It isn't the networ because the tool works fine when I interpolate the
results as points instead of a raster.
I think it is in how it bulbs the tin, I will have to do more checking.

On Wed, 25 Mar 2020 at 17:27, kirk <> wrote:

> Nicolas is right. There is  good chance the topology is a bit messed up.
> You can spend Lot of time fixing it up so I would suggest downloading the
> gis basmap layers from the pei government website. There us a large scale
> database for Charlottetown  (1:2000) that will work better for you. Just
> search gis database pei.
> Kirk
> Sent from my Samsung Galaxy smartphone.
> -------- Original message --------
> From: Nicolas Cadieux <>
> Date: 2020-03-25 12:35 PM (GMT-04:00)
> To: Tyler Veinot <>
> Cc: QGIS User List <>
> Subject: Re: [Qgis-user] Isochrones
> Hi,
> The first thing I would do is to check the network integrity.  Perhaps
> some road are not connected (snapped).  You also need a snap and break at
> every intersection. You can do some of this by exporting all the end node.
> Check for multiline vs lines. You can split all of those in the vector
> menu.  Your problems are likely linked to a bad network topology. Users of
> that network could perhaps confirm this? I have used it but not for this
> type of stuff.
> Nicolas Cadieux
> > Le 25 mars 2020 à 10:22, Tyler Veinot <> a écrit :
> >
> > 
> > All;
> > I have a network, Canada National Road Network it is a free download,
> that I am trying to use for PEI and the City of Charlottetown to find out
> what area is within X time of various points of interest. I used Here for
> QGIS to get the initial result but QGIS has a tool built in Network Analyst
> that has Service Area from Network and from Point, also and QNEAT that has
> 6 isochrone tools for doing exactly what I am trying to do. For some reason
> though the results don't seem to match the network. I would expect the from
> the point of origin the shortest times to be along the lines and radiate
> out.
> > What tools are you guys using to do this kind of work? Do my values for
> forward backward both direction need to be numeric? Any tutorials on using
> these tools?
> > Thanks;
> > Tyler
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