PPTABLE

Description

Finds all the pour points between watersheds (a table of linkages for watersheds) and stores them in a table. Pour points are the points of lowest elevation on the common boundary between watersheds.

Parameters

Name	Type	Length	Value range
InputFDEP: Input fill depression channel*	Raster port	1 - 1
InputDBIC: Input watershed results channel*	Raster port	1 - 1
Port Settings: Resample mode*	Raster port	1 - 1024	Nearest | Bilinear | Cubic Default: Nearest
Report	String	0 - 192	See parameter description

* Required parameter

Parameter descriptions

InputFDEP: Input fill depression channel

Specifies the input channel that contains the filled depression data.

InputDBIC: Input watershed results channel

Specifies the input channel that contains the watershed results. This channel is obtained by running the WTRSHED function. The input channel must be 16-bit signed integer or 32-bit real.

Port Settings: Resample mode

Specifies the type of image resampling desired.

Report

Specifies where to direct the generated report.

Available options are:

• LOG: generates a report on the terminal (default)
• <modulename.RPT>: appends a report to the module's RPT file
• DISK: generates a report on file "IMPRPT.LST"

Details

PPTABLE finds all the pour points between watersheds (a table of linkages for watersheds) and stores them in a table. Pour points are the points of lowest elevation on the common boundary in between watersheds.

To use OVERLND, you must first run the DWCON function.

For more information about the drainage network functions, see the help for DWCON.

PPTABLE prints out, in tabular form, the pour points of all watersheds. A watershed links to another at a pour point, the point of lowest elevation on the common boundary between the two watersheds. If a watershed were to be filled with water, this minimum elevation is where the water would "pour" into its neighbor. To accommodate data sets with internal (or closed) drainage, or where two or more pour points leading to different watersheds are very close or equal in elevation, all possible pour points are computed. PPTABLE uses the filled depression channel and the watershed results to produce a pour point table. For each watershed, all bordering watersheds are examined, including the watersheds with a label of zero indicating that they flow to the data set edge, and a pour point is found on each watershed-to-watershed border. The line and pixel coordinates and elevation of each pour point are recorded in the table.

Areas that are not well drained will exhibit multiple pour points of the same elevation, while well-drained areas will rarely exhibit this feature.

The pour point table results can be transferred to a relational database management system where the linkages can be used to aggregate watersheds. The line and sample coordinates of the pour point can also be transferred to a vector-based spatial analysis system as point data sets for additional analysis and plotting.

FDEP (InputFDEP) specifies the filled depression channel, which is obtained by running the DWCON function.

DBIC (Input DBIC) specifies the channel of that contains the watershed results, which is obtained by running the WTRSHED function.

References

Jenson, S.K. and Domingue, J.O. "Extracting Topographic Structure from Digital Elevation Data for Geographic Information System Analysis". Photogrammetric Engineering and Remote Sensing, Vol. 54, No. 11, November 1988, pp. 1593-1600.