Hi all,

In Arc 9.x there was a shortest path tool in the Spatial Analyst toolbar which i had used previously to determine the path taken from a point to the sea. Essentially, this would give an indication as to where a pollutant would enter the river network, based on the DTM (and flow direction).

Does anyone know id there is there an equivalent to this tool hidden somewhere in Arc 10?

Many thanks,

Claire

In Arc 9.x there was a shortest path tool in the Spatial Analyst toolbar which i had used previously to determine the path taken from a point to the sea. Essentially, this would give an indication as to where a pollutant would enter the river network, based on the DTM (and flow direction).

Does anyone know id there is there an equivalent to this tool hidden somewhere in Arc 10?

Many thanks,

Claire

You may have noticed by now that the limited set of functionality previously available on the Spatial Analyst toolbar is removed in ArcGIS 10. The full functionality of Spatial Analyst has always been in ArcToolbox > Spatial Analyst Tools. The tool you are looking for is called Cost Path located in the Distance toolset.

Cost Path can be used to derive the path of least resistance down a digital elevation model (DEM). In this case, use the DEM for the Input cost distance raster and the output from the Flow Direction tool for the Input cost backlink raster.

For those having problems using the interactive Steepest Path tool, I would suggest filling your DEM. I think you may have sinks and that could be why the path created is so short. Alternatively, use the Cost Path tool to do your analysis.

Best Regards,

Eric

When using the Cost Path tool to derive the path of least resistance, its my understanding that it requires two input points, A and B. It then traces the shortest path from point A to point B.

However in Arc 9.x the shortest path tool only required one input point, A, and it then traced the shortest path from point A to the edge of the DEM, which effectively becomes point B.

Therefore the shortest path tool and cost path tool are slightly different. I have a similar problem to Claire as regards tracing a surface water run-off path into the river/sea and it would be great if you could advise of a similar tool in Arc 10.

Kind regards,

Tony

I am sorry for going off topic, but I just have to ask/make this remark:

As it is not bad enough that some functions have been moved to other locations (why? the functions did't change) causing users to have to spend a lot of time looking for the right functions when giong to version 10: Why change the name too?

The names used for functions in spatial analysist are already debatable in version 9, but 'cost path'? Try to imagine being a new user, trying to find a function that can help him or her to determine the flow path on a DEM. Do you think that person will ever think that 'cost path' will do that when the user sees the function in the toolbox? Or better: Do you think a person would ever type 'cost path' in the search engine when looking for this functionality?

I was hoping that version 10 would be a fast improvement on the user friendliness of the software, because that is the area in which the biggest (and easiest) improvements can be made as far as I'm concerned.

I hope you forgive my of topic response.

Hi Tony,

The Shortest Path tool and the Cost Path GP tool are the same tool with different names. I don't have 9.x installed to take the screenshots necessary to highlight this so I'll just point you to some documentation.

Under Analysis Concepts > Distance Analysis > Least Cost Path and Least Cost Corridor you'll find generic information regarding what cost path/corridor analysis is and how to perform it in ArcGIS. On this page you will find instructions (Links) to Learn how to calculate least cost path using the Spatial Analyst toolbar and to Learn how to calculate least cost path using the Cost Path tool

In the Usage Tips section (for the GP tool documentation) it states the following:

"Cost Path can also be used to derive the path of least resistance down a digital elevation model (DEM). In this case, the DEM will be the input cost distance raster and the flow direction raster will be the input cost backlink raster. Valid flow direction raster values are 1, 2, 4, 8, 16, 32, 64, and 128; valid values in the backlink raster are 1, 2, 3, 4, 5, 6, 7, and 8. Both of these rasters are acceptable."

Attached are screenshots of a simple model I made and the results overlaid on a hillshade to give you some perspective.

## Attachments

I'm trying to perform a similar operation with a simple raster of water table elevation I created from well data. In your attachment, you have three inputs for the Cost Path tool. I have two: the WT elevation raster and the output flow direction raster derived from the Flow Direction tool.

What I don't quite understand is what my input equivalent to your "Raindrops" input should be. The Cost Path tool requires it to be a raster, but it appears to me that your input -- several raindrops -- is a point layer. Can you clear this up for me? Clearly my knowledge of raster processing is sorely lacking.

Thanks,

Paul

Many raster tools accept features as well as rasters and convert on the fly (using default raster properties). You can control this on-the-fly rasterizing (cell size etc) using the raster geoprocessing environment.

I would like to calculate distence between a point on the river and river spring. Does anybody know any tool to do that? Or maybe a tool which can find the longest path from a point on the river to river spring?

TNX

Blaž

My recollection is that there was a big difference between the SA toolbar-based "shortest path" option and the "cost path" tool: what they produce. The old "shortest path" tool generated a set of graphical vectors that could be saved as a shapefile to produce good-looking graphics by manipulating line thickness etc. Cost Path only generates a raster output, which is extremely hard to display in an attractive way. "Lines" are too thin (restricted to the input direction raster resolution) and because of the planar topology, the cost path tool can't generate distinguishable lines when paths to different destinations coincide. Thus if you want, as I'd like to, to subsequently select only paths with a length less than a certain value, it can't be done.

I've been trying to find a workaround for the removed "shortest path" capability, but have had no luck yet. So it probably means I'll be installing Arc9 (again). Sorry to bring up an old topic, but I'd really, really like to find a way to get vector, instead of raster, output for least-cost paths. I'd hoped this capability would be back in Arc10.1, but it appears to have fallen off the table.

Least-cost Paths are fundamentally lines and it would be great to have them returned that way!

-John