Transform - Tiles: Limit

The Limit template appears in the template list when a raster tile field, of type Tile, has been picked in the Transform pane.  The template computes bounds to upper and lower limits of ranges of values of a specific channel in a tile.

 

Limit

Limit values of a specific channel in a tile: 

 

  • limit both - limit values to a range between the minimum and maximum values specified.  

  • limit maximum - limit values to no greater than the maximum value specified.
  • limit minimum - limit values to no less than the minimum value specified.

 

Launch the template by choosing a Tile field and then double-clicking the Limit template.  When the template launches we can specify options.

 

 

Limit : limit both

Limit values to a range between the At least and At most values specified.    The operation works on the single channel chosen in the Channel parameter.

 

Take the source field, increase all pixel values lower than the At least value to the At least value, reduce all values greater than the At most value to the At most value, and leave all values equal to or in between the At least and At most values unchanged.   Place the result in the Result destination.

 

Another way to describe the effect is to consider the At least field the floor and the At most field the ceiling for what is taken from the Value field.

 

 

With the focus on the Elevation Raster image, in the Transform pane we choose the Tile field and then the Limit template.

  

 

In the Limit template we choose limit both as the Operation   We enter an At least value of 250 and an At most value of 300.

 

For the Result destination, we choose New Field and then enter Tile result as the name of the new tile field to add to the table.  For the new image name we enter Elevation result.   We could use whatever names we want for the names of the new tile and image, but it is wise to use names that remind us of what they are supposed to be.

 

Press Transform.  

 

A new image called Elevation result appears in the Project pane.   We drag and drop the new Elevation result image into the Elevation Raster window as a layer.  To style the new image the same as the original Elevation Raster image, we copy the StylePixel property from the Elevation Raster image to the Elevation result image.

 

Comparing the original image to the result:

 

 

The terrain height display becomes limited at the low end to the At least value of 250 and at the high end to the At most value of 300.  The result is to extract varying terrain elevations from Value that are between 250 and 300, and to replace all other values with 250 for heights that were below the At least value and with 300 for heights that were above the At most value.  

 

See the Know Your Limits video.

 

Limit : limit maximum

Limit values to no greater than the At most value specified.   The operation works on the single channel chosen in the Channel parameter.

 

Take the source field, reduce all values greater than the At most value to the At most value, and leave all values equal to or less than the At most value unchanged.   Place the result in the Result destination.

 

Another way to describe the effect is to consider the At most field the ceiling for what is taken from the Value field.

 

 

With the focus on the Elevation Raster image, in the Transform pane we choose the Tile field and then the Limit template.

 

 

Preview: Apply Limit High to Tile using an At most value of 300.

 

In the Limit template we choose limit maximum as the Operation   We enter an At most value of 300.

 

For the Result destination, we choose New Field and then enter Tile result as the name of the new tile field to add to the table.  For the new image name we enter Elevation result.   We could use whatever names we want for the names of the new tile and image, but it is wise to use names that remind us of what they are supposed to be.

 

Press Transform.  

 

A new image called Elevation result appears in the Project pane.   We drag and drop the new Elevation result image into the Elevation Raster window as a layer.  To style the new image the same as the original Elevation Raster image, we copy the StylePixel property from the Elevation Raster image to the Elevation result image.

 

Comparing the original image to the result:

 

 

The terrain height display becomes limited at the high end to the At most value of 300.  Terrain elevation values that were above 300 have now been set to the maximum limit of 300.  

 

See the Know Your Limits video.

 

Limit : limit minimum

Limit values to no less than the At least value specified.  The operation works on the single channel chosen in the Channel parameter.

 

Take the source field, increase all values less than the At least value to the At least value, and leave all values equal to or greater than the At least value unchanged.   Place the result in the Result destination.

 

Another way to describe the effect is to consider the At least field the floor for what is taken from the Value field.

 

 

With the focus on the Elevation Raster image, in the Transform pane we choose the Tile field and then the Limit template.

 

 

In the Limit template we choose limit minimum as the Operation   We enter an At least value of 300.

 

For the Result destination, we choose New Field and then enter Tile result as the name of the new tile field to add to the table.  For the new image name we enter Elevation result.   We could use whatever names we want for the names of the new tile and image, but it is wise to use names that remind us of what they are supposed to be.

 

Press Transform.  

 

A new image called Elevation result appears in the Project pane.   We drag and drop the new Elevation result image into the Elevation Raster window as a layer.  To style the new image the same as the original Elevation Raster image, we copy the StylePixel property from the Elevation Raster image to the Elevation result image.

 

Comparing the original image to the result:

 

 

The terrain height display becomes limited at the low end to the At least value of 300. Terrain elevation values that were below 300 have now been set to the mimimum limit of 300.  

 

See the Know Your Limits video.

 

 

Notes

Sample image - Many illustrations for transforms for raster images use an Elevation Raster sample image, a version of the formatted example of importing an SDTS format DEM from the Example: Import DDF SDTS DEM Raster File  topic.   The example project may be downloaded from the Downloads page on the Manifold web site.

 

Everything Math - For a handy reference to anything in mathematics, see the Wolfram MathWorld site.   Thank you, Wolfram!

 

See Also

Transform Pane

 

Transform Reference

 

Transform - Tiles