Opened 3 years ago

Last modified 11 months ago

#3419 new defect

v.to.db sinuous

Reported by: jradinger Owned by: grass-dev@…
Priority: normal Milestone: 7.4.5
Component: Vector Version: 7.2.2
Keywords: v.to.db, shape metrics Cc:
CPU: All Platform: All

Description

The option of v.to.db to calculate sinuosity (sinuous) seems to be calculated based on features (i.e. feature ids) rather than on cats (e.g. as length is calculated). Thus, only reasonable results are calculated if a cat consists of only one feature. For connected lines that consist of more than one feature (lines) it is unclear how the sinuosity index is calculated (based on last processed feature? average over all sub-lines). For connected lines that share one cat the sinuosity should probably be calculated based on a polyline of these lines sharing a common cat.

This might be also related to https://trac.osgeo.org/grass/ticket/3102

Change History (3)

comment:1 in reply to:  description Changed 3 years ago by mmetz

Replying to jradinger:

The option of v.to.db to calculate sinuosity (sinuous) seems to be calculated based on features (i.e. feature ids) rather than on cats (e.g. as length is calculated). Thus, only reasonable results are calculated if a cat consists of only one feature. For connected lines that consist of more than one feature (lines) it is unclear how the sinuosity index is calculated (based on last processed feature? average over all sub-lines).

The sinuosity index is sinuosity of the last feature processed. For multiple lines with the same category, how should sinuosity be calculated? Average of all sinuosities or sum of all line lengths / sum of all endpoint distances?

Line slope is currently the sum of all line slopes, that does not seem right.

Azimuth is the azimuth of the last feature processed. Since azimuth is an angle, a simple average over all lines with the same category would not work.

For connected lines that share one cat the sinuosity should probably be calculated based on a polyline of these lines sharing a common cat.

In this case polylines would need to be built first, before running v.to.db.

comment:2 Changed 2 years ago by martinl

Milestone: 7.2.4

comment:3 Changed 11 months ago by sbl

Milestone: 7.2.47.4.5

Markus explanation answered the question-part of the ticket quite well. However, a warning message might be helpful for the users and then there is the issue with slope Markus mentioned...

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