[UW-GIS-L] VBA question: start and end points of lines, and angles between line segments

[Timothy Nyerges]

Jack,
Thank you for providing this info.  It appears that we are assembling the
right information for making a good case about how to move forward with
the BoK.

For Sean's info...nothing absolutely concrete as yet, but it is
looking better about how the agreement about GIS&T BoK can be interpreted 
so we can move on with 2.0. However, there is more to be settled about 
where UCGIS stands in light of the agreement. Jack will be providing us a 
response from Gail Ross about her interpretation of the agreement and/or 
UCGIS position.

Tim


************************************************************************
Prof. Tim Nyerges, Geography, University of Washington
Box 353550, Seattle, WA, 98195, USA
voice: 206-543-5296, fax: 206-543-3313, email: nyerges at u.washington.edu
http://faculty.washington.edu/nyerges
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On Fri, 11 Apr 2008, Victor C. Van Hee wrote:


> I have a polyline file (road network) that I'm trying to automatically

> trace down relatively straight segments, carrying forward or smoothing

> traffic data which I have from another source.

>

> I've created a network dataset, and I'm using INetworkQuery to get

> adjacent segments, then taking the angle between the tangents at the

> 'from' junction of one segment and the 'to' junction of another.  If

> the angle between the tangents is small, I'm assuming that the road

> continues on.  The way I'm doing it seems incredibly complicated, and

> I'm wondering if there's an easier way to:

>

> 1) Find the start and end points of a  chain of segments (end of a

> line) programmatically.  In ArcView 3.1 there was an Avenue function

> called ReturnStart and ReturnEnd, but I can't see anything like that

> in ArcGIS 9 (VBA).  It might only work for 'routes' in 9 -- but I

> can't even see how to do that.  I've searched the developer site and

> google to no avail.  Of course, in my dataset, I don't really have any

> variables indicating where a road starts or ends.  ArcView 3.1 might

> have required this data in its line files -- I've  never used it.

>

> 2) Get the angle between the end of one segment and beginning of

> another without having to formally get the tangents.

>

> The above items would really help make my coding tasks much easier.

> If I could find starts and ends without going through every segment,

> this program would run about 10000% faster...

>

> Thanks.

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