Raster Mosaic, huge output file

[JustinReid]

Hi everyone,
I'm currently creating a mosaic of 5 images, between 30-60mb each. The resulting mosaic is a whopping 2gb.
I've tried tif, jpg and .jp2 but nothing seems to reduce the file size significantly.

I'm using "Mosaic to new raster" as I simply require one image to forward on to someone else.

Does anyone have any suggestions for this please?

Thanks 🙂

[chriss_]

Hi!
I guess the problem is that your rasters do not line up exactly. Therefore they are resampled to smaler rasterpoints. you do this 5 times and your file gets really big.  When running the mosaic tool you can change the "Mosaicking tolerance" what this does it moves your rasterpixel instead of resampling. Go to ArcgisHelp and search for "Mosaic (Data Management)" and look for mosaicking_tolerance.

[TimothyHales]

What format are the input images?  If it is a highly compressed format, then the rasters are being uncompressed through processing and the output format does not have the same quality of compression.

[GordonSumerling]

Hi,

it sounds like you are taking a jp2, jpg, ECW or MrSid file and moasicing them to a new image format but not specifying the Compression value in the environment varaiables. Before you output the raster select the Environments button, then select Raster Storage. Finally the Compression setting. Here I would suggest you pick JPEG2000 and set the compression at 75%. This will proabably give you a mosaic of comparable size to your original images combined.

If you are only going to use it in ArcMAP then you will get even more size reduction if you use the new Geodatabase format Mosaic Dataset. This leaves the images in their native format but builds pyramids (overviews) over the top of all 5 of you images. You could call it a pseudo mosaic as no new image is created but they are all displayed together as if they were mosaiced.

HTH

Gordon