Provides access to members that control the resolution of a spatial reference.
Members
| Name | Description | |
|---|---|---|
 |
ConstructFromHorizon | Defines the XY resolution and domain extent of this spatial reference based on the extent of its horizon. Low precision SRs will have minimum resolution of 1/10mm in current units. |
 |
MResolution | The M, or measure, resolution of this spatial reference. |
|
SetDefaultMResolution | Sets the m coordinate grid resolution to 1 mm for a low precision spatial reference or 1/10 mm for a high precision spatial reference. |
|
SetDefaultXYResolution | defaults: PCS(hi): 1/10 mm; PCS(lo): 1 mm; GCS(hi): 1/10,000 arc-second; GCS(lo): 1/500 arc-second; UCS(hi): 1/10 mm (assumed); UCS(lo): 1 mm (assumed). |
|
SetDefaultZResolution | Sets the z coordinate grid resolution to 1 mm for a low precision spatial reference or 1/10 mm for a high precision spatial reference. |
|
XYResolution | The XY resolution (distance in SR units between distinguishable grid points) of this spatial reference. Reported in meters for PCS/UCS and degrees for GCS when bStandardUnits is true or in current units of SR when it is false. |
|
ZResolution | The Z resolution (height/depth distance between distinguishable grid points) of this spatial reference. Reported in meters when bStandardUnits is true or in current units of SR when it is false. |
ISpatialReferenceResolution.ConstructFromHorizon Method
Defines the XY resolution and domain extent of this spatial reference based on the extent of its horizon. Low precision SRs will have minimum resolution of 1/10mm in current units.
Public Sub ConstructFromHorizon ( _
)
public void ConstructFromHorizon (
);
Remarks
ConstructFromHorizon defines a domain extent and resolution sufficient to cover the horizon of a given coordinate system for high precision spatial references. For low-precision spatial references the domain extent is centered on the horizon center. It does not define an extent for the Z- or M-domains; for these use methods available on ISpatialReference.
Projected Coordinate Systems
For a high precision ProjectedCoordinateSystem (PCS), ConstructFromHorizon defines the domain extent to be a square completely covering, and slightly larger than, the horizon extent of the PCS (which is an arbitrary rectangle). The scale factor (1/precision) is chosen to fit this domain.
For a low precision PCS, the center of the domain extent is aligned with the center of the horizon extent and expanded to achieve a target resolution of 1mm.
The example below lists high and low precision extents for WGS 1984 UTM Zone 11N.
| Name | Low Precision ProjectedCoordinateSystem | High Precision ProjectedCoordinateSystem |
|---|---|---|
| MinX | -573,741.824 | -5,120,900.0 |
| MinY | -1,073,741.824 | -9,998,100.0 |
| MaxX | 1,573,741.823 | 14,875,300.0 |
| MaxY | 1,073,741.823 | 9,998,100.0 |
| Resolution | 0.001 | 2.2 x 10^-9 |
Geographic Coordinate Systems
For a high precision GeographicCoordinateSystem (GCS), ConstructFromHorizon produces the square domain (-400, -400, 400, 400) (expressed in the units of the SR).
For a low precision GCS the upper right hand corner is adjusted to achieve a default resolution of 1/500 of an arc-second.
| Name | Low Precision GeographicCoordinateSystem | High Precision GeographicCoordinateSystem |
|---|---|---|
| MinX | -400 | -400 |
| MinY | -400 | -400 |
| MaxX | 793.046469444444 | 400 |
| MaxY | 793.046469444444 | 400 |
| Resolution | 5.55555555555556E-07 (1/500 arc-second) | 8.8 x 10^-14 |
Unknown Coordinate Systems
For an UnknownCoordinateSystem (UCS), the "horizon" is defined to be a square that produces a resolution of 1 millimeter for a low precision UCS or 1/10 mm for a high precision UCS.
The example below lists high and low precision extents for an UnknownCoordinateSystem.
| Name | Low Precision UnknownCoordinateSystem | High Precision UnknownCoordinateSystem |
|---|---|---|
| MinX | -1,073,741.8245 | -450,359,962,737.05 |
| MinY | -1,073,741.8245 | -450,359,962,737.05 |
| MaxX | 1,073,741.8225 | 450,359,962,737.049 |
| MaxY | 1,073,741.8225 | 450,359,962,737.049 |
| Resolution | 0.001 | 0.0001 |
ISpatialReferenceResolution.MResolution Property
The M, or measure, resolution of this spatial reference.
Public Property MResolution As Double
public double MResolution {get; set;}
Remarks
MResolution resizes the existing grid about its center to accommodate the new resolution specified. This property provides finer control for specifying the resolution than does ISpatialReferenceResolution::SetDefaultMResolution. The default MResolution is defined as 0.001 units for high and low precision spatial references.
The default value for MResolutionis NaN for a new spatial reference. If the MResolution is not well-defined (MResolution is NaN), calls to ISpatialReference::SetMDomainor ISpatialReference::SetMFalseOriginAndUnitswill set the MResolution to the minimum allowable value (2.0/mUnits). If the MResolution was already defined, these methods will not alter the MResolution.
ISpatialReferenceResolution.SetDefaultMResolution Method
Sets the m coordinate grid resolution to 1 mm for a low precision spatial reference or 1/10 mm for a high precision spatial reference.
Public Sub SetDefaultMResolution ( _
)
public void SetDefaultMResolution (
);
Remarks
This method behaves analogously to the SetDefaultXYResolution method, but operates on the linear m coordinate grid. For a high-precision spatial reference the default MResolution is 0.0001 units; for a low-precision spatial reference the default MResolution is 0.001 units.
ISpatialReferenceResolution.SetDefaultXYResolution Method
defaults: PCS(hi): 1/10 mm; PCS(lo): 1 mm; GCS(hi): 1/10,000 arc-second; GCS(lo): 1/500 arc-second; UCS(hi): 1/10 mm (assumed); UCS(lo): 1 mm (assumed).
Public Sub SetDefaultXYResolution ( _
)
public void SetDefaultXYResolution (
);
Remarks
SetDefaultXYResolution recalculates the maximum x and y coordinates for the domain of the spatial referencein order to achieve a target resolution of 1 millimeter for low precision ProjectedCoordinateSystems or 1/10 millimeter for high precision. For high precision GeographicCoordinateSystems, the target resolution is 1/10,000 of an arc-second and the low precision target resolution is 1/500 of an arc-second. For UnknownCoordinateSystems, the high precision target resolution is 1/10 millimeter and the low precision target resolution is 1 millimeter. Resolutions are listed here in metric units but are converted to the units of the spatial reference by these methods.
Use the ISpatialReferenceResolution::XYResolution(False) propertyto specify the target resolution in units defined by the spatial reference.
ISpatialReferenceResolution.SetDefaultZResolution Method
Sets the z coordinate grid resolution to 1 mm for a low precision spatial reference or 1/10 mm for a high precision spatial reference.
Public Sub SetDefaultZResolution ( _
)
public void SetDefaultZResolution (
);
Remarks
This method behaves analogously to the SetDefaultXYResolution method, but operates on the linear z coordinate grid. For a high-precision spatial reference the default ZResolution is 0.0001 meters (expressed in the units defined by the VCS if applicable); for a low-precision spatial reference the default ZResolution is 0.001 units.
ISpatialReferenceResolution.XYResolution Property
The XY resolution (distance in SR units between distinguishable grid points) of this spatial reference. Reported in meters for PCS/UCS and degrees for GCS when bStandardUnits is true or in current units of SR when it is false.
Public Function get_XYResolution ( _
ByVal bStandardUnits As Boolean _
) As Double
Public Sub set_XYResolution ( _
ByVal bStandardUnits As Boolean, _
ByVal XYResolution As Double _
)
public double get_XYResolution (
bool bStandardUnits
);
public void set_XYResolution (
bool bStandardUnits,
double XYResolution
);
Remarks
XYResolutiondetermines the distinguishable distance between two points in horizontal (XY) space. It is the inverse of the scale factor.
XYResolution can be expressed in standard units or units defined by the spatial reference. For ProjectedCoordinateSystems and UnknownCoordinateSystems the standard unit is expressed in meters; for GeographicCoordinateSystems the standard unit is expressed in degrees.
The default XYResolution for ProjectedCoordinateSystems and UnknownCoordinateSystems is either 1 mm (low-precision spatial reference) or 0.1 mm (high-precision spatial reference). For GeographicCoordinateSystems the default XYResolution is 1/500 arc-second (low-precision spatial reference) or 1/10000 arc-second (high-precision spatial reference). The precision of a spatial reference is determined using IControlPrecision2::IsHighPrecision. At ArcGIS 9.2 all spatial references are created using high precision by default.
Altering this property preserves the current false origin of the spatial reference if it has already been defined. Otherwise, the ConstructFromHorizon method is used to define a false origin.
Use ISpatialReferenceResolution::XYResolution(False) to return or set the XYResolution in the units defined as part of the spatial reference.
The default value for XYResolutionis NaN (not-a-number) for a new spatial reference. If the XYResolution has not been set previously, calls to ISpatialReference::SetDomainor ISpatialReference::SetFalseOriginAndUnitswill set the XYResolution to the minimum allowable value (2.0/XYunits).
ISpatialReferenceResolution.ZResolution Property
The Z resolution (height/depth distance between distinguishable grid points) of this spatial reference. Reported in meters when bStandardUnits is true or in current units of SR when it is false.
Public Function get_ZResolution ( _
ByVal bStandardUnits As Boolean _
) As Double
Public Sub set_ZResolution ( _
ByVal bStandardUnits As Boolean, _
ByVal ZResolution As Double _
)
public double get_ZResolution (
bool bStandardUnits
);
public void set_ZResolution (
bool bStandardUnits,
double ZResolution
);
Remarks
ZResolution resizes the existing grid about its center to achieve a target resolution of 1mm for low precision spatial references or 1/10 mm for high precision. This property provides finer control for specifying the resolution than does ISpatialReferenceResolution::SetDefaultZResolution. The default ZResolution is defined in standard units as 0.1 mm for high and low precision spatial references, or 1 mm for low precision spatial references. For ProjectedCoordinateSystems and GeographicCoordinateSystems, that default value is scaled to whatever units are associated with the spatial reference's VerticalCoordinateSystem property.
Use ISpatialReferenceResolution::ZResolution(False) to specify or retrieve the Z resolution in units defined by the vertical coordinate system.
The default value for ZResolutionis NaN for a new spatial reference. If the ZResolution is not well-defined (ZResolution is NaN), calls to ISpatialReference::SetZDomainor ISpatialReference::SetZFalseOriginAndUnitswill set the ZResolution to the minimum allowable value (2.0/zUnits). If the ZResolution was already defined, these methods will not alter the ZResolution.
Classes that implement ISpatialReferenceResolution
| Classes | Description |
|---|---|
| GeographicCoordinateSystem | Creates a geographic coordinate system. |
| ProjectedCoordinateSystem | Creates a projected coordinate system. |
| UnknownCoordinateSystem | Creates an unknown coordinate system. |
Remarks
The ISpatialReferenceResolution interface is used to define default and custom grid origins, extents and resolutions for the XY, Z and M coordinate grids associated with a spatial reference. The terms resolution and precision are synonymous within the context of the spatial reference system and the former refers to the inverse of the scale factor. Methods on this interface can define coordinate grid resolutions and extent based on a known spatial reference horizon, or alter extents and resolutions in a controlled way (for example, enlarge the extent about its current center by specifying a larger (coarser) target resolution).
//The following code shows how to use ISpatialReferenceResolution interface and methods
ISpatialReferenceFactory spatialReferenceFactory = new SpatialReferenceEnvironmentClass();
ISpatialReference spatialReference = spatialReferenceFactory.CreateESRISpatialReferenceFromPRJFile("C:\\Program Files\\ArcGIS\\Coordinate Systems\\Geographic Coordinate Systems\\World\\WGS 1984.prj");
IControlPrecision2 controlPrecision = spatialReference as IControlPrecision2;
//Flip this to false if low precision
controlPrecision.IsHighPrecision = true;
ISpatialReferenceResolution spatialReferenceResolution = spatialReference as ISpatialReferenceResolution;
//this is the KEY, Construct Horizon THEN
spatialReferenceResolution.ConstructFromHorizon();
//Set Default
spatialReferenceResolution.SetDefaultXYResolution();
double xMin;
double xMax;
double yMin;
double yMax;
spatialReference.GetDomain(out xMin, out xMax, out yMin, out yMax);
System.Windows.Forms.MessageBox.Show("Domain : " + xMin + ", " + xMax + ", " + yMin + ", " + yMax);
'The following code shows how to use ISpatialReferenceResolution interface and methods
Dim pSR As ISpatialReference2
Dim pSRF As ISpatialReferenceFactory3
Dim pSRResolution As ISpatialReferenceResolution
Dim pControlPrecision2 As IControlPrecision2
Dim XMin As Double
Dim XMax As Double
Dim YMin As Double
Dim YMax As Double
pSRF = New SpatialReferenceEnvironment
pSR = pSRF.CreateESRISpatialReferenceFromPRJFile("D:\ArcGIS\Coordinate Systems\Geographic Coordinate Systems\World\WGS 1984.prj")
pSRResolution = pSR
pControlPrecision2 = pSR
pControlPrecision2.IsHighPrecision = True 'Flip this to false if low precision
pSRResolution.ConstructFromHorizon() 'this is the KEY, Construct Horizon THEN
pSRResolution.SetDefaultXYResolution() 'Set Default
pSR.GetDomain(XMin, XMax, YMin, YMax)
Debug.Print("Domain : ", XMin, XMax, YMin, YMax)