I have a question about geoprocessing tools and Mosaic Dataset. Can the Extract Multi Values to Points tool (or the like e.g., Sample etc.) be used to extract pixel values from a Mosaic Dataset comprised of individual raster images in a stack (monthly climate values) and across non-overlapping tiles (for example, 1x1 degree tiles)?
I’ve tried several different extraction tools but not matter what I do, the same cell value gets extracted for each point location. Further, the value that gets extracted is not contained in any of the raster images. My only suspicion for this later issue is that it’s calculating a summary statistic i.e., mean of the monthly values for the pixels that are coincident with the X, Y coordinate location.
I’m fairly new to using Mosaic Datasets so perhaps it’s merely operator error however; I would expect this to be a standard operation as I have already been performing this using points and individual images with this tool.
I would expect values to be obtained if everything is in the same coordinate system and single and multiband rasters are supported as per the help Extract Multi Values to Points—Help | ArcGIS for Desktop
I expected the same, a new column/field in the feature class for each raster image in the Mosaic Dataset e.g., ppt1, ppt2, ppt3 populated with the corresponding value from the Mosaic Dataset however; in my experience, expectations are usually much different than reality. I could go through and create a new column for each ppt value or, just load each individual ppt image into the tool but, that sorta defeats the purpose of using the Mosaic Dataset. Any ideas?
did you confirm the 'extent' in the Environments tab for the tool? I am wondering if the extent isn't being set properly, limiting the bounds of what is being examined.
To underline what Dan said, are you sure your sampling points are in the same coordinates system as the mosaic?
Don't look in ArcMap. Use Catalog and check the data properties.
When you extract values from a mosaic dataset, you are normally looking at the default visualization of the mosaic dataset. You could add some simple Raster Chain Functions to extract each single band, add them to the TOC and use the layers in the Extract Multi Values to Points tools.
Yes that is an option but again, doesn't that defeat one of the purposes of Mosaic Dataset and Extract Multi Values to Points tool? What I don't want to have to do is identify the large volume of different 1x1 degree tiles to be used as an input over a particular area of interest rather, use the Mosaic Dataset tile boundaries help me determine which tiles intersect with my feature class or even, let it run with the entire Mosaic Dataset and wherever there are null values in the output, those columns can be removed. I suppose I see the utility of the Mosaic Dataset as a visualization and image catalog from which, geoprocessing functions can be applied to the true data values. I may need to simply go back and use the extract tool and a mass of individual raster images.
If you created a mosaic dataset where each band represent a date period and is composed by multiple non-overlapping tiles, it should work. Take for instance this example. I have a mosaic dataset that is composed by several bands. The first band contains the DTM and the second the DSM. If I add the mosaic twice to my data frame and visualize one using a raster function that extracts the first band, and the second extracting the second band:
This will enable me to use both layer in the Extract Multi Values to Points:
... and will extract the values for both band, since they are in my TOC as virtual rasters:
Below the points taken over the different footprints (different tiles) of each band: