Library upgrade assistance about phpcoord HOT 3 CLOSED

Yes, the original versions were very OSGB36 specific and kinda sorta ignored a lot of (sadly needed) complexity that's required once you expand to different coordinate systems.

//Old
$os = new OSRef(199800, 554200);
//New
$from = ProjectedPoint::createFromEastingNorthing(
new Metre(554200),
new Metre(199800),
Projected::fromSRID(Projected::EPSG_OSGB_1936_BRITISH_NATIONAL_GRID)
);

This looks right, except that you've reversed the order of coordinates - both old and new are (easting, northing) so you shouldn't need to do that.

From there, you need to explicitly decide which "world model" (datum/ellipsoid) you want your latitude and longitude to use. The older version you're currently using would have assumed you wanted the Airy Ellipsoid (OSGB36). If you actually wanted WGS84 instead, you'd do a followup conversion. Those were the only 2 coordinate systems it supported so that made it easy to use.

//Old
$ll = $os->toLatLng(); // assumed OSGB36/Airy Ellipsoid
$ll->OSGB36ToWGS84(); // optional conversion depending on needs

New PHPCoord allows you to convert to many, many different systems so you need to choose up front.

//New
$toCRS = Geographic2D::fromSRID(Geographic2D::EPSG_OSGB_1936);
//or
$toCRS = Geographic2D::fromSRID(Geographic2D::EPSG_WGS_84);
$to = $from->convert($toCRS);
echo $to->getLatitude() . " " . $to->getLongitude();

Hope that helps?

from phpcoord.

See also https://www.phpcoord.net/en/stable/creating_points_projected.html#british-national-grid if you need to work with grid letters

from phpcoord.

Cheers for your help Doug - with your kind notes and a fresh head this morning I was able to tackle it.

You were correct - I was converting a grid ref to Easting & Northings prior to that step as I don't think the library supported that at the time. I've removed that step now.

Here's my final code in case it helps anyone.

$point = BritishNationalGridPoint::fromGridReference('TQ 30017 80419');
$toCRS = Geographic2D::fromSRID(Geographic2D::EPSG_OSGB_1936);
$to = $point->convert($toCRS);
$start_lat = floatval((string) $to->getLatitude());
$start_lng = floatval((string) $to->getLongitude());

Thanks again.

from phpcoord.