Hi Brandon,
I've read back a wee bit, and you might have answered these things already,
but I don't seem to able to find them so here goes:
* From your description I understand you effectively want to find all the
vertices that are unique (or those that aren't..). Is this correct?
* Why use a library the see if two points are at the same location? Is your
data input "forcing" you to use something like JTS?
Cheers,
Alexander
On 20 May 2013 22:23, brandon willard <[email protected]> wrote:
> I checked out JCS, but there was an odd dependency on JUMP and GUI-based
> operations. I ultimately cannot use a GUI, so it's really just the API
> I'm interested in; however, JCS' API was rather difficult to directly
> connect to my sequence of needs. Looking through the source did provide
> some insight, though.
>
> Now, I'm at a point where my requirements are better understood, so I'll
> try to clarify:
>
> 1. A set of input LineStrings need to be noded and/or snapped along
> their overlapping (within a tolerance) and co-directional segments only.
> 2. When LineStrings are noded/snapped, ShapeIds and a length index
> (relative to the parent LineString) need to be mapped to the resulting
> LineStrings.
>
> I've found most of what I need in JTS, like snapping through
> GeometrySnapper and noding through a custom SegmentStringMerger,
> IntersectionAdder and SegmentStringDisolver, but the former doesn't make
> for easy/any mapping or length indexing, and with the latter it's not
> apparent how one would "snap" (i.e. remove/dissolve overlapping lines) and
> end up with a connected line network. Also, JTS can't index the input
> LineStrings (by length in this case) if they're not simple, so I've had to
> completely node them individually and produce the index before noding the
> entire network. The "complete" noding I'm talking about is the JTS generic
> noding that introduces nodes for all intersections, which breaks things
> down more than I'd like.
> Naturally, I've gone the path of custom noding classes, since it's the
> only way I can create the mappings, but it's clearly not satisfying.
>
> Next, I need to create a directed graph that doesn't simply attach all
> in/out lines to shared vertices. There should be separate nodes for each
> direction so that u-turns aren't possible all over the place.
> Currently, I'm using DirectedLineStringGraphGenerator in OpenGeo, so those
> requirements aren't being fulfilled, and I expect I'll have to build a
> graph manually.
>
>
> On Thu, Feb 28, 2013 at 12:44 AM, David Zwiers <[email protected]>wrote:
>
>> Check out JCS (http://www.vividsolutions.com/jcs/) - there are a couple
>> graph structure tools. We've successfully built a polygonal coverage
>> manipulation model over JCS, so you should be able to do roughly the same
>> thing - just ignore the polygon faces and visualize how the polygon rings
>> are represented as a graph structure, should be similar to what you're
>> looking for.
>>
>> David
>>
>> On Wed, Feb 27, 2013 at 6:04 PM, brandon willard <
>> [email protected]> wrote:
>>
>>> Looking over my problem again, the result of a large union (e.g. using
>>> Geometry.union or CascadePolygonUnion) does produce the output lines I
>>> need, but then I lose any graph-like structure that would associate the
>>> input lines with those union-produced lines. (I wasn't clear about that
>>> requirement, sorry)
>>>
>>> How can I produce/maintain a relationship between the input lines and
>>> the "broken down" lines the union produces, without brute force checking
>>> overlaps between the two?
>>>
>>>
>>> On Wed, Feb 27, 2013 at 9:15 AM, Justin Deoliveira <[email protected]
>>> > wrote:
>>>
>>>> Hey Brandon,
>>>>
>>>> I am not 100% sure i undersand what you are looking for. Are you
>>>> looking to node the graph at intersections and line string endings?
>>>>
>>>> I am not sure if this will be what you are looking for but there is a
>>>> very cool effect that can be achieved with JTS. Basically take all the line
>>>> strings and join them into one multi linestring. Then union that multi
>>>> linestring with a single point that exists on it. The result is a multi
>>>> linestring where all the individual linestrings are properly noded at
>>>> intersections.
>>>>
>>>> -Justin
>>>>
>>>>
>>>> On Tue, Feb 26, 2013 at 9:47 AM, brandon willard <
>>>> [email protected]> wrote:
>>>>
>>>>> Hello,
>>>>>
>>>>> I'm working with a bunch of LineStrings that mostly overlap, and I
>>>>> would like to find a way to build a graph, or manipulate the geometries,
>>>>> so
>>>>> that it ends up with vertices from the points at which they stop
>>>>> overlapping.
>>>>> E.g. L1 = a->...->b->c, L2 = a->...->b->d and get vertices (a, b, c,
>>>>> d)
>>>>>
>>>>> I realize that it's possible to do this with a combination of JTS
>>>>> intersections/differences and whatnot, but I'm working with a lot of a
>>>>> LineStrings and was hoping there was something specifically for this that
>>>>> I
>>>>> passed over.
>>>>>
>>>>>
>>>>> ------------------------------------------------------------------------------
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>>>>> GeoTools-GT2-Users mailing list
>>>>> [email protected]
>>>>> https://lists.sourceforge.net/lists/listinfo/geotools-gt2-users
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> Justin Deoliveira
>>>> OpenGeo - http://opengeo.org
>>>> Enterprise support for open source geospatial.
>>>>
>>>
>>>
>>>
>>> ------------------------------------------------------------------------------
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>>> Make your web apps faster with AppDynamics
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>>>
>>
>
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