UnitReference¶

class geodetic_engine.persistablereference.UnitReference[source]¶

Bases: Reference

A unit, stated by how it converts to its SI base.

USO states a scale and an offset, UAD a rational polynomial. The polynomial reduces to a scale and an offset whenever its d term is zero, which is the usual case.

symbol¶: The unit’s symbol, for example "ft".

measurement¶: What it measures, for example "length", or "".

coefficients¶: The polynomial (a, b, c, d) in si = (a + b * value) / (c + d * value). A scale and offset is held as (offset, scale, 1, 0), which is the same conversion.

property scale: float¶

The conversion’s scale factor.

Raises:: UnsupportedReferenceError – If the conversion is not linear, and so has no single scale.

property offset: float¶

The conversion’s offset, in the SI base unit.

Raises:: UnsupportedReferenceError – If the conversion is not linear.

to_si(value)[source]¶

Convert a value in this unit to the SI base unit.

Parameters:: value (float) – The value to convert.
Return type:: float
Returns:: The value in the SI base unit.
Raises:: MalformedReferenceError – If the conversion is undefined at this value.

from_si(value)[source]¶

Convert a value in the SI base unit to this unit.

Parameters:: value (float) – The value in the SI base unit.
Return type:: float
Returns:: The value in this unit.
Raises:: MalformedReferenceError – If the conversion cannot be inverted at this value.

convert_to(other, value)[source]¶

Convert a value from this unit to another.

Parameters:

other (UnitReference) – The unit to convert to, which must measure the same thing.
value (float) – The value in this unit.

Return type:

float

Returns:

The value in other.

Raises:

MalformedReferenceError – If either conversion is undefined at this value.
UnsupportedReferenceError – If the two units measure different things, where a conversion would be meaningless.

__init__(raw, kind, name, authority_code, version, symbol, measurement, coefficients)¶