Creating Geometry Objects From Features

You may want to use an existing feature as part of a spatial query. To retrieve the feature’s geometry and convert it into an appropriate format for a query, perform the following steps:

• Create a query that will select the feature.
• Query the feature class containing the feature using the MgFeatureService::SelectFeatures() method.
• Obtain the feature from the query using the MgFeatureReader::ReadNext() method.
• Get the geometry data from the feature using the MgFeatureReader::GetGeometry() method. This data is in AGF binary format.
• Convert the AGF data to an MgGeometry object using the MgAgfReaderWriter::Read() method.

For example, the following sequence creates an MgGeometry object representing the boundaries of District 1 in the Sheboygan sample data.

$districtQuery = new MgFeatureQueryOptions();
$districtQuery->SetFilter("Autogenerated_SDF_ID = 1");
 
$layer = $map->GetLayers()->GetItem('Districts');
$featureReader = $layer->SelectFeatures($districtQuery);
$featureReader->ReadNext();
$districtGeometryData = $featureReader->GetGeometry('Data');
$agfReaderWriter = new MgAgfReaderWriter();
$districtGeometry = $agfReaderWriter->Read($districtGeometryData);

To convert an MgGeometry object into its WKT representation, use the MgWktReaderWriter::Write() method, as in the following example:

$wktReaderWriter = new MgWktReaderWriter();
$districtWkt = $wktReaderWriter->Write($districtGeometry);