| Original File |
vecparam.htm |
| Abstract |
This web page sumarizes the GIServer query parameters created to enhace the interactivity with
the Web Map Server for Vectorial Data.
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| Author | Pedro Pereira Gonçalves (email) |
| Last Change |
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| History |
2002-03-04 : File Created
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| Index Page | GIServer tutorial |
| Important Links: |
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Apart from WMS parameters and general vectorial parameters, the GIServer accepts layer-specific query parameters. These parameters enhance the interactivity of the requests and give a direct linkage to the GIS data producing new dynamic layers of geographic informatio.
Note : When requesting these parameters it is necessary to specify to which layer are they refering. For example,
if the request is to drawn a borders layer with a PEN width of 2 pixels, it is necessary to specify :
<dataset>.<layer>.PEN = 2
Even if the GIServer parameters do NOT respect the WMS specification, all these non-WMS conformant
parameters might be transformed in to style definition
(see Styles and GIServer Parameters)
For querying vectorial data the following parameters are defined:
- .query
This string parameter will execute a query to the associated database in the vectorial file and will only draw the records resulting from that query.
It accepts the following mathematical operations: TRUNC, ROUND, ABS, ARCTAN, COS, EXP, FRAC, INT,
LN, PI, SIN, SQR, SQRT, POWER. In relation to strings it accepts the following functions: UPPER, LOWER, COPY, POS, LENGTH. Bitwise operations are also valid.
- .selectquery
This string parameter will execute a query to the associated database in the vectorial file and will draw the records resulting from that query like they were selected (with a pen width of 3 and red color).
It accepts the following mathematical operations: TRUNC, ROUND, ABS, ARCTAN, COS, EXP, FRAC, INT,
LN, PI, SIN, SQR, SQRT, POWER. In relation to strings it accepts the following functions: UPPER, LOWER, COPY, POS, LENGTH. Bitwise operations are also valid.
- .colorquery
This string parameter will execute a query to the associated database in the vectorial file and will only draw the records resulting from that query.
It accepts the following mathematical operations: TRUNC, ROUND, ABS, ARCTAN, COS, EXP, FRAC, INT,
LN, PI, SIN, SQR, SQRT, POWER. In relation to strings it accepts the following functions: UPPER, LOWER, COPY, POS, LENGTH. Bitwise operations are also valid.
This parameter can have multiple values present in the query to process multiple queries.For instance the query
TERRA.BORDERS.COLORQUERY=((UPPER(NAME)<>'ITALY'),0xFF0000) &
TERRA.BORDERS.COLORQUERY=((UPPER(NAME)='ITALY'),0x0000FF)
will paint Italy in blue and the rest of the world in red.
An additional parameter can be added to the query to indicate the text for the legend.
TERRA.BORDERS.COLORQUERY=((UPPER(NAME)<>'ITALY'),0xFF0000,Italy) &
When this parameter is omitted the legend will use the query text. If we add to previous request :
TERRA.BORDERS.COLORQUERY=((UPPER(NAME)<>'ITALY'),0xFF0000) &
TERRA.BORDERS.COLORQUERY=((UPPER(NAME)='ITALY'),0x0000FF,Italy) &
TERRA.BORDERS.LEGEND=TRUE
A legend will be added to the request displaying the text 'Italy' for the blue and
(UPPER(NAME)<>'ITALY') for the red.
(For more information about legend go to Legend parameters)
To access this queries from a file you can use the tag COLORQUERYFILE that must represent a file name without the extension placed in the same directory of the data file. The file format is just a sequency of colorquery values in each line. Something like
(COUNT=0,0xFEF1B4, )
(COUNT>0,0xFFCF00, 1 - 10 )
(COUNT>10,0xEBB400, 11 - 50)
(COUNT>50,0xB87100, 51 - 100)
(COUNT>100,0x8D3700, 101 - 200)
(COUNT>200,0x630000, mais de 200)
and it should be saved with the extension '.query'. Please note that if this text file is dynamically changed by some other process you should warn the cache system.
It is also possible to generate automatic color distribution using the AUTO function. It this function you have to select a numeric field and the GIServer will automatically create the palette going from the minimum color value to maximum color value with the number of classes specified. The syntax is :
COLORQUERY = AUTO(<TYPE>, <FIELD>, <MINCLASSCOLOR>, <MAXCLASSCOLOR>, <NUMCLASS>, [<SPECIFICVALUE>,<SPECIFICCOLOR>, .... ])
EXAMPLE:
&TERRA.BORDERS.LEGEND.X=-2&TERRA.BORDERS.MAXVALUE=500&TERRA.BORDERS.FIELD=COUNT)
REQUEST=GETMAP&
LAYERS=TERRA.BORDERS&
BBOX=-10,30,70,70&
SRS=EPSG:4326&
WIDTH=300&
HEIGHT=150&
FORMAT=GIF&
TERRA.BORDERS.LEGEND.X=-2&
TERRA.BORDERS.MAXVALUE=500&
TERRA.BORDERS.FIELD=COUNT&
TERRA.BORDERS.COLORQUERY=AUTO(DEC,COUNT,0x630000,0xFFCF00,5,0,0xFFF1AD)
note: Possible values for TYPE are DEC, MULT2, MULT3, MULT4 ...
See also:
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