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<p>Hi Stewart:</p>
<p>You could write a simple script using python or modeler to do
what you are looking for. I would reproject to a UTM or similar
projection and then the math for each segment gets easier.</p>
<p>Reach out to me privately as I have some ideas on how to
implement it.</p>
<p>Kirk Schmidt</p>
<p><a class="moz-txt-link-abbreviated" href="mailto:kirk@nortekresources.com">kirk@nortekresources.com</a> <br>
</p>
<div class="moz-cite-prefix">On 3/30/2023 4:56 PM, Stewart Holt via
QGIS-User wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAFnvfO0+EbVcEc3q0a4EWO5B6dBXKgAo+WQXn=NyAemsNsJENw@mail.gmail.com">
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<div dir="ltr">
<div>Tim,</div>
<div><br>
</div>
<div>Depending on how the GPS data was collected for the trail,
your line shape may be longer than the actual trail. Each GPS
point has some error and if the points were collected at one
per second, the additional length caused by points being off
the centerline, could be significant. GPS height is more noisy
with error than the horizontal distance. That can contribute a
lot of extra length. I use a sub-meter GNSS unit and filter
the points to be no less than 10 feet apart. I add elevation
from a USGS layer using the QGIS drape function because that
is more accurate than the GPS height. By doing this, the 3D
length is within about 1% as compared to a measuring wheel.</div>
<div><br>
</div>
I made the earlier post for work I do for the Appalachian Trail.
What I want is a way to calculate the 3D distance from one point
to the next and put the running total in the M value of each
point. In my case, the layers are in geo coordinates and would
require the horizontal distance be calculated with lat/lon. I
read the descriptions of every plugin and determined that
nothing currently does what I wanted. I am a programmer but have
very little Python experience. I did get one response which was
helpful in writing plugins but have not yet pursued it. An
example of a plugin which takes a vector layer input, does
something (or nothing) with it and creates an output layer would
be a good starting point. If I can achieve what I want to do,
what you need would be a simple change.
<div><br>
</div>
<div>Stewart Holt</div>
<div>Georgia Appalachian Trail Club</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Thu, Mar 30, 2023 at
3:10 PM Tim Fearn via QGIS-User <<a
href="mailto:qgis-user@lists.osgeo.org"
moz-do-not-send="true" class="moz-txt-link-freetext">qgis-user@lists.osgeo.org</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi
everyone,<br>
I’m trying to use the qchainage plugin to create ½ mile
markers along a vector line that represents a trail. The line
is a single feature with no multi-parts or dangles. It is
about 318 miles long so I would expect right around 636 points
if there is one every half mile. My project default is set to
miles for length measurements as is the qgis main preference.
I set the unit measurement to miles and input .5 as the
interval. I continually get 771 points instead of the
expected 636. Also when I use the automatic labeling feature
of the plugin it appears to be in degrees not an aggregate
mileage.<br>
<br>
Several weeks ago a fellow had queried the list on the
same subject. He was working with the Appalachian Trail I
believe and wanted to place points at given distances. No one
seemed to really understand so I’m hoping that if anyone
remembers the original poster, and has come up with any
thoughts or other ideas it would be much appreciated. This is
something that can be done for sure. All of the National
Scenic Trail maps in this country are demarcated with some
form of mile or half mile makers which when labeled show the
accumulated distance.<br>
<br>
Hoping for some traction on this. I’ve only just started
learning python so I wouldn’t describe myself as a programer
and am looking for a relatively simple solution.<br>
<br>
With much gratitude,<br>
<br>
Tim Fearn<br>
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<pre class="moz-signature" cols="72">--
Kirk Schmidt, MScF, BScF, RPF
General Manager
Nortek Resource Solutions Inc.
26 Church Road
Sutherlands River, NS
B0K 1W0
Tel (902) 922.3607
Email: <a class="moz-txt-link-abbreviated" href="mailto:kirk@nortekresources.com">kirk@nortekresources.com</a>
Web: <a class="moz-txt-link-abbreviated" href="http://www.nortekresources.com">www.nortekresources.com</a></pre>
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