Frequently asked questions

Find answers to common questions about voxel layers.

What type of volumes are supported?

  • The voxel volume must be a regularly gridded volume with a specific dimensional order—x,y,z,t or t,z,y,x.
  • An irregularly gridded voxel can be consumed as point features and interpolated with the Empirical Bayesian Kriging 3D and GA Layer 3D To NetCDF tools.

The Add Multidimensional Voxel Layer dialog box does not recognize my NetCDF file. Why?

Unsupported NetCDF files do not display variable information on the Add Multidimensional Voxel Layer dialog box and cannot be added to a local scene. A warning button Warning appears on the dialog box. Click it to see a report on any issues with the NetCDF file. Ensure that the NetCDF file is volumetric and contains the necessary x,y,z dimensions with recognized coordinate variable naming. See supported voxel formats for more information. The Python NetCDF4 library or ArcPy NetCDFFileProperties class can validate dimension and variable information for a NetCDF file.

Which coordinate systems do voxel layers support?

Voxel layers support both geographic and projected coordinate systems in a local scene. Ellipsoidal and gravity-based vertical coordinate systems are also supported.

How are coordinate systems read from a NetCDF file?

Coordinate variables in a NetCDF file determine which variables represent the x,y,z information. The coordinate system of the data created from a NetCDF variable is determined by the units of the coordinate variables and whether the grid_mapping attribute exists.

If the units of the coordinate variables specified as the x- and y-dimensions are the units of longitude and latitude, respectively, the data is in a geographic coordinate system (GCS) and is automatically set as WGS 1984.

If the standard_name of the coordinate variables specified as the x- and y-dimensions are projection_x_coordinate and projection_y_coordinate, respectively, and the variable has a grid_mapping attribute, the data is in a projected coordinate system (PCS). The projection name, type, and other parameters are defined by a grid_mapping variable.

NetCDF files created from geoprocessing tools in ArcGIS AllSource contain a global attribute esri_pe_string. The voxel layer reads the well-known text (WKT) from this global attribute to set the coordinate system.

My NetCDF file has the wrong coordinate system. What should I do?

Place a projection file (.prj) with the same name as the NetCDF file in the same directory to override the coordinate system of the NetCDF file. See Save a coordinate system as a projection file to learn how to create a projection file.

I've received a notification that my voxel layer will not draw.

Both the horizontal and vertical coordinate systems of the voxel layer must match the scene's coordinate system. Open the scene properties to confirm both the horizontal and vertical coordinate systems are set properly.

How do I repair a broken voxel layer?

To repair a voxel layer, click the red exclamation point in the Contents pane. The NetCDF file used to repair the broken layer must be the same NetCDF file that was used to create the original voxel layer. If the NetCDF files do not match, an error message appears.

How do I share a voxel layer?

Voxel layers are supported in ArcGIS AllSource as well as ArcGIS Enterprise and ArcGIS Online. You can create a voxel scene layer package with the Create Voxel Scene Layer Content tool and upload and publish the package as a web scene layer.

Can I add multiple voxel layers to my local scene?

Yes. Ensure that the voxel layers do not overlap in the same area, as only one voxel layer displays at a time. Also ensure that your graphics card can handle displaying multiple voxel layers. It is recommended that you have at least 4 GB of dedicated graphics memory. See ArcGIS AllSource system requirements for more information.

How do voxel layers support time?

Voxel layers support NetCDF files with x,y,t or x,y,z,t dimensions. The time variable must have a units attribute and the time values must be sorted in ascending order. The following formats are supported: YYYY:MM:DD, hh:mm:ss, YYYY:MM:DD, and YYYY:MM:DD hh:mm:ss hh:mm, where the last hh:mm is a time zone. Use the Python NetCDF4 library if the time values need to be sorted in ascending order.

What is the .vxc1 file that is created next to my NetCDF file?

The .vxc1 file is created anytime a user adds a voxel layer to a local scene with the Optimize for performance option enabled. This file can be used by any ArcGIS AllSource application that is displaying the NetCDF file as a voxel layer. The .vxc1 file increases in size as a user displays more variables and creates more isosurfaces and sections. Disable this functionality by unchecking Optimize for performance on the Display page of the voxel layer properties. The .vxc1 file can be manually deleted in the file system.

Why are all volumes in the NetCDF file not shown?

Only one volume of the multidimensional data can be visualized. The volume with the highest number of variables is set. If the number of variables is identical, the volume is prioritized by dimension. For example, the x,y,z,t variables are chosen over x,y,z and x,y,z variables are chosen over x,y,t variables. To visualize multidimensional volumetric data as a voxel layer, it is recommended that you have only one volume defined.

Why are voxel scene layers with discrete variables not drawing in ArcGIS AllSource 3.0?

Starting at ArcGIS AllSource the experience of working with discrete voxel variables has been simplified. ArcGIS AllSource casts the original data values, and depending on how the data are stored in the NetCDF file, the casting of discrete values may differ. For example, signed integers or floating point formats will be represented as a signed byte where unsigned integers will be represented as an unsigned byte.

The values that have been cast are shown in symbology and pop-ups. If your data is outside of the range of a signed or unsigned byte, or if the casting of values is causing conflicts, you can remap the values via Python script.

A voxel scene layer (SLPK or service) created prior to ArcGIS AllSource 3.0 will not draw discrete variables. You must run the Create Voxel Scene Layer Content tool to recreate the SLPK or republish the voxel scene layer service.

How do voxel layers support automatic labels on unique values?

If you use the Nearest Neighbor 3D geoprocessing tool, the output NetCDF contains labels that a voxel layer honors. Alternatively, use Python to create the NetCDF file or alter the NetCDF file to include esri_unique_values and esri_unique_labels attributes for the visualized variable.

An example to specify labels for two unique values for a variable in a NetCDF file.

 :esri_unique_labels = "Above", "Below";
 :esri_unique_values = 1, 0; // int

What is a regularly gridded voxel dataset?

A voxel dataset is regularly gridded if the spacing between values is constant. For example, z-values are irregular if the spacing changes across the z-range, such as 0, 5, 50, 100. Values are regular if they are spaced at constant intervals such as 0, 5, 10, 15, 20.

How do I fix data that is irregular?

You can use the regularize Z Python script or toolbox tool to adjust the spacing in the voxel dataset.

Can I automate creating voxel layers?

Yes, you can use the Make Multidimensional Voxel Layer tool to create a voxel layer. To share to ArcGIS Enterprise or ArcGIS Online, use the Create Voxel Scene Layer Content tool and Share Package tool.

Can I view the count for each voxel unique value?

Yes, you can view the count for each unique value in the Symbology pane.

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