Hi again,
On that matter: If you can isolate only the arc-part of your geometry,
you could that circular arc into the Postgis-function
"ST_MinimumBoundingRadius()" to detect center-point and radius. See
http://www.postgis.net/docs/manual-2.5/ST_MinimumBoundingRadius.html -
maybe worth a try?
Sample query:
SELECT ST_AsText(center), radius
FROM ST_MinimumBoundingRadius('CIRCULARSTRING(220268 150415,220227
150505,220227 150406)');
RESULT:
"POINT(220237.62195122 150455.5)" "50.6268293270462"
Greetings,
Andreas
Am 29.04.19 um 18:21 schrieb Cory Albrecht:
I tried saving a few layers that had arcs and circles (x,y, r coords),
but QGIS converts each curve to a bunch of straight line segments
instead of saving them as curves. :-(
On Mon, Apr 22, 2019 at 3:33 AM McDonaldR <mcdona...@angus.gov.uk
<mailto:mcdona...@angus.gov.uk>> wrote:
As your data is in PostGIS and assuming that they are arcs (curved
lines part of a circle) you could use some geometry and spatial
SQL functions to calculate the radius of any curve knowing the
coordinates of the end points of the curve.
To quote the pseudo code on the linked page:
“To calculate the radius of an arc, take the height -- "H" -- of
the arc and divide it by two. Call the result "C." Now take the
width -- "W" -- of the arc and square it by multiplying it by
itself. Call the result "D." Next multiply height, "H," by eight
and call this result "E." Divide "D" by "E" and call the result
"F." The radius of the arc is C plus F.”
https://sciencing.com/calculate-radius-curve-7804090.html
Could probably be wrapped in a function and run against any curve.
Ross
*From:*Qgis-user [mailto:qgis-user-boun...@lists.osgeo.org
<mailto:qgis-user-boun...@lists.osgeo.org>] *On Behalf Of *Cory
Albrecht
*Sent:* 19 April 2019 17:08
*To:* qgis-user@lists.osgeo.org <mailto:qgis-user@lists.osgeo.org>
*Subject:* Re: [Qgis-user] finding the radius of a curve
I'll give it a try. Thanks!
On Sun, Apr 14, 2019 at 7:52 AM Mike Flannigan <mikef...@att.net
<mailto:mikef...@att.net>> wrote:
Draw a circle and measure the diameter/radius.
Maybe use this plugin to create a circle:
https://plugins.qgis.org/plugins/CADDigitize/
Mike
On 4/13/2019 2:00 PM, qgis-user-requ...@lists.osgeo.org
<mailto:qgis-user-requ...@lists.osgeo.org> wrote:
> Hello all,
>
> I'm looking for a way to find the radius of a curve (for
roads, railyways)
> in QGIS. If it were a paper map I could do it with a
drafting compass
> (calipers to some) and a ruler, but this is a PostGIS layer.
>
> Any plugin recommendations or links to a set of steps to
accomplish this?
> Thanks in advance!
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