NAME

KEYWORDS

SYNOPSIS

Flags:

-p

Print only

-s

Only print sql statements

-c

In print mode prints totals for options: length,area,count

--verbose

Verbose module output

--quiet

Quiet module output

Parameters:

map=name

Name of input vector map

type=string[,string,...]

Type of elements (for coor valid point/centroid, for length valid line/boundary)

Feature type(s)

Options: point,line,boundary,centroid

Default: point,line,boundary,centroid

layer=integer

Layer number

A single vector map can be connected to multiple database tables. This number determines which table to use.

Default: 1

qlayer=integer

Query layer (used by 'query' option)

A single vector map can be connected to multiple database tables. This number determines which table to use.

Default: 1

option=string

Value to upload

Options: cat,area,compact,fd,perimeter,length,count,coor,start,end,sides,query,slope,sinuous

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, 'qlayer' is used for area category

query: result of a database query for all records of the geometry(or geometries) from table specified by 'qlayer' option

slope: slope steepness of vector line or boundary

sinuous: line sinuousity, calculated as line length / distance between end points

units=string

Units

mi(les),f(eet),me(ters),k(ilometers),a(cres),h(ectares)

Options: mi,miles,f,feet,me,meters,k,kilometers,a,acres,h,hectares

columns=name[,name,...]

Name of attribute column(s)

qcolumn=name

Name of attribute column used for 'query' option

E.g. 'cat', 'count(*)', 'sum(val)'

DESCRIPTION

NOTES

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.

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.addcol to add new columns if needed.

EXAMPLES

Updating attribute tables

v.to.db map=soils type=area option=cat

Upload area sizes of each polygon to attribute table:

v.to.db map=soils type=area option=area col=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 col=linelength units=me

Upload x and y coordinates from vector geometry to attribute table:

v.to.db map=pointsmap option=coor col=x,y

Upload x, y and z coordinates from vector geometry to attribute table:

v.to.db map=pointsmap option=coor col=x,y,z

Transfer attributes from a character column (with numeric contents) to a new integer column:

v.db.addcol usa_income_employment2002 col="FIPS_NUM integer"
v.to.db usa_income_employment2002 option=query col=FIPS_NUM qcol=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 col="left integer,right integer"
# upload categories of left and right areas:
v.to.db mysoils option=sides col=left,right layer=2
# display the result:
v.db.select mysoils layer=2

Compute D_L, 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.addcol mysoils col="d double precision"
v.to.db mysoils option=fd column="d"

g.region vect=mysoils res=50
v.to.rast in=mysoils out=soils_fd type=area use=attr column=d
r.colors map=soils_fd color=gyr

d.mon x0
d.rast.leg soils_fd
d.vect mysoils type=boundary

Printing reports

v.to.db -p bugsites option=coor type=point

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

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

Last changed: $Date: 2008-01-13 05:35:14 -0800 (Sun, 13 Jan 2008) $

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