Provided by: grass-doc_7.6.1-3_all bug

NAME

       v.to.db  - Populates attribute values from vector features.

KEYWORDS

       vector,  attribute  table,  database,  area, length, perimeter, coordinates, bounding box,
       category

SYNOPSIS

       v.to.db
       v.to.db --help
       v.to.db  [-psc]  map=name   [layer=string]     [type=string[,string,...]]    option=string
       columns=name[,name,...]    [units=string]     [query_layer=string]     [query_column=name]
       [separator=character]   [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -p
           Print only

       -s
           Only print SQL statements

       -c
           Print also totals for option length, area, or count

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       map=name [required]
           Name of vector map
           Or data source for direct OGR access

       layer=string
           Layer number or name (write to)
           Vector features can have category values in different layers. This  number  determines
           which layer to use. When used with direct OGR access this is the layer name.
           Default: 1

       type=string[,string,...]
           Feature type
           For coor valid point/centroid, for length valid line/boundary
           Options: point, line, boundary, centroid
           Default: point,line,boundary,centroid

       option=string [required]
           Value to upload
           Options:  cat,  area,  compact, fd, perimeter, length, count, coor, start, end, sides,
           query, slope, sinuous, azimuth, bbox
           cat: insert new row for each category if doesn’t exist yet
           area: area size
           compact: compactness of an area, calculated as
           compactness = perimeter / (2 * sqrt(PI * area))
           fd: fractal dimension of boundary defining a polygon, calculated as
           fd = 2 * (log(perimeter) / log(area))
           perimeter: perimeter length of an area
           length: line length
           count: number of features for each category
           coor: point coordinates, X,Y or X,Y,Z
           start: line/boundary starting point coordinates, X,Y or X,Y,Z
           end: line/boundary end point coordinates, X,Y or X,Y,Z
           sides: categories of areas on the left and right side of the  boundary,  ’query_layer’
           is used for area category
           query:  result of a database query for all records of the geometry(or geometries) from
           table specified by ’query_layer’ option
           slope: slope steepness of vector line or boundary
           sinuous: line sinuousity, calculated as line length / distance between end points
           azimuth: line azimuth,  calculated  as  angle  between  North  direction  and  endnode
           direction at startnode
           bbox: bounding box of area, N,S,E,W

       columns=name[,name,...] [required]
           Name of attribute column(s) to populate
           Name of attribute column(s)

       units=string
           Units
           Options: miles, feet, meters, kilometers, acres, hectares, radians, degrees

       query_layer=string
           Query layer number or name (read from)
           Vector  features  can have category values in different layers. This number determines
           which layer to use. When used with direct OGR access this is the layer name.
           Default: 1

       query_column=name
           Name of attribute column used for ’query’ option
           E.g. ’cat’, ’count(*)’, ’sum(val)’

       separator=character
           Field separator for print mode
           Special characters: pipe, comma, space, tab, newline
           Default: pipe

DESCRIPTION

       v.to.db loads vector map features or metrics into a database table, or prints them (or the
       SQL   queries   used   to  obtain  them)  in  a  form  of  a  human-readable  report.  For
       uploaded/printed category values ’-1’ is used for ’no category’ and ’null’/’-’ if category
       cannot  be  found  or  multiple  categories were found. For line azimuths ’-1’ is used for
       closed lines (start equals end).

NOTES

       Measures of lengths and areas are always reported in meters, unless the unit parameter  is
       set.  The units miles, feet, meters and kilometers are square for option=area.

       Feet  and  acre units are always reported in their common versions (i.e. the International
       Foot, exactly 5280 feet in a mile), even when the location’s standard map unit is  the  US
       Survey foot.

       When calculating perimeters in Latitude-Longitude locations, the geodesic distance between
       the vertices is used.

       When using option=coor on a vector area map, only coordinates  of  centroids  with  unique
       category will be reported.

       When using option=bbox on a vector area map with more than one feature per category value,
       the results corresponds to the bounding  box  of  all  features  of  same  category  taken
       together.

       Line azimuth is calculated as angle from the North direction to the line endnode direction
       at the line statnode. By default it’s reported in decimal degrees (0-360, CW) but it  also
       may  be  repored  in  radians with unit=radians. Azimuth value -1 is used to report closed
       line with it’s startnode and endnode being in same place. Azimuth values make  sense  only
       if every vector line has only one entry in database (unique CAT value).

       If  the  module  is  apparently slow and the map attributes are stored in an external DBMS
       such as PostgreSQL, it is highly recommended to create an  index  on  the  key  (category)
       column.

       Uploading  the  vector  map  attributes to a database requires a table attached to a given
       input vector layer. The print only (-p) mode doesn’t require a table.  Use  db.execute  or
       v.db.addtable to create a table if needed.

       Updating  the  table  has to be done column-wise. The column must be present in the table,
       except when using the print only (-p) mode. Use db.execute or v.db.addcolumn  to  add  new
       columns if needed.

EXAMPLES

   Updating attribute tables
       Upload category numbers to attribute table (used for new map):
       v.to.db map=soils type=centroid option=cat

       Upload polygon areas to corresponding centroid record in the attribute table:
       v.to.db map=soils type=centroid option=area columns=area_size unit=h

       Upload  line lengths (in meters) of each vector line to attribute table (use v.category in
       case of missing categories):
       v.to.db map=roads option=length type=line columns=linelength units=me

       Upload x and y coordinates from vector geometry to attribute table:
       v.to.db map=pointsmap option=coor columns=x,y

       Upload x, y and z coordinates from vector geometry to attribute table:
       v.to.db map=pointsmap option=coor columns=x,y,z

       Transfer attributes from a character column (with  numeric  contents)  to  a  new  integer
       column:
       v.db.addcolumn usa_income_employment2002 col="FIPS_NUM integer"
       v.to.db usa_income_employment2002 option=query columns=FIPS_NUM query_column=STATE_FIPS

       Upload category numbers of left and right area, to an attribute table of boundaries common
       for the areas:
       # add categories for boundaries of the input vector map, in layer 2:
       v.category soils out=mysoils layer=2 type=boundary option=add
       # add a table with columns named "left" and "right" to layer 2 of the input
       # vector map:
       v.db.addtable mysoils layer=2 columns="left integer,right integer"
       # upload categories of left and right areas:
       v.to.db mysoils option=sides columns=left,right layer=2
       # display the result:
       v.db.select mysoils layer=2

       Compute DL, the Fractal Dimension (Mandelbrot, 1982), of the boundary defining  a  polygon
       based on the formula:
       D = 2 * (log perimeter) / (log area):
       g.copy vect=soils,mysoils
       v.db.addcolumn mysoils col="d double precision"
       v.to.db mysoils option=fd column="d"
       g.region vector=mysoils res=50
       v.to.rast input=mysoils output=soils_fd type=area use=attr attribute_column=d
       r.colors map=soils_fd color=gyr
       d.mon wx0
       d.rast.leg soils_fd
       d.vect mysoils type=boundary

   Printing reports
       Report x,y,z coordinates of points in the input vector map:
       v.to.db -p bugsites option=coor type=point
       Report all area sizes of the input vector map:
       v.to.db -p soils option=area type=boundary units=h

       Report  all  area  sizes  of  the input vector map, in hectares, sorted by category number
       (requires GNU sort utility installed):
       v.to.db -p soils option=area type=boundary units=h | sort -n

       Report all line lengths of the input vector map, in kilometers:
       v.to.db -p roads option=length type=line units=k

       Report number of features for each category in the input vector map:
       v.to.db -p roads option=count type=line

SEE ALSO

         d.what.vect,  db.execute,  v.category,  v.db.addtable,   v.db.addcolumn,   v.db.connect,
       v.distance, v.report, v.univar, v.what

REFERENCES

           ·   Mandelbrot, B. B. (1982). The fractal geometry of nature. New York: W. H. Freeman.

           ·   Xu, Y. F. & Sun, D. A. (2005). Geotechnique 55, No. 9, 691-695

AUTHOR

       Radim Blazek, ITC-irst, Trento, Italy
       Line sinuousity implemented by Wolf Bergenheim

       Last changed: $Date: 2017-01-29 15:04:26 +0100 (Sun, 29 Jan 2017) $

SOURCE CODE

       Available at: v.to.db source code (history)

       Main index | Vector index | Topics index | Keywords index | Graphical index | Full index

       © 2003-2019 GRASS Development Team, GRASS GIS 7.6.1 Reference Manual