This tool can be used to create a longitudinal profile plot. A longitudinal stream profile is a plot of elevation against downstream distance. Most long profiles use distance from channel head as the distance measure. This tool, however, uses the distance to the stream network outlet cell, or mouth, as the distance measure. The reason for this difference is that while for any one location within a stream network there is only ever one downstream outlet, there are usually many upstream channel heads. Thus plotted using the traditional downstream-distance method, the same point within a network will plot in many different long profile locations, whereas it will always plot on one unique location in the distance-to-mouth method. One consequence of this difference is that the long profile will be oriented from right-to-left rather than left-to-right, as would traditionally be the case.

The tool outputs an interactive SVG line graph embedded in an HTML document (`output_html_file`). The user must input a D8 pointer (flow direction) raster (d8_pointer), a streams raster image (`streams_raster`), and a digital elevation model (`dem`). Stream cells are designated in the streams image as all positive, nonzero values. Thus all non-stream or background grid cells are commonly assigned either zeros or NoData values. The pointer image is used to traverse the stream network and should only be created using the D8 algorithm (d8_pointer). The streams image should be derived using a flow accumulation based stream network extraction algorithm, also based on the D8 flow algorithm.

By default, the pointer raster is assumed to use the clockwise indexing method used by WhiteboxTools. If the pointer file contains ESRI flow direction values instead, set `esri_pointer=True`.

## See Also

long_profile_from_points, profile, d8_pointer

## Function Signature

`def long_profile(self, d8_pointer: Raster, streams_raster: Raster, dem: Raster, output_html_file: str, esri_pointer: bool = False) -> None: ...`

## Project Links

WbW Homepage User Manual Support WbW