Define Overviews (Data Management)
Summary
Defines the tiling schema and properties of the preprocessed raster datasets that will cover part or all of a mosaic dataset at varying resolutions.
Usage
-
This tool is used when there are specific parameters you need to set to generate your overviews, such as
- Defining the location to write the files
- Defining an extent that varies from the boundary
- Defining the properties of the overview images, such as the resampling or compression methods
- Defining the overview sampling factor
-
Use the Build Overviews tool to generate the overviews after they've been defined with this tool.
You can use a polygon feature class to define the shape of the overview. An overview image will be created for every polygon in the feature class. Ideally, your feature class will be used to create one overview image. If you do not wish to use all the polygons in the feature class you can make a selection on the layer in the table of contents or use a tool such as Make Feature Layer to create a temporary layer representing only the desired polygons.
The default tile size is 128 by 128. The tile size can be changed in the Environment Settings.
This tool can take a long time to run if the boundary contains a large number of vertices.
Syntax
| Parameter | Explanation | Data Type |
in_mosaic_dataset |
The path and name of the mosaic dataset. | Mosaic Layer |
overview_image_folder (Optional) |
The folder or geodatabase where the overviews will be stored. Overviews that are stored and managed within personal and file geodatabases have the default overview folder location in the same workspace as the residing geodatabase. | Workspace |
in_template_dataset (Optional) |
A raster dataset or polygon feature class used to define the extent or shape of the overview. The extent of the raster dataset will be used when using a raster dataset. The shape of the polygon will be used when using a feature class. | Raster Layer; Feature Layer |
extent (Optional) |
Four coordinates defining the extent of the overview that will be generated. This is specified as space delimited in the following order: X-minimum X-maximum Y-minimum Y-maximum. The mosaic dataset boundary will be used to determine the extent of the overviews if an extent is not defined. | Envelope |
pixel_size (Optional) |
Base pixel size used to generate the overviews. The default is determined by the software. The units for this parameter is in the same units as the spatial reference of the mosaic dataset. | Double |
number_of_levels (Optional) |
The number of overview levels that will be generated. For a number greater than 0, it will be the number of overview levels generated. For example, 3 will generate three levels of overviews. If the value is left blank or -1, then an optimal number of overviews will be generated by the system. | Long |
tile_rows (Optional) |
Optimum number of rows in the overview. The larger the value, the bigger the file, and the more likely it will need to be regenerated if any lower image changes. This number can affect the number of overview images created. If it's a large number, then fewer overviews will be generated. If it's a small number, then more files are generated. | Long |
tile_cols (Optional) |
Optimum number of columns in the overview. The larger the value, the bigger the file, and the more likely it will need to be regenerated if any lower image changes. This number can affect the number of overview images created. If it's a large number, then fewer overviews will be generated. If it's a small number, then more files are generated. | Long |
overview_factor (Optional) |
The ratio used to determine the size of the next overview. For example, if the cell size of the first level is x, and the overview factor is 3, then the next overview pixel size will be 3x. | Long |
force_overview_tiles (Optional) |
Affects the levels at which overviews will be generated.
| Boolean |
resampling_method (Optional) |
The resampling algorithm used when creating the overviews.
| String |
compression_method (Optional) |
This defines the type of data compression that will be used to store the overview images.
| String |
compression_quality (Optional) |
Quality of the compression used with the JPEG compression method. The compression quality can range from 1 to 100. A higher number means better image quality but less compression. | Long |
Code Sample
This is a Python sample for DefineOverviews.
import arcpy
arcpy.DefineOverviews_management("c:/workspace/fgdb.gdb/md01",
"c:/temp", "#", "#", "30", "6", "4000",
"4000", "2", "CUBIC", "JPEG", "50")
This is a Python script sample for DefineOverviews.
#Define Overviews to the default location
#Define Overviews for all levels - ignore the primary Raster pyramid
#Define Overviews compression and resampling method
import arcpy
arcpy.env.workspace = "C:/Workspace"
arcpy.DefineOverviews_management("DefineOVR.gdb/md", "#", "#", "#", "#",
"#", "#", "#", "#", "FORCE_OVERVIEW_TILES",
"BILINEAR", "JPEG", "50")