Service areas do not include facilities

[michellepop]

Hi there,

I am trying to create service areas for 1000 facilities for a break of 400 m. Everything works fine, but I noticed that several facilities have service areas that do not contain the facilities themselves (really weird).

I should note that these facilities are located further away from the street network. I used the default tolerance of 5000 m and I selected the "detailed polygons" option with a "trim value" of 100 m (it is not clear to me what that "trim" value refers to). Does anybody know what I am doing wrong here?

Thanks!

[michellepop]

I believe that this is going on because some facilities are located further away from the network (e.g., 200-300m from the nearest network location) so a service area of 400 m for one such facility would start from that network location on, away from the facility. Any thoughts about this?

[JaySandhu]

Service area polyons are generated around the lines that are traversed from the start location (facility).
When the facilities are not on the network, say 5000 meters away and you are only asking for a 400 m service area, then the polygon will not cover the facility. However do note, that it covers the start location, or the location where the facility was located on the network.

As far as trim, for a 400 m service area, I would set it around 25 meters. And what it does is trim the service area polygons to better hug the outer set of edges. Normally the shape of the polygon is dictated by finding a boundary between the streets that were traversed and streets that were not traversed. This can result in a jagged polygon in some areas. Using trim keeps the polygon boundary within a certain distance from the traversed edges.

You can read more about the Trim towards the bottom of this web help page:
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Service_area_analysis/0047000000480000...

Jay Sandhu

[michellepop]

Hi Jay,
Thank you so much for your detailed answer. This is really helpful! I will use a trim value of 25 m.
Thanks again!