.TH v.to.db 1grass "" "GRASS 7.8.5" "GRASS GIS User's Manual"
.SH NAME
\fI\fBv.to.db\fR\fR  \- Populates attribute values from vector features.
.SH KEYWORDS
vector, attribute table, database, area, azimuth, bounding box, category, compactness, coordinates, fractal, geometry, length, perimeter, sides, sinuous, slope
.SH SYNOPSIS
\fBv.to.db\fR
.br
\fBv.to.db \-\-help\fR
.br
\fBv.to.db\fR [\-\fBpsc\fR] \fBmap\fR=\fIname\fR  [\fBlayer\fR=\fIstring\fR]   [\fBtype\fR=\fIstring\fR[,\fIstring\fR,...]]  \fBoption\fR=\fIstring\fR \fBcolumns\fR=\fIname\fR[,\fIname\fR,...]  [\fBunits\fR=\fIstring\fR]   [\fBquery_layer\fR=\fIstring\fR]   [\fBquery_column\fR=\fIname\fR]   [\fBseparator\fR=\fIcharacter\fR]   [\-\-\fBoverwrite\fR]  [\-\-\fBhelp\fR]  [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR]  [\-\-\fBui\fR]
.SS Flags:
.IP "\fB\-p\fR" 4m
.br
Print only
.IP "\fB\-s\fR" 4m
.br
Only print SQL statements
.IP "\fB\-c\fR" 4m
.br
Print also totals for option length, area, or count
.IP "\fB\-\-overwrite\fR" 4m
.br
Allow output files to overwrite existing files
.IP "\fB\-\-help\fR" 4m
.br
Print usage summary
.IP "\fB\-\-verbose\fR" 4m
.br
Verbose module output
.IP "\fB\-\-quiet\fR" 4m
.br
Quiet module output
.IP "\fB\-\-ui\fR" 4m
.br
Force launching GUI dialog
.SS Parameters:
.IP "\fBmap\fR=\fIname\fR \fB[required]\fR" 4m
.br
Name of vector map
.br
Or data source for direct OGR access
.IP "\fBlayer\fR=\fIstring\fR" 4m
.br
Layer number or name (write to)
.br
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.
.br
Default: \fI1\fR
.IP "\fBtype\fR=\fIstring[,\fIstring\fR,...]\fR" 4m
.br
Feature type
.br
For coor valid point/centroid, for length valid line/boundary
.br
Options: \fIpoint, line, boundary, centroid\fR
.br
Default: \fIpoint,line,boundary,centroid\fR
.IP "\fBoption\fR=\fIstring\fR \fB[required]\fR" 4m
.br
Value to upload
.br
Options: \fIcat, area, compact, fd, perimeter, length, count, coor, start, end, sides, query, slope, sinuous, azimuth, bbox\fR
.br
\fBcat\fR: insert new row for each category if doesn\(cqt exist yet
.br
\fBarea\fR: area size
.br
\fBcompact\fR: compactness of an area, calculated as
.br
compactness = perimeter / (2 * sqrt(PI * area))
.br
\fBfd\fR: fractal dimension of boundary defining a polygon, calculated as
.br
fd = 2 * (log(perimeter) / log(area))
.br
\fBperimeter\fR: perimeter length of an area
.br
\fBlength\fR: line length
.br
\fBcount\fR: number of features for each category
.br
\fBcoor\fR: point coordinates, X,Y or X,Y,Z
.br
\fBstart\fR: line/boundary starting point coordinates, X,Y or X,Y,Z
.br
\fBend\fR: line/boundary end point coordinates, X,Y or X,Y,Z
.br
\fBsides\fR: categories of areas on the left and right side of the boundary, \(cqquery_layer\(cq is used for area category
.br
\fBquery\fR: result of a database query for all records of the geometry(or geometries) from table specified by \(cqquery_layer\(cq option
.br
\fBslope\fR: slope steepness of vector line or boundary
.br
\fBsinuous\fR: line sinuousity, calculated as line length / distance between end points
.br
\fBazimuth\fR: line azimuth, calculated as angle between North direction and endnode direction at startnode
.br
\fBbbox\fR: bounding box of area, N,S,E,W
.IP "\fBcolumns\fR=\fIname[,\fIname\fR,...]\fR \fB[required]\fR" 4m
.br
Name of attribute column(s) to populate
.br
Name of attribute column(s)
.IP "\fBunits\fR=\fIstring\fR" 4m
.br
Units
.br
Options: \fImiles, feet, meters, kilometers, acres, hectares, radians, degrees\fR
.IP "\fBquery_layer\fR=\fIstring\fR" 4m
.br
Query layer number or name (read from)
.br
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.
.br
Default: \fI1\fR
.IP "\fBquery_column\fR=\fIname\fR" 4m
.br
Name of attribute column used for \(cqquery\(cq option
.br
E.g. \(cqcat\(cq, \(cqcount(*)\(cq, \(cqsum(val)\(cq
.IP "\fBseparator\fR=\fIcharacter\fR" 4m
.br
Field separator for print mode
.br
Special characters: pipe, comma, space, tab, newline
.br
Default: \fIpipe\fR
.SH DESCRIPTION
\fIv.to.db\fR 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
\(cq\-1\(cq is used for \(cqno category\(cq and \(cqnull\(cq/\(cq\-\(cq if category cannot be
found or multiple categories were found. For line azimuths \(cq\-1\(cq is used
for closed lines (start equals end).
.SH NOTES
Measures of lengths and areas are always reported in meters, unless the
\fIunit\fR parameter is set.
The units \fImiles\fR, \fIfeet\fR, \fImeters\fR and
\fIkilometers\fR are square for \fIoption=area\fR.
.PP
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\(cqs standard map unit is the US Survey foot.
.PP
When calculating perimeters in Latitude\-Longitude locations, the geodesic
distance between the vertices is used.
.PP
When using \fIoption=coor\fR on a vector area map,
only coordinates of centroids with unique category will be reported.
.PP
When using \fIoption=bbox\fR 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.
.PP
Line azimuth is calculated as angle from the North direction to the line endnode
direction at the line statnode. By default it\(cqs reported in decimal degrees (0\-360, CW) but
it also may be repored in radians with \fIunit=radians\fR. Azimuth value
\fB\-1\fR is used to report closed line with it\(cqs 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).
.PP
If the module is apparently slow \fIand\fR 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.
.PP
Uploading the vector map attributes to a database requires a table attached to
a given input vector \fIlayer\fR. The \fBprint only\fR (\fB\-p\fR) mode
doesn\(cqt require a table. Use \fIdb.execute\fR
or \fIv.db.addtable\fR to create a table if
needed.
.PP
Updating the table has to be done column\-wise. The \fIcolumn\fR will be
created in the table if it doesn\(cqt already exist, except when using the
\fBprint only\fR (\fB\-p\fR) mode. If the \fIcolumn\fR exists, the
\fB\-\-overwrite\fR flag is required to overwrite it.
.SH EXAMPLES
.SS Updating attribute tables
Upload category numbers to attribute table (used for new map):
.br
.br
.nf
\fC
v.to.db map=soils type=centroid option=cat
\fR
.fi
.PP
Upload polygon areas to corresponding centroid record in the attribute table:
.br
.br
.nf
\fC
v.to.db map=soils type=centroid option=area columns=area_size unit=h
\fR
.fi
.PP
Upload line lengths (in meters) of each vector line to attribute table
(use \fIv.category\fR in case of missing categories):
.br
.br
.nf
\fC
v.to.db map=roads option=length type=line columns=linelength units=me
\fR
.fi
.PP
Upload x and y coordinates from vector geometry to attribute table:
.br
.br
.nf
\fC
v.to.db map=pointsmap option=coor columns=x,y
\fR
.fi
.PP
Upload x, y and z coordinates from vector geometry to attribute table:
.br
.br
.nf
\fC
v.to.db map=pointsmap option=coor columns=x,y,z
\fR
.fi
.PP
Transfer attributes from a character column (with numeric contents) to a new
integer column:
.br
.br
.nf
\fC
v.db.addcolumn usa_income_employment2002 col=\(dqFIPS_NUM integer\(dq
v.to.db usa_income_employment2002 option=query columns=FIPS_NUM query_column=STATE_FIPS
\fR
.fi
.PP
Upload category numbers of left and right area, to an attribute table of
boundaries common for the areas:
.br
.br
.nf
\fC
# 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 \(dqleft\(dq and \(dqright\(dq to layer 2 of the input
# vector map:
v.db.addtable mysoils layer=2 columns=\(dqleft integer,right integer\(dq
# 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
\fR
.fi
.PP
Compute DL, the Fractal Dimension (Mandelbrot, 1982), of the
boundary defining a polygon based on the formula:
.br
D = 2 * (log perimeter) / (log area):
.br
.br
.nf
\fC
g.copy vect=soils,mysoils
v.db.addcolumn mysoils col=\(dqd double precision\(dq
v.to.db mysoils option=fd column=\(dqd\(dq
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
\fR
.fi
.SS Printing reports
Report x,y,z coordinates of points in the input vector map:
.br
.br
.nf
\fC
v.to.db \-p bugsites option=coor type=point
\fR
.fi
Report all area sizes of the input vector map:
.br
.br
.nf
\fC
v.to.db \-p soils option=area type=boundary units=h
\fR
.fi
.PP
Report all area sizes of the input vector map, in hectares, sorted by category
number (requires GNU \fIsort\fR utility installed):
.br
.br
.nf
\fC
v.to.db \-p soils option=area type=boundary units=h | sort \-n
\fR
.fi
.PP
Report all line lengths of the input vector map, in kilometers:
.br
.br
.nf
\fC
v.to.db \-p roads option=length type=line units=k
\fR
.fi
.PP
Report number of features for each category in the input vector map:
.br
.br
.nf
\fC
v.to.db \-p roads option=count type=line
\fR
.fi
.SH SEE ALSO
\fI
d.what.vect,
db.execute,
v.category,
v.db.addtable,
v.db.addcolumn,
v.db.connect,
v.distance,
v.report,
v.univar,
v.what
\fR
.SH REFERENCES
.RS 4n
.IP \(bu 4n
Mandelbrot, B. B. (1982). The fractal geometry of nature. New York: W. H. Freeman.
.IP \(bu 4n
Xu, Y. F. & Sun, D. A. (2005). Geotechnique 55, No. 9, 691\-695
.RE
.SH AUTHOR
Radim Blazek, ITC\-irst, Trento, Italy
.br
Line sinuousity implemented by Wolf Bergenheim
.SH SOURCE CODE
.PP
Available at: v.to.db source code (history)
.PP
Main index |
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Keywords index |
Graphical index |
Full index
.PP
© 2003\-2020
GRASS Development Team,
GRASS GIS 7.8.5 Reference Manual