Provided by: grass-doc_7.4.0-1_all bug

NAME

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

KEYWORDS

       vector, attribute table, database

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

       © 2003-2018 GRASS Development Team, GRASS GIS 7.4.0 Reference Manual