Geometry (arcpy)

Récapitulatif

Geometry objects define a spatial location and an associated geometric shape.

Discussion

Dans de nombreux workflows de géotraitement, vous devez éventuellement exécuter une opération spécifique à l'aide d'informations sur les coordonnées et la géométrie, sans vouloir nécessairement créer une nouvelle classe d'entités (temporaire), la remplir avec des curseurs, l'utiliser, puis la supprimer. Les objets géométrie peuvent alors être utilisés en entrée et en sortie afin de simplifier le géotraitement. Les objets géométrie peuvent être entièrement créés à l'aide des classes Geometry, Multipoint, PointGeometry, Polygon ou Polyline.

Syntaxe

Geometry (geometry, inputs, {spatial_reference}, {has_z}, {has_m})

Paramètre	Explication	Type de données
geometry	The geometry type: point, polygon, polyline, or multipoint.	String
inputs	The coordinates used to create the object. The datatype can be either Point or Array objects.	Object
spatial_reference	The spatial reference of the new geometry. (La valeur par défaut est None)	SpatialReference
has_z	The Z state: True for geometry if Z is enabled and False if it is not. (La valeur par défaut est False)	Boolean
has_m	The M state: True for geometry if M is enabled and False if it is not. (La valeur par défaut est False)	Boolean

Propriétés

Propriété	Explication	Type de données
JSON (Lecture seule)	Returns a JSON representation of the geometry as a string. Astuce: The returned string can be converted to a dictionary by Python's eval function.	String
WKB (Lecture seule)	Returns the well-known binary (WKB) representation for OGC geometry. It provides a portable representation of a geometry value as a contiguous stream of bytes.	Bytearray
WKT (Lecture seule)	Returns the well-known text (WKT) representation for OGC geometry. It provides a portable representation of a geometry value as a text string.	String
area (Lecture seule)	The area of a polygon feature. Empty for all other feature types.	Double
centroid (Lecture seule)	The true centroid if it is within or on the feature; otherwise, the label point is returned. Returns a point object.	Point
extent (Lecture seule)	The extent of the geometry.	Extent
firstPoint (Lecture seule)	The first coordinate point of the geometry.	Point
hullRectangle (Lecture seule)	A space-delimited string of the coordinate pairs of the convex hull rectangle.	String
isMultipart (Lecture seule)	True, if the number of parts for this geometry is more than one.	Boolean
labelPoint (Lecture seule)	The point at which the label is located. The labelPoint is always located within or on a feature.	Point
lastPoint (Lecture seule)	The last coordinate of the feature.	Point
length (Lecture seule)	The length of the linear feature. Zero for point and multipoint feature types.	Double
length3D (Lecture/écriture)	The 3D length of the linear feature. Zero for point and multipoint feature types.	Double
partCount (Lecture seule)	The number of geometry parts for the feature.	Integer
pointCount (Lecture seule)	The total number of points for the feature.	Integer
trueCentroid (Lecture seule)	The center of gravity for a feature.	Point
type (Lecture seule)	The geometry type: polygon, polyline, point, multipoint, multipatch, dimension, or annotation.	String

Vue d'ensemble des méthodes

Méthode	Explication
boundary ()	Constructs the boundary of the geometry.
buffer (distance)	Constructs a polygon at a specified distance from the geometry.
clip (envelope)	Constructs the intersection of the geometry and the specified extent.
contains (second_geometry)	Indique si la géométrie de base contient la géométrie de comparaison. contains est le contraire de within. Only True relationships are shown in this illustration.
convexHull ()	Constructs the geometry that is the minimal bounding polygon such that all outer angles are convex.
crosses (second_geometry)	Indique si les deux géométries s'intersectent dans une géométrie de type de forme inférieure. Deux polylignes se croisent si elles partagent uniquement des points, dont au moins un n'est pas une extrémité. Une polyligne et un polygone se croisent s'ils partagent une polyligne ou un point (pour une ligne verticale) à l'intérieur du polygone qui n'est pas équivalent à la polyligne entière. Only True relationships are shown in this illustration.
difference (other)	Constructs the geometry that is composed only of the region unique to the base geometry but not part of the other geometry. The following illustration shows the results when the red polygon is the source geometry.
disjoint (second_geometry)	Indique si la géométrie de base et la géométrie de comparaison n'ont aucun point en commun. Deux géométries s'intersectent si la propriété disjoint renvoie False. Only True relationships are shown in this illustration.
distanceTo (other)	Returns the minimum distance between two geometries. If the geometries intersect, the minimum distance is 0. Both geometries must have the same projection.
equals (second_geometry)	Indicates if the base and comparison geometries are of the same shape type and define the same set of points in the plane. This is a 2D comparison only; M and Z values are ignored. Only True relationships are shown in this illustration.
getArea (type)	Returns the area of the feature using a measurement type.
getLength (measurement_type)	Returns the length of the feature using a measurement type.
getPart ({index})	Returns an array of point objects for a particular part of geometry or an array containing a number of arrays, one for each part.
intersect (other, dimension)	Constructs a geometry that is the geometric intersection of the two input geometries. Different dimension values can be used to create different shape types. The intersection of two geometries of the same shape type is a geometry containing only the regions of overlap between the original geometries. For faster results, test if the two geometries are disjoint before calling intersect.
overlaps (second_geometry)	Indique si l'intersection des deux géométries possède le même type de forme que l'une des géométries en entrée et qu'elle n'est pas équivalente à l'une des géométries en entrée. Only True relationships are shown in this illustration.
positionAlongLine (value, {use_percentage})	Returns a point on a line at a specified distance from the beginning of the line.
projectAs (spatial_reference, {transformation_name})	Projects a geometry and optionally applies a geotransformation. To project, the geometry needs to have a spatial reference, and not have an UnknownCoordinateSystem. The new spatial reference system passed to the method defines the output coordinate system. If either spatial reference is unknown the coordinates will not be changed. The Z- and measure values are not changed by the ProjectAs method.
symmetricDifference (other)	Constructs the geometry that is the union of two geometries minus the instersection of those geometries. The two input geometries must be the same shape type.
touches (second_geometry)	Indique si les limites des géométries s'intersectent. Deux géométries se touchent lorsque l'intersection des géométries n'est pas vide, mais que l'intersection de leurs intérieurs est vide. Par exemple, un point touche une polyligne uniquement s'il coïncide avec l'une des extrémités de la polyligne. Only True relationships are shown in this illustration.
union (other)	Constructs the geometry that is the set-theoretic union of the input geometries. The two geometries being unioned must be the same shape type.
within (second_geometry)	Indique si la géométrie de base se trouve dans la géométrie de comparaison. within est l'opérateur contraire de contains. Only True relationships are shown in this illustration.

Méthodes

boundary ()

Valeur renvoyée

Type de données	Explication
Object	A polygon's boundary is a polyline. A polyline's boundary is a multipoint, corresponding to the endpoints of the line. A point or multipoint's boundary is an empty point or multipoint.

buffer (distance)

Paramètre	Explication	Type de données
distance	The buffer distance. The buffer distance is in the same units as the geometry that is being buffered. A negative distance can only be specified against a polygon geometry.	Double

Valeur renvoyée

Type de données	Explication
Polygon	The buffered polygon geometry.

clip (envelope)

Paramètre	Explication	Type de données
envelope	An extent object used to define the clip extent.	Extent

Valeur renvoyée

Type de données	Explication
Object	An output geometry clipped to the specified extent.

contains (second_geometry)

Paramètre	Explication	Type de données
second_geometry	A second geometry.	Object

Valeur renvoyée

Type de données	Explication
Boolean	Une valeur booléenne renvoyée True indique que cette géométrie contient la deuxième géométrie.

convexHull ()

Valeur renvoyée

Type de données	Explication
Object	The resulting geometry. The convex hull of a single point is the point itself.

crosses (second_geometry)

Paramètre	Explication	Type de données
second_geometry	A second geometry.	Object

Valeur renvoyée

Type de données	Explication
Boolean	Une valeur booléenne renvoyée True indique que les deux géométries s'intersectent dans une géométrie de type de forme inférieure.

difference (other)

Paramètre	Explication	Type de données
other	A second geometry.	Object

Valeur renvoyée

Type de données	Explication
Object	The resulting geometry.

disjoint (second_geometry)

Paramètre	Explication	Type de données
second_geometry	A second geometry.	Object

Valeur renvoyée

Type de données	Explication
Boolean	Une valeur booléenne renvoyée True indique que les deux géométries n'ont aucun point en commun.

distanceTo (other)

Paramètre	Explication	Type de données
other	A second geometry.	Object

Valeur renvoyée

Type de données	Explication
Double	The distance between the two geometries.

equals (second_geometry)

Paramètre	Explication	Type de données
second_geometry	A second geometry.	Object

Valeur renvoyée

Type de données	Explication
Boolean	A return Boolean value of True indicates that the two geometries are of the same shape type and define the same set of points in the plane.

getArea (type)

Paramètre	Explication	Type de données
type	PLANAR measurements reflect the projection of geographic data onto the 2D surface (in other words, they will not take into account the curvature of the earth). GEODESIC, GREAT_ELLIPTIC, LOXODROME, and PRESERVE_SHAPE measurement types may be chosen as an alternative, if desired. GEODESIC —The shortest line between any two points on the earth's surface on a spheroid (ellipsoid). One use for a geodesic line is when you want to determine the shortest distance between two cities for an airplane's flight path. This is also known as a great circle line if based on a sphere rather than an ellipsoid. GREAT_ELLIPTIC —The line on a spheroid (ellipsoid) defined by the intersection at the surface by a plane that passes through the center of the spheroid and the start and endpoints of a segment. This is also known as a great circle when a sphere is used. LOXODROME —A loxodrome is not the shortest distance between two points but instead defines the line of constant bearing, or azimuth. Great circle routes are often broken into a series of loxodromes, which simplifies navigation. This is also known as a rhumb line. PLANAR —Planar measurement use 2D Cartesian mathematics to calculate lengths and areas. This option is only available when measuring in a projected coordinate system and the 2D plane of that coordinate system will be used as the basis for the measurements. PRESERVE_SHAPE —This type calculates the area or length of the geometry on the surface of the Earth ellipsoid, for geometry defined in a projected or geographic coordinate system. This option preserves the shape of the geometry in its coordinate system.	String

Valeur renvoyée

Type de données	Explication
Double	The area of the feature. Areas are always returned in square meters.

getLength (measurement_type)

Paramètre	Explication	Type de données
measurement_type	PLANAR measurements reflect the projection of geographic data onto the 2D surface (in other words, they will not take into account the curvature of the earth). GEODESIC, GREAT_ELLIPTIC, LOXODROME, and PRESERVE_SHAPE measurement types may be chosen as an alternative, if desired. GEODESIC —The shortest line between any two points on the earth's surface on a spheroid (ellipsoid). One use for a geodesic line is when you want to determine the shortest distance between two cities for an airplane's flight path. This is also known as a great circle line if based on a sphere rather than an ellipsoid. GREAT_ELLIPTIC —The line on a spheroid (ellipsoid) defined by the intersection at the surface by a plane that passes through the center of the spheroid and the start and endpoints of a segment. This is also known as a great circle when a sphere is used. LOXODROME —A loxodrome is not the shortest distance between two points but instead defines the line of constant bearing, or azimuth. Great circle routes are often broken into a series of loxodromes, which simplifies navigation. This is also known as a rhumb line. PLANAR —Planar measurement use 2D Cartesian mathematics to calculate lengths and areas. This option is only available when measuring in a projected coordinate system and the 2D plane of that coordinate system will be used as the basis for the measurements. PRESERVE_SHAPE —This type calculates the area or length of the geometry on the surface of the Earth ellipsoid, for geometry defined in a projected or geographic coordinate system. This option preserves the shape of the geometry in its coordinate system.	String

Valeur renvoyée

Type de données	Explication
Double	The length of the linear feature. Lengths are always returned in meters.

getPart ({index})

Paramètre	Explication	Type de données
index	The index position of the geometry.	Integer

Valeur renvoyée

Type de données	Explication
Array	getPart returns an array of point objects for a particular part of the geometry if an index is specified. If an index is not specified, an array containing an array of point objects for each geometry part is returned.

intersect (other, dimension)

Paramètre	Explication	Type de données
other	The second geometry.	Object
dimension	The topological dimension (shape type) of the resulting geometry. 1 —A zero-dimensional geometry (point or multipoint). 2 —A one-dimensional geometry (polyline). 4 —A two-dimensional geometry (polygon).	Integer

Valeur renvoyée

Type de données	Explication
Object	A new geometry (point, multipoint, polyline, or polygon) that is the geometric intersection of the two input geometries.

overlaps (second_geometry)

Paramètre	Explication	Type de données
second_geometry	A second geometry.	Object

Valeur renvoyée

Type de données	Explication
Boolean	Une valeur booléenne renvoyée True indique que l'intersection des deux géométries a la même dimension que l'une des géométries en entrée.

positionAlongLine (value, {use_percentage})

Paramètre	Explication	Type de données
value	The distance along the line. If the distance is less than zero, then the starting point of the line will be returned; if the distance is greater than the length of the line, then the end point of the line will be returned.	Double
use_percentage	The distance may be specified as a fixed unit of measure or a ratio of the length of the line. If True, value is used as a percentage; if False, value is used as a distance. (La valeur par défaut est False)	Boolean

Valeur renvoyée

Type de données	Explication
PointGeometry	The point on the line at a specified distance from the beginning of the line.

projectAs (spatial_reference, {transformation_name})

Paramètre	Explication	Type de données
spatial_reference	The new spatial reference. This can be a SpatialReference object or the coordinate system name.	SpatialReference
transformation_name	The geotransformation name.	String

Valeur renvoyée

Type de données	Explication
Object	The projected geometry.

symmetricDifference (other)

Paramètre	Explication	Type de données
other	A second geometry.	Object

Valeur renvoyée

Type de données	Explication
Object	The resulting geometry.

touches (second_geometry)

Paramètre	Explication	Type de données
second_geometry	A second geometry.	Object

Valeur renvoyée

Type de données	Explication
Boolean	Une valeur booléenne renvoyée True indique que les limites des géométries s'intersectent.

union (other)

Paramètre	Explication	Type de données
other	A second geometry.	Object

Valeur renvoyée

Type de données	Explication
Object	The resulting geometry.

within (second_geometry)

Paramètre	Explication	Type de données
second_geometry	A second geometry.	Object

Valeur renvoyée

Type de données	Explication
Boolean	Une valeur booléenne renvoyée True indique que cette géométrie est contenue dans la deuxième géométrie.

Exemple de code

Geometry example

When you set the output parameter of a geoprocessing tool to a empty Geometry object, the tool will return a list of Geometry objects.

import arcpy

# Create an empty Geometry object
#
g = arcpy.Geometry()

# Run the CopyFeatures tool, setting the output to the geometry object.  GeometryList
#  is returned as a list of geometry objects.
#  
geometryList = arcpy.CopyFeatures_management("c:/data/streets.shp", g)

# Walk through each geometry, totalling the length
#
length = 0
for geometry in geometryList:
    length += geometry.length

print "Total length: %f" % length