topic Re: service area in ArcGIS Network Analyst Questions

service area

thainamota — Wed, 26 Aug 2020 06:53:57 GMT

Buongiorno

I am trying to use network analysis - service area - to create a polygon based on distance, for example 1000 meters.

In my case, dot = schools. So I want to see an area covered by 1000 meters.

There's one thing I can't understand... Why does it generate some weird clippings? as in the photo

Thank you so much!

Thai

serviceareapolygons‌networkanalysis footprint polygon nearest distance

Re: service area

DanPatterson — Wed, 26 Aug 2020 08:18:37 GMT

Make Service Area Analysis Layer (Network Analyst)—ArcGIS Pro | Documentation

did you specify a polygon_trim_distance?

are there roads and other locations outside your image? or have you clipped this image?

Re: service area

thainamota — Wed, 26 Aug 2020 09:28:46 GMT

Hi Dan,

thanks to your answer!
no, I didn't use trim.

To create a network I used arcstra which are the roads.
There are no roads or places outside

In the video I show what I used as parameter...many things remain by default.

thanks a lot!

(view in My Videos)

Re: service area

MelindaMorang — Wed, 26 Aug 2020 15:08:10 GMT

Spikes like that are a common artifact of the polygon generation algorithm in ArcMap. We have implemented a new and improved polygon generation algorithm that makes the Service Area polygons look more bubbly or cloudy and less spikey. You can access the new algorithm in one of two ways:

1) In ArcMap, open the properties of your network dataset. On the Optimizations tab, turn on the box for the Service Area Index. You might need to re-build your network dataset after this, but I can't remember. Future Service Areas using this network should use the newer algorithm.

2) Use ArcGIS Pro instead of ArcMap. ArcGIS Pro Service Areas always use the new algorithm.

Re: service area

thainamota — Fri, 28 Aug 2020 09:59:25 GMT

Melinda many thanks for your reply!
I used the algorithm but nothing happened...maybe the algorithm has difficulty or is not adapted to arcmap 10.5.

I noted that if I used 'not overlapping' instead of 'merge by break value' genereted less spikes.

Re: service area

MelindaMorang — Fri, 28 Aug 2020 14:56:43 GMT

Hmm, that still does not look like polygons produced by the newer algorithm. Is your polygon detail level is set to Detailed? Or do you have hierarchy turned on? Either of those things will prevent the use of the newer algorithm in ArcMap.

Do you have a polygon trim distance set? If not, you should set one, and that may help reduce spikes.

Re: service area

thainamota — Tue, 01 Sep 2020 12:26:25 GMT

I tryied as you say...its the same!

I noted that when I flag 'Service Area Index' as you indicate, after some seconds is not select anymore...its seems that don't remain selected

Re: service area

MelindaMorang — Tue, 01 Sep 2020 15:04:25 GMT

I can see in the video above that you are not using trim and that you have selected Detailed polygons. The Detailed polygons in ArcMap will never use the new Service Area algorithm. If you want to use detailed polygons and see the nice new polygons, you need to use ArcGIS Pro.

If you want to get rid of spikes using your existing Service Area layer in ArcMap, I suggest you set a polygon trim of something like 50-100 meters.

Re: service area

thainamota — Tue, 08 Sep 2020 12:56:53 GMT

Hi Melinda, I followed all your instructions (as I show in this new video) The result generated a unique polygon when I used trim + merge polygon, without stranges spikes. I also used trim+no merge, which generated some internal clippings.
In neither of them the result is great but I understood the differences!
thanks so much!

Re: service area

thainamota — Tue, 08 Sep 2020 14:27:45 GMT

(view in My Videos)

Re: service area

MelindaMorang — Tue, 08 Sep 2020 15:19:29 GMT

From this video, I see that your network dataset has an unknown spatial reference. This could also be part of the problem. You should always give your data a spatial reference.

Re: service area

thainamota — Thu, 15 Oct 2020 14:06:20 GMT

Hi Melinda,

sorry for my delay, in this period we have been work with many urban themes to the new Urban plan

many thanks for your support...yes, 'unknown spatial reference' was the problem.

Thanks