Add Line_height as a valid attribute in v.to.db

[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@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.

[mlennert]

Replying to 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@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 ?