Enum ConversionMethod 

pub enum ConversionMethod {
    Ostn15,
    Proj,
}

Which backend to use when converting WGS84 coordinates to BNG.

When PROJ grid files are installed both methods agree to within ~1mm. The difference matters when grid files are absent:

Scenario	Proj	Ostn15
PROJ + grid files installed	~1mm	~1mm
PROJ installed, no grid files	~5m (silent!)	~1mm
PROJ not installed	build fails	~1mm

Ostn15 is the safer default for libraries — accuracy is guaranteed regardless of what the user has installed on their system.

Variants

Ostn15

Use the lonlat_bng crate with OSTN15 data embedded at compile time.

Always ~1mm accurate. No system dependencies.

Proj

Use the proj system library (equivalent to pyproj).

Requires libproj and the uk_os_OSTN15_NTv2_OSGBtoETRS.tif grid file. Without the grid file PROJ silently falls back to a ~5m Helmert transform.

Trait Implementations

impl Clone for ConversionMethod

fn clone(&self) -> ConversionMethod

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for ConversionMethod

impl Debug for ConversionMethod

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for ConversionMethod

fn default() -> ConversionMethod

Returns the “default value” for a type.

impl Eq for ConversionMethod

impl PartialEq for ConversionMethod

fn eq(&self, other: &ConversionMethod) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for ConversionMethod