[postgis-users] Prorate values along a line feature based on length.

[Basques, Bob (CI-StPaul)]

Wow, that’s the first time I’ve heard of that function, looks like it is exactly what I’m looking for.  I’ll try that out.

Thanks Simon, I’ll post results. . . .

Bobb



From: postgis-users <postgis-users-bounces at lists.osgeo.org> on behalf of Simon Norris <snorris at hillcrestgeo.ca>
Reply-To: PostGIS Discussion <postgis-users at lists.osgeo.org>
Date: Wednesday, January 5, 2022 at 11:17 AM
To: PostGIS Discussion <postgis-users at lists.osgeo.org>
Subject: Re: [postgis-users] Prorate values along a line feature based on length.

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Bobb,

It sounds like you want to add measures from the endpoints:
https://postgis.net/docs/ST_AddMeasure.html

Then grab the interpolated elevations with something like this:
SELECT ST_Z(ST_PointN(geom, generate_series(1, ST_NPoints(geom) - 1))) AS elevation

Simon




On Jan 5, 2022, at 9:03 AM, Basques, Bob (CI-StPaul) <bob.basques at ci.stpaul.mn.us<mailto:bob.basques at ci.stpaul.mn.us>> wrote:

All,

Ok, this is sort of a weird one (to me).

I have a feature dataset of MutliLineStrings, all with no Z value, but with a Elevation attribute on each end.   I need to prorate the elevation for each vertex along the line based on the distance for either/or each of the ends.

I was planning on attaching this from the client side originally, but though I would ask here if anyone has tried a SQL approach to extracting/creating.

Maybe recreate the feature with the attiributes on the fly?  Then extract the vertex info.  The intent is to import into a CAD application and build a 3D CAD model.

Anyway, any thoughts?

Bobb



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