Still having problems creating a unidirectional buffers
To the kind person from ESRI who answered my question:
Link to the answer provided:
I have tried to work through the steps you provided and in theory your
methodology seems like the most appropriate way to get the results I'm
looking for. I seem to have hit an hurdle as the tool does not create
discreet polygons for each direction, instead there are polygons
within polygons (please refer to the attached map). I think its because
the roads are in such close proximity to each other the tool combines
the calculated direction for all the roads and only displays the
overlapped regions. True?
I have also attached the road file and would greatly appreciate it if
you could have a go to see if you get the same results.
Basically, I need to simulate the movement of a air pollution plume in
the W and NW direction (BTW the tool gets the directions wrong, think
its because the data is for southern hemisphere (Sydney)).
All this help is greatly appreciated.
Mapping Center Answer:
You do not state what the source of the pollution is. If it is all the roads, then that is more difficult to model, especially since it is likely that some portions of the roads will be producing more or less pollution than other portions of the roads. If it is a point source, like a factory, that is easier to model. Also, you state that the directions will be west and northwest. This also complicates the analysis. And finally, you do not state how strong the winds are, if there are impediments to the flow (topography, structures), and how far you think the pollution will be carried. All of these can be modeled but it would be more complicated than simply a buffer and a directional surface. The phenomena you are working with is a dynamic one so that is more challenging. I think you will have more luck with this analysis if you start with the Geoprocessing Resource Center to find out if others have tried to do something similar. Once you have the results of the analysis, we can help you to find the best way to symbolize the solution or solutions.
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