You wish to generate 25 random sites for a specific catchment, then compute their relative position.



Processing Task


You have prepared your river network and added the required attribution to the network so you can use the Extract positional information for site.  How do you know which attributes you need to add to the network so this tool will function? The answer is in the help file, under the usage section.


You could have run each tool separately but in this example a model was built which would allow you to run the logic multiple times.

The logic of this model is to select the polylines for a specific catchment, the selection is fed into the sampling tool and 25 random sites are created using the selected network. These sites are fed into the Extract positional information tool to create the output table positionaldata.



The three tools were completed as shown below, note only selected polylines are processed and that nodes\existing locations are avoided during the sampling process.



The random sites and positional data displayed; the table is showing only 3 fields for clarity but the tool will generate 12 fields of information.

Random sites

Positional Data


Run this model again and you generate a new scenario of random locations with positional information.  This is the power of model builder recording your workflow once, run many times.  You have also seen the usefulness of a selection on your river network to sample only the catchment of interest. If no polylines were selected then the whole network would have been sampled.

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