topic Error message: Gaps have been detected... in ArcGIS Network Analyst Questions

Error message: Gaps have been detected...

JoeBorgione — Wed, 29 Aug 2012 15:39:37 GMT

When I run any kind of solve, I get the following message:

Warning: Gaps have been detected in the cumulative impedance values of the output. This can occur due to the presence of positive-impedance junctions, turns, or additive point barriers along the output edges. Measures have been disabled for output in this case

Can anyone give a clue as to where to start looking?

Edited an hour or so after original post....

This is really just a warning; what it's talking about is a mystery, but I just turned off warnings in the Network Analyst Toolbar/options. Fixed!

Remember the song that 'Kip' sings at his wedding in Napolean Dynamite? ..."Yes I love technology..."

Re: Error message: Gaps have been detected...

PatrickStevens — Thu, 30 Aug 2012 14:22:24 GMT

I love that error message! That one was always my favorite, because of its length and complexity. It was like an error novella. We knew it was a problem, so it is gone now in 10.1. I'm not sure if it was service packed back to 10.0. I'll check that.

As for what it means, your output shape is set to "True Shape with Measures". This gives you not just the route shape, but linear referencing M values along the shape. For example, for a 10 minute long route, you can see where you are 2 minutes, 5 minutes, 7, minutes along, etc.

It used to be a problem when there was sudden additive cost along a route that should have M values. The error message lists "positive-impedance junctions, turns, or additive point barriers". Those are three examples of a place where you might add time to your route. For example, an additive cost barrier of 2 minutes turns your route from 10 to 12 total minutes. Previously, we couldn't handle generating Ms where, using the 10 minute route example, it went from 0 to 5 minutes, then had a 2 minutes additive point, then went from 7 to 12 minutes.

When additive costs were encountered, we still solved the route, but we disabled M values in the output route shape. A warning would be generated letting you know that, even though you specified that Ms should be in the output shape, they will not be present.

So, change your output shape to "True shape", instead of "True shape with measures." Then, you can turn warning messages back on.

Re: Error message: Gaps have been detected...

JoeBorgione — Thu, 30 Aug 2012 14:53:39 GMT

I love that error message! That one was always my favorite, because of its length and complexity. It was like an error novella. We knew it was a problem, so it is gone now in 10.1. I'm not sure if it was service packed back to 10.0. I'll check that.

As for what it means, your output shape is set to "True Shape with Measures". This gives you not just the route shape, but linear referencing M values along the shape. For example, for a 10 minute long route, you can see where you are 2 minutes, 5 minutes, 7, minutes along, etc.

It used to be a problem when there was sudden additive cost along a route that should have M values. The error message lists "positive-impedance junctions, turns, or additive point barriers". Those are three examples of a place where you might add time to your route. For example, an additive cost barrier of 2 minutes turns your route from 10 to 12 total minutes. Previously, we couldn't handle generating Ms where, using the 10 minute route example, it went from 0 to 5 minutes, then had a 2 minutes additive point, then went from 7 to 12 minutes.

When additive costs were encountered, we still solved the route, but we disabled M values in the output route shape. A warning would be generated letting you know that, even though you specified that Ms should be in the output shape, they will not be present.

So, change your output shape to "True shape", instead of "True shape with measures." Then, you can turn warning messages back on.

Thanks Patrick!

It just took me totally by surprise; we were having an issue with a station not routing to a call it should have gone to (through CAD) and ran it manually in ArcMap. My only thought was "Oh, $*** ! What Happened?!"

I will uncheck the true shape with measures when I get back there next week....

Re: Error message: Gaps have been detected...

PatrickStevens — Thu, 30 Aug 2012 15:03:11 GMT

One more quick thing. The warning message is not just gone in 10.1, the thing we are warning about has been fixed. Measures are no longer disabled in the presence of additive costs.

Re: Error message: Gaps have been detected...

PatrickStevens — Thu, 30 Aug 2012 16:32:13 GMT

The fix is only in 10.1+. It is not service packed back to 10.0.