[QGIS-Developer] Buffer Algorithm (Buffer distance of output polygon is not equal to the Distance parameter)

[Ben Hur Pintor]

Hi everyone.

I apologize if this has been asked before but I would just like to clarify
if this is how the buffer algorithm in QGIS should function.

*Issue:* The actual distance from the input layer to the buffer polygon
created by the Buffer processing tool (and v.buffer) is not equal (only
around 80%) to the Distance parameter provided in the said tool.

*Example:* My coordinate reference system is WGS84/UTM Zone 51N (EPSG:
32651). I create a 100m buffer around a point but when I measure the
resulting circle, its edge is only ~80m from the point (see buffer-point
and buffer-point-distance below).

 buffer-point.png
<https://drive.google.com/file/d/1SAptLcRKnGVc8zyESkl-sJZ23a5OWEsy/view?usp=drive_web>

 buffer-point-distance.png
<https://drive.google.com/file/d/1aQ0mfadGnEzISkPnu-GGX9SUu1GXhGMs/view?usp=drive_web>

I create a 50m buffer around a line but when I measure the resulting
buffer, its edge is only ~40m from the line (see line-buffer and
line-buffer-distance below).

 line-buffer.png
<https://drive.google.com/file/d/11cNTRNbHxB3cFCaZEhXDWqKYEdWJX31K/view?usp=drive_web>

 line-buffer-distance.png
<https://drive.google.com/file/d/1PGRabSqF-zrOCpAboncQ_yQxx_0ulByN/view?usp=drive_web>


Clarifications will be much appreciated. Maybe I just missed some part of
the documentation.

Thank you.

Sincerely,
Ben Hur

-- 
---

*Ben Hur S. Pintor*
bnhr.xyz


Consultancy · Training & Support · Development & Innovation
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