[Qgis-user] rephrased;. import 3D line into a shapefile?

[mtnbiketrail at zzz.com]

Thanks for the suggestions. Ultimately, I wanted to have a 3D 
visualization using a DEM. I was planning on using UTM. This will take a 
lot of thought on my part, being a beginner, so it will take a while to 
accomplish. Right now I don't have QGIS GRASS plugin working. So I have 
a long way to go. Message: 6 Date: Wed, 18 Mar 2009 22:46:16 -0500 From: 
David Fawcett <david.fawcett at gmail.com> Subject: Re: [Qgis-user] 
rephrased;. import 3D line into a shapefile? To: mtnbiketrail at zzz.com, 
Qgis-user at lists.osgeo.org Message-ID: 
<ed718af50903182046m5301788cv4448695939a3406a at mail.gmail.com> 
Content-Type: text/plain; charset=ISO-8859-1 Tom, You have laid out an 
interesting (fun) problem. I don't have a solution for you, but a few 
thoughts on how I would approach it. 1. I am not sure how you want to 
display the 3D shape in QGIS. If you are just going to symbolize the 
depth by coloring the line segments, you could get by with a 2D 
shapefile and an attribute for depth. 2. I would likely write a python 
script using the ogr python module to calculate the x,y,z values for 
each vertex in your line and then create the shapefile. 3. Instead of 
using lat/lon for your spatial reference system, you may want to think 
about projecting your original point to a coordinate system like UTM. 
This should make your calculations easier. David. On Wed, Mar 18, 2009 
at 1:46 PM, <mtnbiketrail at zzz.com> wrote:

> > Okay, let me rephrase the question. I did look at ogr2ogr, csv file import.
> > I have a 3D line, but only the beginning vertex has x,y,z. The line is a
> > survey of a cave, so only the entrance has a latitude, longitude, and z
> > coordinate. The rest are relative to the control point. Any suggestions on
> > how to import that?
> > Tom
> >
>   
>> >> Subject: [Qgis-user] import 3D line into a shapefile?
>> >> To: qgis-user at lists.osgeo.org
>> >> Message-ID: <49BFE4B3.60900 at zzz.com>
>> >> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>> >>
>> >> Hi, I'm a beginner user.
>> >> Is it possible to import a 3D line into QGIS? I have the text file with
>> >> distance, compass, and azimuth and want to have it show as a shapefile(?) in
>> >> 3 dimensions inside QGIS.  How would I go about doing that? Also, correct
>> >> me, don't I have to use the correct datum to show 3d. Like WGS84? I don't
>> >> think NAD83 can handle 3D?
>> >>
>> >> thanks,
>> >> Tom
>> >>
>>     
> >
> > _______________________________________________
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> > Qgis-user at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/qgis-user
> >
>   


------------------------------

Message: 7
Date: Wed, 18 Mar 2009 22:45:01 -0700
From: Alex Mandel <tech_dev at wildintellect.com>
Subject: Re: [Qgis-user] rephrased;. import 3D line into a shapefile?
To: Qgis-user at lists.osgeo.org
Message-ID: <49C1DBDD.2010301 at wildintellect.com>
Content-Type: text/plain; charset=ISO-8859-1

This sounds like a classic survey problem. Tools that deal with this are
often called COGO (I don't remember what that means)
While many tools and algorithms exist for doing distance and bearing,
which will allow to you plot changes in x,y of whatever plane you're
working in, the z value would need to be incorporated as an attribute.

So I would say as David stated, start with a tool that calculates an x,y
based on a distance and bearing from the previous point and tack on a z
calculation to add/subtract from the previous value. This will allow you
to use standard 3D visualization tools in GRASS, R or whatever else you
feel like using.

I think there's a distance/bearing tool in one of the plugins, shouldn't
be too hard to right, algorithm's are all over the place, GRASS has one
for sure.

Alex