topic Re: Extract Multi Values to Points and Mosaic Dataset in Geoprocessing Questions

Extract Multi Values to Points and Mosaic Dataset

ChuckWerstak1 — Tue, 05 Jul 2016 23:08:55 GMT

Hi everyone,

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.

Thanks,

Chuck

Re: Extract Multi Values to Points and Mosaic Dataset

DanPatterson_Retired — Tue, 05 Jul 2016 23:29:19 GMT

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

Re: Extract Multi Values to Points and Mosaic Dataset

ChuckWerstak1 — Tue, 05 Jul 2016 23:35:38 GMT

Hi Dan,

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?

Thanks,

Chuck

Re: Extract Multi Values to Points and Mosaic Dataset

DanPatterson_Retired — Wed, 06 Jul 2016 00:15:55 GMT

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.

Re: Extract Multi Values to Points and Mosaic Dataset

ChuckWerstak1 — Wed, 06 Jul 2016 02:17:39 GMT

Hi Dan,

Yes I did but, that didn't fix the issue.

Re: Extract Multi Values to Points and Mosaic Dataset

NeilAyres — Wed, 06 Jul 2016 05:45:58 GMT

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.

Re: Extract Multi Values to Points and Mosaic Dataset

XanderBakker — Wed, 06 Jul 2016 12:20:19 GMT

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.

See: Extract Band function—Help | ArcGIS for Desktop

Re: Extract Multi Values to Points and Mosaic Dataset

ChuckWerstak1 — Wed, 06 Jul 2016 14:05:35 GMT

Hi Neal,

Yes, all of the images and the feature class are in the same coordinate system. I'll keep looking...

Thanks,

Chuck

Re: Extract Multi Values to Points and Mosaic Dataset

ChuckWerstak1 — Wed, 06 Jul 2016 14:13:08 GMT

Hi Xander,

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.

Thanks,

Chuck

Re: Extract Multi Values to Points and Mosaic Dataset

XanderBakker — Wed, 06 Jul 2016 16:33:31 GMT

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:

Re: Extract Multi Values to Points and Mosaic Dataset

ChuckWerstak1 — Wed, 06 Jul 2016 17:41:06 GMT

Hi Xander,

I see how this can work but, I'm having trouble setting it up. Could you please show the steps used to "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:"

Just to be clear on my raster images here's what I have:

Tile "X1" (12 individual images-1 image per month)

Tile "X2" (12 individual images-1 image per month)

Tile "X3" (12 individual images-1 image per month)

The monthly images within each "X" tile have the exact same extent (a time series).

Thanks,

Chuck

Re: Extract Multi Values to Points and Mosaic Dataset

DanPatterson_Retired — Wed, 06 Jul 2016 17:52:32 GMT

Chuck... I am just curious, what is it you are trying to do with the data? Just view it or do you intend to do some analysis/summary with it?

The only reason I ask, is when I see 'multi-anything' and it isn't some spectral band reference to remote sensing and imagery, I wonder what people are doing with their data. I also wonder if people know about the other tools available to work with multidimensional raster/array data that contains interval/ratio scale data. This question also surfaces when I see people extracting values to points, I wonder what the purpose of the extra step is from an analytical point of view. In other words, why are they extracting to points, if they intend to 'do something' with the points and if so, what is it they are using the point data structure for.

Re: Extract Multi Values to Points and Mosaic Dataset

ChuckWerstak1 — Wed, 06 Jul 2016 18:27:07 GMT

Hi Dan,

This is in fact an RS driven study. I am building tree species distribution models in an ensemble classifier using a substantial amount predictor data e.g., Landsat imagery (raw, indices, transformations in a time series), topographic derivatives, climate data, soils data, etc. and, reference data (plot data). Extracting the values from the predictor data for all of the reference data is just the first step in the study. Since I have so many climate image tiles, utilizing mosaic datasets seems to be the most efficient way to manage and build the preliminary datasets for analysis.

I will look into converting the rasters to NetCDF format and determine if that could be useful in the analysis.

Thanks for the tip,

Chuck

Re: Extract Multi Values to Points and Mosaic Dataset

DanPatterson_Retired — Wed, 06 Jul 2016 18:43:12 GMT

Ok... thanks... don't forget the numpy and scipy stacks as well and they only need numpy arrays (*.npy for single or *.npz for stacked) and may be a simpler data structure if most the array contents aren't temporal.

Re: Extract Multi Values to Points and Mosaic Dataset

XanderBakker — Wed, 06 Jul 2016 18:55:47 GMT

Hi Chuck Werstak ,

What I would probably do (if I didn't have a mosaic dataset) would be to create a band for each month and that would result in a mosaic with 12 bands. So for each tile you would use the composite bands tool to create a raster with 12 bands and load these rasters in a mosaic dataset that you configured to have 12 bands of the proper cell type.

Now that you have a mosaic dataset, you could have (or create) an additional field in the Footprints with the value of the month. This can be used in the query definition to filter a specific month. That should work too.

Edit: I have created mosaic dataset with multi-temporal data, and specified for each raster in an additional field in the footprints featureclass, the start and end date of the raster. This enables the visualization through time of the data when you time-enable the layer.

Re: Extract Multi Values to Points and Mosaic Dataset

ChuckWerstak1 — Wed, 06 Jul 2016 18:58:24 GMT

Hi Xander,

I think I was able to replicate what you did. The difference between the images you ginned up and mine are that you seem to have created an image stack from two different coincident images (tiles) whereas mine are separate images.

Would there be a way do the same thing less creating the image stack? That would help tremendously!

Thanks,

Chuck

Re: Extract Multi Values to Points and Mosaic Dataset

XanderBakker — Wed, 06 Jul 2016 19:04:19 GMT

Is it possible to share the content of the Footprints (a screenshot)?

For instance in the sample below:

... each raster represents a date. The mosaic only contains a single band and each raster contains the same extent. I added two additional fields contains start- and end date for each raster.

Re: Extract Multi Values to Points and Mosaic Dataset

ChuckWerstak1 — Wed, 06 Jul 2016 21:53:59 GMT

Hi Xander,

Here's the screen grab of the mosaic dataset attribute table.

I still can't seem to get this to work with individual image files loaded into the mosaic dataset. I can get it to work if I layer stack the images into one multi-band image.

Thanks,

Chuck

Re: Extract Multi Values to Points and Mosaic Dataset

XanderBakker — Wed, 06 Jul 2016 22:01:05 GMT

I assume that this is a screenshot of a test mosaic with 4 rasters:

n42w111ppt1

n42w111ppt2

n42w111ppt3

n42w111ppt4

... and 3 overviews. I see you created a field with the value of the month.

Could you provide a screenshot of the one that you created with all the rasters multiple tiles and all 12 months?

Re: Extract Multi Values to Points and Mosaic Dataset

ChuckWerstak1 — Wed, 06 Jul 2016 22:36:42 GMT

Xander,

Here's an example with 24 rasters in a mosaic dataset. I will eventually have thousands...