1v.to.db(1) Grass User's Manual v.to.db(1)
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6 v.to.db - Load values from vector to database. In uploaded/printed
7 category values '-1' is used for 'no category' and 'null'/'-' if cate‐
8 gory cannot be found or multiple categories were found.
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11 vector
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14 v.to.db
15 v.to.db help
16 v.to.db [-psc] map=name [type=string[,string,...]] [layer=integer]
17 [qlayer=integer] option=string [units=string] [col‐
18 umn=string[,string,...]] [qcolumn=string]
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20 Flags:
21 -p print only
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23 -s only print sql statements
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25 -c In print mode prints totals for options: length,area,count
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27 Parameters:
28 map=name
29 Name of input vector map
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31 type=string[,string,...]
32 Type of elements (for coor valid point/centroid, for length valid
33 line/boundary) Options: point,line,boundary,centroid Default:
34 point,line,boundary,centroid
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36 layer=integer
37 Layer number Default: 1
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39 qlayer=integer
40 Query layer. Used by 'query' option. Default: 1
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42 option=string
43 Value to upload Options: cat,area,compact,perime‐
44 ter,length,count,coor,start,end,sides,query cat: insert new row for
45 each category if doesn't exist yet area: area size compact: com‐
46 pactness of an area, calculated as compactness = perimeter / (2 *
47 sqrt(PI * area)) perimeter: perimeter length of an area length:
48 line length count: number of features for each category coor: point
49 coordinates, X,Y or X,Y,Z start: line/boundary starting point coor‐
50 dinates, X,Y or X,Y,Z end: line/boundary end point coordinates, X,Y
51 or X,Y,Z sides: categories of areas on the left and right side of
52 the boundary, 'qlayer' is used for area category query: result of a
53 database query for all records of the geometry(or geometries) from
54 table specified by 'qlayer' option
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56 units=string
57 mi(les),f(eet),me(ters),k(ilometers),a(cres),h(ectares) Options:
58 mi,miles,f,feet,me,meters,k,kilometers,a,acres,h,hectares
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60 column=string[,string,...]
61 column(s)
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63 qcolumn=string
64 Query column used for 'query' option. E.g. 'cat', 'count(*)',
65 'sum(val)'
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68 v.to.db loads vector map features or metrics into a database table, or
69 prints them (or the SQL queries used to obtain them) in a form of a
70 human-readable report.
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73 The units miles, feet, meters and kilometers are square for
74 option=area.
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76 When using option=coor on a vector area map, only coordinates of cen‐
77 troids with unique category will be reported.
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79 When calculating perimeters in Latitude-Longitude locations, the geo‐
80 desic distance between the vertices is used.
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82 If the module is apparently slow and the map attributes are stored in
83 an external DBMS such as PostgreSQL, it is highly recommended to create
84 an index on the key (category) column.
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86 Uploading the vector map attributes to a database requires a table
87 attached to a given input vector layer. The print only (-p) mode
88 doesn't require a table. Use db.execute or v.db.addtable to create a
89 table if needed.
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91 Updating the table has to be done column-wise. The column must be
92 present in the table, except when using the print only (-p) mode. Use
93 db.execute or v.db.addcol to add new columns if needed.
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96 Updating attribute tables
97 Upload category numbers to attribute table (used for new map):
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99 v.to.db map=soils type=area option=cat
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102 Upload area sizes of each polygon to attribute table:
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104 v.to.db map=soils type=area option=area col=area_size unit=h
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107 Upload line lengths (in meters) of each vector line to attribute table
108 (use v.category in case of missing categories):
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110 v.to.db map=roads option=length type=line col=linelength units=me
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113 Upload x and y coordinates from vector geometry to attribute table:
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115 v.to.db map=pointsmap option=coor col=x,y
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118 Upload x, y and z coordinates from vector geometry to attribute table:
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120 v.to.db map=pointsmap option=coor col=x,y,z
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123 Transfer of attributes from character column (with numeric contents) to
124 new integer column:
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126 v.db.addcol usa_income_employment2002 col="FIPS_NUM integer"
127 v.to.db usa_income_employment2002 option=query col=FIPS_NUM
128 qcol=STATE_FIPS
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131 Upload category numbers of left/right polygons neighboring boundaries
132 to attribute table:
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134 # add boundary categories into geometry at layer 2:
135 v.category soils out=mysoils layer=2 type=boundary option=add
136 # add table with left/right column to layer 2:
137 v.db.addtable mysoils layer=2 col="left integer,right integer"
138 # upload categories of left/right polygons:
139 v.to.db mysoils option=sides col=left,right layer=2
140 # display the result:
141 v.db.select mysoils layer=2
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144 Printing reports
145 Print x,y,z coordinates using dummy columns. The columns don't have to
146 exist in the table for the features to be reported. Even a table is not
147 required:
148 v.to.db -p bugsites option=coor type=point column=dummy1,dummy2
149 Report all area sizes of a map:
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151 v.to.db -p soils option=area type=boundary units=h
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154 Report all area sizes of a map, sorted by category number:
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156 v.to.db -p soils option=area type=boundary units=h | sort -n
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159 Report all line lengths of a map:
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161 v.to.db -p roads option=length type=line units=k
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164 Report number of features for each category in map:
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166 v.to.db -p roads option=count type=line
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170 v.category v.db.addtable v.db.addcol v.db.connect v.distance db.exe‐
171 cute v.what d.what.vect
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174 Radim Blazek
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176 Last changed: $Date: 2006/09/22 12:22:10 $
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178 Full index
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182GRASS 6.2.2 v.to.db(1)