On Thu, Aug 23, 2012 at 11:24 AM, Melpati, Muni < muni.melp...@dot.state.fl.us> wrote:
> In a shapefile, especially routes, you can have user defined measures > (m-values, usually in miles), they might not be same when you measure the > two dimenstional line, from start to end vertices of any feature. These > shapefiles would have begin and end post fields as attributes.**** > > It is not the case for any shapefiles with line types since two > dimensional measures deviate from real distance from point a to point b. > Moreover they would not be in miles.**** > > I was asking if I import a shapefile of “polyline M” into PostGIS would I > be able to get measure in miles given a point or would I be able to get > points given a measure in miles? Orelse there is different mechanism in > PostGIS > If your shapefile has an M value and you use shp2pgsql to import it into PostGIS, it will still have the M values intact. ogr2ogr and some other tools do not carry forward the M value. > **** > > to the same job. If so how it is done. I know there are few methods to > retrieve a mile point or a measure give a point in PostGIS. Doesn’t this > require calibrating the route, first, like I found out in this link ( > http://www.faunalia.com/lrs). Sorry for not being very clear in my > previous question. I thought people might have confounded this situation > and can easily understand it. Please let me know if still do not understand > or help me if you can. > You can use all the linear referencing tools on this data using that measure value. See http://postgis.org/documentation/manual-2.0/reference.html#Linear_Referencing > **** > > ** ** > > Date: Tue, 21 Aug 2012 21:12:04 -0400**** > > From: "Paragon Corporation" <l...@pcorp.us>**** > > Subject: Re: [postgis-users] created linear referencing system**** > > To: "'PostGIS Users Discussion'"**** > > <postgis-users@postgis.refractions.net>**** > > Message-ID: <527D56A990434161A53D6CA92B3D9ED9@O>**** > > Content-Type: text/plain; charset="us-ascii"**** > > ** ** > > Muni,**** > > **** > > Not sure what you are asking and maybe others have a similar problem**** > > understanding. That might be why you haven't received an answer.**** > > **** > > What do you mean by linear reference capable? All spatial data that is of > **** > > linestrings can be linearly referenced. Are you talking about a specific* > *** > > tool you are using?**** > > **** > > when you load your data from shape file to PostGIS, the data is still the* > *** > > same. If it had linestrings before, it should still have linestrings.**** > > ** ** > > _____ **** > > ** ** > > From: postgis-users-boun...@postgis.refractions.net**** > > [mailto:postgis-users-boun...@postgis.refractions.net<postgis-users-boun...@postgis.refractions.net>] > On Behalf Of Melpati,**** > > Muni**** > > Sent: Tuesday, August 21, 2012 4:07 PM**** > > To: postgis-users@postgis.refractions.net**** > > Subject: [postgis-users] created linear referencing system**** > > ** ** > > ** ** > > ** ** > > Hi,**** > > ** ** > > I have asked this question before and could not get straight answer. I have > **** > > a shape file which Linear reference capable. How to import such data?**** > > ** ** > > If I load the data using shape file loader, would the imported data is**** > > linear reference capable. If not how to recreate linear referencing system > **** > > on imported data?**** > > ** ** > > _______________________________________________ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users > > -- ************************************ David William Bitner
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