Geometrievalidierung

Die Aspose.GIS API ermöglicht es Ihnen, Geometrien für eine Reihe von Operationen zu validieren. Sie bietet Ihnen die Möglichkeit, eine Geometrie auf Regeln bezüglich Geometrien sowie Spezifikationen von geospatialen Dateiformaten zu validieren.

Überprüfung der Geometrie auf Gültigkeit

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
LinearRing linearRing = new LinearRing();
linearRing.AddPoint(0, 0);
linearRing.AddPoint(0, 1);
linearRing.AddPoint(1, 0);
bool valid = linearRing.IsValid; // valid == false
linearRing.AddPoint(0, 0);
valid = linearRing.IsValid; // valid == true

Überprüfung der Geometrie auf Einfachheit

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
LineString lineString = new LineString();
bool simple = lineString.IsSimple; // simple == true
lineString.AddPoint(0, 0);
lineString.AddPoint(1, 0);
simple = lineString.IsSimple; // simple == true
lineString.AddPoint(0.5, 0);
simple = lineString.IsSimple; // simple == false (line string crosses itself)

Validierung von Geometrien beim Schreiben

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
var exteriorRing = new LinearRing();
exteriorRing.AddPoint(0, 0);
exteriorRing.AddPoint(0, 1);
exteriorRing.AddPoint(1, 1);
exteriorRing.AddPoint(1, 0);
exteriorRing.AddPoint(0, 0);

var interiorRing = new LinearRing();
interiorRing.AddPoint(0.5, 0.5);
interiorRing.AddPoint(1, 0.5);
interiorRing.AddPoint(1, 1);
interiorRing.AddPoint(0.5, 1);
interiorRing.AddPoint(0.5, 0.5);

var invalidPolygon = new Polygon();
invalidPolygon.ExteriorRing = exteriorRing;
invalidPolygon.AddInteriorRing(interiorRing);
// invalidPolygon.IsValid == false, since polygon rings share segments (have infinite number of intersection points)

GeoJsonOptions options = new GeoJsonOptions();
options.ValidateGeometriesOnWrite = false; // false is default
File.Delete(dataDir + "not_validated_data_out.shp");
using (var nonValidatingLayer = Drivers.GeoJson.CreateLayer(dataDir + "not_validated_data_out.shp", options))
{
    Feature feature = nonValidatingLayer.ConstructFeature();
    feature.Geometry = invalidPolygon;
    // no exception is thrown, since ValidateGeometriesOnWrite == false, and GeoJson specification doesn't say that rings of polygon can't share segments.
    nonValidatingLayer.Add(feature);
}

options.ValidateGeometriesOnWrite = true;
File.Delete(dataDir + "validated_data_out.shp");
using (var validatingLayer = Drivers.GeoJson.CreateLayer(dataDir + "validated_data_out.shp", options))
{
    Feature feature = validatingLayer.ConstructFeature();
    feature.Geometry = invalidPolygon;
    try
    {
        validatingLayer.Add(feature); // GisException is thrown, since polygon is not valid
    }
    catch (GisException e)
    {
        Console.WriteLine(e.Message);
    }
}

Validierung von Geometrien beim Schreiben unter Einhaltung von Spezifikationen

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
LineString lineStrinWithOnePoint = new LineString();
lineStrinWithOnePoint.AddPoint(0, 0);

GeoJsonOptions options = new GeoJsonOptions();
options.ValidateGeometriesOnWrite = false;
using (var layer = Drivers.GeoJson.CreateLayer(dataDir + "ValidateOnWriteObeyingSpecifications_out.json", options))
{
    Feature feature = layer.ConstructFeature();
    // GeoJSON specification says that line string must have at least two coordinates.
    feature.Geometry = lineStrinWithOnePoint;

    try
    {
        // Geometry of feature doesn't match data format specification, so exception is thrown
        // regardless what ValidateGeometriesOnWrite option is.
        layer.Add(feature);
    }
    catch (GisException e)
    {
        Console.WriteLine(e.Message);
    }
}