utmZone static method

ProjectionAdapter utmZone(UtmZone zone, { CoordRefSys? targetCrs, Datum? targetDatum, })

A projection adapter between WGS84 geographic and UTM projected positions.

Use forward of the adapter to return a projection for:

• source: lon and lat geographic coordinates (WGS 84)
• target: easting and northing UTM projected coordinates in the given zone (UTM/WGS 84 or UTM in the target datum if specified)

Use inverse of the adapter to return a projection for:

• source: easting and northing UTM projected coordinates in the given zone (UTM/WGS 84 or UTM in the target datum if specified)
• target: lon and lat geographic coordinates (WGS 84)

By default both source and target are based on the WGS 84 datum. If different datum is needed for the target, then specify it with both targetCrs and targetDatum (both must be non-null then).

Projected UTM positions are based on the WGS 84 ellipsoidal datum. Positions locate inside on of the 60 UTM zones (1-60) and in one of the two hemispheres (north or south). The zone is determined by the longitude and the hemisphere by the latitude of the position.

It's possible to specify the zone and the hemisphere so that the source position is not actually inside the zone. In such case projected coordinates may contain strange values.

You can also use the Utm class from the geodesy sub package to convert between geographic and UTM projected coordinates. This also allows converting from a geographic position to a UTM position with the zone and the hemisphere determined by that position without setting them. It also supports accessing metadata like the convergence and the scale factor related to the UTM projection.

With UtmZone.fromGeographic it's possible to calculate the UTM zone and the hemisphere for a geographic position.

The accuracy on conversions using other than the Datum.WGS84 datum is not guaranteed. The accuracy depends on the transformation parameter of the Helmert 7-parameter transformation used in the conversion.

Implementation

static ProjectionAdapter utmZone(
  UtmZone zone, {
  CoordRefSys? targetCrs,
  Datum? targetDatum,
}) {
  final isNonWGS84Target = targetCrs != null && targetDatum != null;
  return UtmProjectionAdapter.geographicToProjected(
    // source is geographic coordinates in WGS 84
    sourceCrs: CoordRefSys.CRS84,
    sourceDatum: Datum.WGS84,

    // target is UTM projected coordinates of the target zone in WGS 84 or the
    // given target datum
    targetCrs: isNonWGS84Target
        ? targetCrs
        : CoordRefSys.utmWgs84(zone.lonZone, zone.hemisphere),
    targetDatum: isNonWGS84Target ? targetDatum : Datum.WGS84,
    targetZone: zone,
  );
}