'Re: [postgis-users] Linear referencing capability'

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List: postgis-users
Subject: Re: [postgis-users] Linear referencing capability
From: David William Bitner <bitner () gyttja ! org>
Date: 2012-08-23 18:33:58
Message-ID: CAEqvsZsTnUV0vtCPrn7qzO-5_-dm8oq-5LVo=E2y9+KDZ1NZ0w () mail ! gmail ! com
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On Thu, Aug 23, 2012 at 11:24 AM, Melpati, Muni <
Muni.Melpati@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" <lr@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-bounces@postgis.refractions.net****
>
> [mailto:postgis-users-bounces@postgis.refractions.net<postgis-users-bounces@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

[Attachment #5 (text/html)]

<br><br><div class="gmail_quote">On Thu, Aug 23, 2012 at 11:24 AM, Melpati, Muni \
<span dir="ltr">&lt;<a href="mailto:Muni.Melpati@dot.state.fl.us" \
target="_blank">Muni.Melpati@dot.state.fl.us</a>&gt;</span> wrote:<br><blockquote \
class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc \
solid;padding-left:1ex">

<div lang="EN-US" link="blue" vlink="purple"><div>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

</div></div></blockquote><div> </div><div>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.</div>

<div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px \
#ccc solid;padding-left:1ex"><div lang="EN-US" link="blue" \
vlink="purple"><div>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 (<a href="http://www.faunalia.com/lrs" \
target="_blank">http://www.faunalia.com/lrs</a>). 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.

</div></div></blockquote><div>You can use all the linear referencing tools on this \
data using that measure value. See <a \
href="http://postgis.org/documentation/manual-2.0/reference.html#Linear_Referencing">h \
ttp://postgis.org/documentation/manual-2.0/reference.html#Linear_Referencing</a></div>

<div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 \
.8ex;border-left:1px #ccc solid;padding-left:1ex"><div lang="EN-US" link="blue" \
vlink="purple"><div><p><u></u><u></u></p><p><u></u> <u></u></p>

<p>Date: Tue, 21 Aug 2012 21:12:04 -0400<u></u><u></u></p><p>From: &quot;Paragon \
Corporation&quot; &lt;<a href="mailto:lr@pcorp.us" \
target="_blank">lr@pcorp.us</a>&gt;<u></u><u></u></p><p>Subject: Re: [postgis-users] \
created linear referencing system<u></u><u></u></p>

<p>To: &quot;&#39;PostGIS Users Discussion&#39;&quot;<u></u><u></u></p><p>      \
&lt;<a href="mailto:postgis-users@postgis.refractions.net" \
target="_blank">postgis-users@postgis.refractions.net</a>&gt;<u></u><u></u></p><p>

Message-ID: &lt;527D56A990434161A53D6CA92B3D9ED9@O&gt;Content-Type: \
text/plain; charset=&quot;us-ascii&quot; \
Muni, Not sure what you are \
asking and maybe others have a similar problem understanding. \
That might be why you haven&#39;t received an answer. \
What do you mean by linear reference capable? All spatial data \
that is oflinestrings 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 thesame. If \
it had linestrings before, it should still have linestrings.

<p><u></u> <u></u></p><p>  _____  <u></u><u></u></p><p><u></u> <u></u></p><p>From: <a \
href="mailto:postgis-users-bounces@postgis.refractions.net" \
target="_blank">postgis-users-bounces@postgis.refractions.net</a><u></u><u></u></p>

<p>[<a href="mailto:postgis-users-bounces@postgis.refractions.net" \
target="_blank">mailto:postgis-users-bounces@postgis.refractions.net</a>] On Behalf \
Of Melpati,<u></u><u></u></p><p>Muni<u></u><u></u></p><p>Sent: Tuesday, August 21, \
2012 4:07 PM<u></u><u></u></p>

<p>To: <a href="mailto:postgis-users@postgis.refractions.net" \
target="_blank">postgis-users@postgis.refractions.net</a><u></u><u></u></p><p>Subject: \
[postgis-users] created linear referencing system<u></u><u></u></p><p><u></u> \
<u></u></p>

Hi, \
I have asked this question before and could not get straight answer. I \
havea shape file which Linear reference capable. How to import \
such data?

If I load the data using shape file loader, would the \
imported data islinear reference capable. If not how to recreate \
linear referencing systemon imported data?

<p class="MsoNormal"><u></u> \
<u></u></p></div></div><br>_______________________________________________<br> \
postgis-users mailing list<br> <a \
href="mailto:postgis-users@postgis.refractions.net">postgis-users@postgis.refractions.net</a><br>
 <a href="http://postgis.refractions.net/mailman/listinfo/postgis-users" \
target="_blank">http://postgis.refractions.net/mailman/listinfo/postgis-users</a><br> \
<br></blockquote></div><br><br clear="all"><div><br></div>-- \
<br>************************************<br>David William Bitner<br>

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