# Fields that are within a Specified Distance from a Specified Point

## DISTCARTESIAN

The `DISTCARTESIAN` field specifier allows you to find documents that contain fields that define a point (X and Y coordinates) or region that is within a specified distance from a specified point.

You can specify the document position fields either as a pair of fields (corresponding to X and Y coordinate fields), or a single field that uses POINT or POLYGON definitions (in Well-known text format) to specify position information (for example, a unified `GeospatialType` field).

TIP: If your document location fields contain regions (in Well-known text POLYGON format), the `DISTCARTESIAN` operator calculates distances from the geometric center of the region.

    FieldText=DISTCARTESIAN{coordX,coordY,dist}:POSITION

where:

`coordX` | is the specified X coordinate.
`coordY` | is the specified Y coordinate.
`dist` | is the distance in kilometers from the specified coordinates.
`POSITION` | The document field or fields that contain the position value. You can use one of the following options to specify location fields: a single field. This field must contain a Well-known text format POINT or POLYGON definition (for example, `POINT(x y)`). two fields, in the format `X:Y`, where `X` is the field that contains the x coordinate, and `Y` is the field that contains the y coordinate. You must specify the fields in the order `x:y`. You can specify multiple options for the location fields, in form `POSITION1:POSITION2:POSITION3`, and so on. This form can include a mix of types (unified location fields and split latitude and longitude fields). NOTE: If you use multiple position fields or field pairs, IDOL Server cannot match documents where a pair of split geospatial fields occurs interleaved with other geospatial fields. For example, if you use `X1:Y1:POSITION` in your query, and these fields occur in a document in the order `X1`, `POSITION`, `Y1`, IDOL Server does not match that document. In such cases, you can rewrite the query, in the form `DISTCARTESIAN{...}:X1:Y1 OR DISTCARTESIAN{...}:POSITION`

Example:

    FieldText=DISTCARTESIAN{10,11,5}:X:Y

This example matches all documents whose (X,Y) position is within a distance of 5 units of the point (10,11). The position of a document in this example is contained in the fields `X` and `Y`.

    FieldText=DISTCARTESIAN{10,11,5}:POSITION

This example matches all documents whose (X,Y) position is within a distance of 5 units of the point (10,11). The position of a document in this example is contained in the `POSITION` field.

## DISTSPHERICAL

The `DISTSPHERICAL` field specifier allows you to find documents that contain location fields that define a point (latitude and longitude) or region that is within a specified distance from a specified point.

You can specify the document location fields either as a pair of fields (corresponding to latitude and longitude fields), or a single field that uses POINT or POLYGON definitions (in Well-known text format) to specify location information (for example, a unified `GeospatialType` field).

TIP: If your document location fields contain regions (in Well-known text POLYGON format), the `DISTSPHERICAL` operator calculates distances from the geometric center of the region.

    FieldText=DISTSPHERICAL{lat,long,dist}:LOCATION

where:

`lat` | is the latitude. Specify latitude positions south of the equator as negative.
`long` | is the longitude. Specify longitude positions west of the Greenwich Meridian as negative.
`dist` | is the distance in kilometers from the specified latitude and longitude.
`LOCATION` | The document field or fields that contain the location value. You can use one of the following options to specify location fields: a single field. This field must contain a Well-known text format POINT definition (that is, `POINT (x y)`). two fields, in the format `LATFIELD:LONGFIELD`, where `LATFIELD` is the field that contains the latitude value, and `LONGFIELD` is the field that contains the longitude value. You must specify the fields in the order `latitude:longitude`. You can specify multiple options for the location fields, in form `LOCATION1:LOCATION2:LOCATION3`, and so on. This form can include a mix of types (unified location fields and split latitude and longitude fields). NOTE: If you use multiple position fields or field pairs, IDOL Server cannot match documents where a pair of split geospatial fields occurs interleaved with other geospatial fields. For example, if you use `LAT1:LONG1:LOCATION` in your query, and these fields occur in a document in the order `LAT1`, `LOCATION`, `LONG1`, IDOL Server does not match that document. In such cases, you can rewrite the query, in the form `DISTSPHERICAL{...}:LAT1:LONG1 OR DISTCARTESIAN{...}:LOCATION`

Example:

    FieldText=DISTSPHERICAL{37.75,-122.4,20}:LAT:LONG

This example matches all documents whose position is within a 20 kilometer radius of San Francisco (37.75N,122.4W). The latitude and longitude position of a document in this example is contained in the fields `LAT` and `LONG`, respectively.

    FieldText=DISTSPHERICAL{52.2,0.1,20}:LOCATION

This example matches all documents whose position is within a 20 kilometer radius of Cambridge (52.2N,0.1W). The latitude and longitude position of a document in this example is contained in the `LOCATION` field.

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