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v.to.db(1)		    GRASS GIS User's Manual		    v.to.db(1)

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

KEYWORDS
       vector,	attribute  table, database, area, azimuth, bounding box, cate-
       gory, compactness, coordinates, fractal,	geometry,  length,  perimeter,
       sides, sinuous, slope

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=nameA [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 ac-
	   cess	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=stringA [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	bound-
	   ary,	'query_layer' is used for area category
	   query: result of a database query for all  records  of  the	geome-
	   try(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 be-
	   tween 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,...]A	[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 ac-
	   cess	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 hu-
       man-readable report. For	uploaded/printed category values '-1' is  used
       for  'no	category' and 'null'/'-' if category cannot be found or	multi-
       ple 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 lo-
       cation's	standard map unit is the US Survey foot.

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

       When using option=coor on a vector area map, only coordinates  of  cen-
       troids 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 at-
       tached 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 will be  cre-
       ated  in	 the  table if it doesn't already exist, except	when using the
       print only (-p) mode. If	the column exists, the --overwrite flag	is re-
       quired to overwrite it.

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

	   o   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

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

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

       A(C) 2003-2020 GRASS Development	Team, GRASS GIS	7.8.3 Reference	Manual

GRASS 7.8.3							    v.to.db(1)

NAME | KEYWORDS | SYNOPSIS | DESCRIPTION | NOTES | EXAMPLES | SEE ALSO | REFERENCES | AUTHOR | SOURCE CODE

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