[postgis-users] Retrieving linestring data between endpoints

[Max Pyziur]

On Thu, 6 Sep 2012, Nicolas Ribot wrote:

> Hi,
>
> Maybe this thread about closing contour polylines can give some hints:
> http://postgis.refractions.net/pipermail/postgis-users/2012-May/034149.html

Much thanks. This script is worth exploring.

> Do you have sample data we could play with ?

The data that I sourced is here:
National Transportation atlas Database
http://www.bts.gov/publications/national_transportation_atlas_database/

Oak Ridge National Laboratory - CTA Network
http://cta.ornl.gov/transnet/RailRoads.html

I don't have readily available city point data; but that shouldn't be a 
challenge in finding.

My thinking now is to try and create a polygon with two endpoint, say 
Edmonton and Vancouver, and play with the diameter (20, 40 miles, etc.), 
trying to see which rail lines fall within the polygon. Possibly from 
that, I can construct a single linestring based some form of ownership 
(the BTS data is only for the US; the ORNL data is for North America).


> Nicolas

Much thanks again,

Max

> On 5 September 2012 19:15, Max Pyziur <pyz at brama.com> wrote:
>>
>> Greetings,
>>
>> I'm trying to figure out a way of constructing linestrings between
>> endpoints.
>>
>> Shapefile data for pipelines and railroads does not present continuous
>> lines; instead they are in the form of small line segments. The applications
>> are using data for roads, pipelines, or railroads.
>>
>> Interstate 70 is not one complete linestring between Washington DC and the
>> middle of Utah; instead it is a series of segments. The same with pipeline
>> and railroad data.
>>
>> The problem becomes more cumbersome (at least to me) when there is no
>> knowledge of the data between two points (say Edmonton and Vancouver) and
>> you want to see if there is a way to string a set of segments between two
>> points (to answer a question like is there a railline between Edmonton and
>> Vancouver)?
>>
>> I would appreciate any advice on how to proceed.
>>
>> Much thanks,
>>
>> Max Pyziur
>> pyz at brama.com
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