5 replies to this topic

[Steve Young]

Hi,

I'm using the ArcInfo 9.1 'Locate linear features along route' tool to create an event table of records where a linear feature, e.g. a road comes with 50m of a route. Unfortunately I'm getting strange results with the table record commencing when the linear feature is more than 50m from the route and ending when it is still within 50m. The attached image illustrates. I've tried different computers and created different routes and lines, but get the same results. I'm not wedded to doing this analysis using this methodology using this software, but I do need to get it done quickly. If anyone has any ideas on either what's happening or an alterative procedure then I would be grateful.

Apart from Arcinfo I have Mapinfo and open source GIS tools to hand.

Cheers,

Steve
 line_ref.gif   17.22K   94 downloads

[Steve Young]

I get to answer my own post (for not thinking of the answer sooner ) and (for not wasting too much of anyone else's time)

Buffering my linear feature by the adjacency distance I want to measure then using the events wizard to create an events table of my buffer along the route gives me what I want with no weirdness. I'd still like to know why the 'Locate linear features along route' was treating me and my data so badly, but at least I have a decent alternative.

Cheers,

Steve

[frax]

Does the routine you did first split up the roads into segments where they intersect the adjacancy distance? I am not sure I understood exactly what you wanted to do and what the problem was... If I would have done this, I would have tried buffers first and I would have missed that there was a built-in tool for this!

[Steve Young]

Hi Frax,

The first routine was using a wizard, so I could only guess what it was doing behind the scenes. I'm still puzzled that I got consistently awful results from what on the surface appeared to be a straightforward application of the tool. I suspect there's a bug in the routine that ignores the input data tolerance. That said the more intuitive method is as you suggest is to buffer first, so it's to some extent redundant.

Steve

[Foxtrot]

I guess I have a similar task to solve: I have to find a route from point A to B along roads and then find on how long distance there is forest next to the route.

Does anybody has any idea how to make this happen in MapInfo? or what do you suggest to use?

[gregsd]

I guess I have a similar task to solve: I have to find a route from point A to B along roads and then find on how long distance there is forest next to the route.

Does anybody has any idea how to make this happen in MapInfo? or what do you suggest to use?

Foxtrot,

There are a couple of apps you can use to find routes from A to B using a road network:

RouteFinder

DriveTime

You second question is a bit trickier, but you could do some fancy SQL to find where the route intersects the forest polygons and return the length.

Greg