pixels across the project and and then the same for the height. The easiest place to find the numbers are ImageInfo from the viewer. If there are many images then you will need to add them up accross the project area. Don't think of data in terms of the land you see in the viewer; think of it in terms of the full image array which includes all those background areas. Take the longest row of pixels and the highest column of pixels for the entire project area and multiply them together. This gives you the output file size for one band of 8bit data. If your data is multiband, then you take your calculation and multiply it times the number of bands. For 8BIT data this gives you the file size in bytes. Convert the bytes to MG, GB or TB depending on how big it is... (one 8bit pixel = 1byte.)
If your data is not 8Bit data, or you change your output pixel size, or you change the projection then you will need to do additional calculations.