topic Mosaic Dataset is solid Greay?? in Data Management Questions

Mosaic Dataset is solid Greay??

MikeBly — Wed, 21 Nov 2012 15:22:12 GMT

Hi,

I have 51 .asc files that i am trying to mosaic into one mosaic dataset. I first tried this with four of the tiles and it worked great. So I attempted to add all the others. The results were one big grey dataset. I then decided to try again with fewer tiles as a test and build pyramids and calculate statistics. This worked great, again add all the other rasters, same process, bad result, big grey dataset.

Since this I have not been able to even mosaic two files together, nothing but grey. I have tried also converting to .tif, and same results here. My end goal is a mosaic dataset that I can convert to one raster.

Any thoughts on what it going wrong in this process?

Thanks,

Mike

Re: Mosaic Dataset is solid Greay??

MathewCoyle — Wed, 21 Nov 2012 15:28:16 GMT

You should be able to accomplish your end goal directly by creating a raster dataset and then using the mosaic tool to add your original rasters without having to go through a mosaic dataset.

Your issue of all grey sounds like statistics are not being calculated for the overviews to display properly. Can you zoom in to pixel resolution and see if you see something different? If you have rebuilt and recalculated your statistics for your mosaic and your source data, try rebuilding your overviews.

Re: Mosaic Dataset is solid Greay??

MikeBly — Wed, 21 Nov 2012 19:11:03 GMT

Thanks for the reply. I have tried the method of creating a raster dataset as recommended. Everything appears to work properly, creating, loading, building pyramids and calculating the statistics. However, it appears that there is nothing there, nothing displays or previews in catalog and when I bring the dataset into arcmap, nothing is drawn.

I am unsure what you mean by rebuilding overviews, and how to go about this. Could you briefly explain? With the mosaic dataset and the "grey" issue, when I zoom right in I cannot distinguish between pixels, there are no values, despite calculating the stats.

Thanks,

Mike

Re: Mosaic Dataset is solid Greay??

MathewCoyle — Wed, 21 Nov 2012 19:24:16 GMT

Can you extract the pixel values from the mosaic dataset or is it just no data? Do your statistics have the distribution you would expect? Is the uncompressed size in GB of your mosaic dataset what you would expect? What is your pixel type, depth, no data values etc?

Re: Mosaic Dataset is solid Greay??

MikeBly — Wed, 21 Nov 2012 19:37:49 GMT

So, I can pull out pixel values, and the values i see are what I would expect. The depth is 32bit, type is floating point and the NoDataValue is null, there are no values for non data.

Also when I create this mosaic, despite the greying out, it only loads ~ half of the tiles I enter. This may be a memory issue, unsure. Interesting to note that I can still create a hillshade of course because the pixel values are still there.

Confused,

Mike

Re: Mosaic Dataset is solid Greay??

MathewCoyle — Wed, 21 Nov 2012 20:31:44 GMT

The grey generally means statistics are not calculated for you to display. I'd imagine some error occurred where the overviews or pyramids were created before the statistics were completed. Try starting over. Calculate statistics and build pyramids for your source rasters. Create a new mosaic dataset and import all your source rasters.

What version of ArcGIS and service pack are you using?

Re: Mosaic Dataset is solid Greay??

MikeBly — Thu, 22 Nov 2012 16:53:45 GMT

I am running 10.1 with no SP yet, SP is available, have not tried installing yet though. I will perform the calculate stats and build pyramids on the source and see what result i get.

Thanks again,

Mike

Re: Mosaic Dataset is solid Greay??

JeffreySwain — Mon, 26 Nov 2012 18:31:46 GMT

Also be sure to check the symbology of the raster in the mosaic dataset. If it is grey and you see the standard deviation stretch as None, then you will need the statistics. If it is grey and you have statistics, then apply a stretch. If the rasters are still grey then be sure that you have access to the data. By default, if the raster is not available a Constant Function will be appllied and the missing overview or raster will be grey.