# gml:ConversionToPreferredUnitType

The inherited attribute uom references the preferred unit that this conversion applies to. The conversion of a unit to the preferred unit for this physical quantity type is specified by an arithmetic conversion (scaling and/or offset). The content model extends gml:UnitOfMeasureType, which has a mandatory attribute uom which identifies the preferred unit for the physical quantity type that this conversion applies to. The conversion is specified by a choice of - gml:factor, which defines the scale factor, or - gml:formula, which defines a formula by which a value using the conventional unit of measure can be converted to obtain the corresponding value using the preferred unit of measure. The formula defines the parameters of a simple formula by which a value using the conventional unit of measure can be converted to the corresponding value using the preferred unit of measure. The formula element contains elements a, b, c and d, whose values use the XML Schema type double. These values are used in the formula y = (a + bx) / (c + dx), where x is a value using this unit, and y is the corresponding value using the base unit. The elements a and d are optional, and if values are not provided, those parameters are considered to be zero. If values are not provided for both a and d, the formula is equivalent to a fraction with numerator and denominator parameters.

## Complex type information

Namespace: http://www.opengis.net/gml/3.2

Schema document: external/ogc/gml/3.2.1/units.xsd

## Content

- Choice [1..1]

## Attributes

Name | Occ | Type | Description | Notes |
---|---|---|---|---|

uom | [1..1] | gml:UomIdentifier | from type gml:UnitOfMeasureType |

## Used by

- Element gml:conversionToPreferredUnit
- Element gml:roughConversionToPreferredUnit

## Type inheritance chain

- gml:UnitOfMeasureType
- gml:ConversionToPreferredUnitType