[GRASS-dev] [GRASS GIS] #3286: Add Line_height as a valid attribute in v.to.db

[GRASS GIS]

#3286: Add Line_height as a valid attribute in v.to.db
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  Reporter:  geografik    |      Owner:  grass-dev@…
      Type:  enhancement  |     Status:  new
  Priority:  normal       |  Milestone:  7.2.1
 Component:  Database     |    Version:  7.2.0
Resolution:               |   Keywords:  Line_height, v.in.db, kml
       CPU:  All          |   Platform:  All
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Comment (by mlennert):

 Replying to [ticket:3286 geografik]:
 > Imported kml files that include elevation data are structured generally
 as shown below in GRASS (this is an example of a contour line):
 >
 > east, north: -79.7630759471, 39.0874586371
 > DBT at corH:
 >  Type: Line
 >  Id: 885
 >  Length: 275.746
 >  Line_height: 698.602997
 >  Layer: 1
 >  Category: 885
 >  Driver: sqlite
 >  Database: /Users/sesMacBook/grassdata/KML/corH/sqlite/sqlite.db
 >  Table: DBT
 >  Key_column: cat
 >  Attributes:
 >    cat: 885
 >    cat_: 885
 >    tessellate: -1
 >    extrude: -1
 >    visibility: -1
 >
 > Elevation data is maintained in the Line_height field which is not a
 recognized attribute, and therefor precludes any further use of these data
 in GRASS - beyond simple display and labling.  3D analysis, for example,
 is not possible.  The suggested improvement to v.to.db would add
 Line_height to the list of attributes considered in this module so that
 the elevation data could become part of the recognized feature attributes
 and be useful in other modules.


 Actually, Line_height is not a "field" in the data. v.what calculates the
 minimum and the maximum height of all the vertices of a line and either
 outputs both, or, if they are equal, only one value.

 The question this raises, therefore, is: which "height" is the most
 relevant for a line ? Should it be the mean height of all vertices ?
 Should v.to.db provide lheight_min, lheight_mean and lheight_max ?

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Ticket URL: <https://trac.osgeo.org/grass/ticket/3286#comment:1>
GRASS GIS <https://grass.osgeo.org>