[Tips]High and low precision spatial references

지오데이터베이스(GeoDatabase - personal geodatabase, file geodatabase, ArcSDE)에서 9.2 버전부터 high-precision spatial reference를 default로 사용한다.

9.2 이전 버전의 low-precision spatial reference를 사용하는 지오데이터베이스 피쳐클래스의 spatial reference 정보를 이용하여 high-precision 지오데이터베이스에 FeaureClass를 생성하는 경우에 다음과 같은 오류가 발생하는 경우가 있다.

<Cannot create a low precision dataset in a high precision database>

또는

<The XY domain on the spatial reference is not set or invalid>

다음은 이 오류를 해결하는 방법을 설명하며, 전체 코드는 마지막 ④ 해결을 위한 전체 코드를 참고하면 된다.

① 현재 접속한 Workspace가 High-Precision Workspace인지를 판별하는 방법
다음 코드는 현재 접속한 Workspace가 high-precision을 사용하는 workspace인지를 판별하는 코드이다.
[code c#]
private bool IsHighPrecisionWorkspace(IWorkspace Workspace)
{
    bool isHighPrecision = false;

    if (Workspace is IWorkspaceProperties)
    {
        IWorkspaceProperties ipWsProps = (IWorkspaceProperties)Workspace;

        IWorkspaceProperty ipProp = ipWsProps.get_Property(
            esriWorkspacePropertyGroupType.esriWorkspacePropertyGroup,
            (int)esriWorkspacePropertyType.esriWorkspacePropSupportsHighPrecisionStorage);

        if (ipProp.IsSupported)
        {
            isHighPrecision = Convert.ToBoolean(ipProp.PropertyValue);
        }
    }
    return isHighPrecision;
}
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② How to construct a high- or low-precision spatial reference
출처 : http://resources.esri.com/help/9.3/ArcGISEngine/dotnet/0682A7EC-2C4D-4e93-B664-957A1AE7185A.htm

다음 코드는 high-precision spatial reference와 low-precision spatial reference를 생성하며, 각 precision에 맞는 default resolution and default tolerance를 설정하는 코드이다.

펼쳐두기..

[code c#]
private void ConstructCoordinateSystem(bool highPrecision)
{
  ISpatialReferenceFactory3 spatialReferenceFactory = new
    SpatialReferenceEnvironmentClass();
  ISpatialReference3 spatialReference =
    spatialReferenceFactory.CreateESRISpatialReferenceFromPRJFile(
    "C:\\Program Files\\ArcGIS\\Coordinate Systems\\Geographic Coordinate Systems\\World\\WGS 1984.prj")as ISpatialReference3;

  IControlPrecision2 controlPrecision = spatialReference as IControlPrecision2;

  //Determines whether you are constructing a high- or low-precision spatial reference.
  controlPrecision.IsHighPrecision = highPrecision;
  ISpatialReferenceResolution spatialReferenceResolution = spatialReference as
    ISpatialReferenceResolution;

  //These three methods are the keys; construct horizon, then set the default x,y resolution and tolerance.
  spatialReferenceResolution.ConstructFromHorizon();

  //Set the default x,y resolution value.
  spatialReferenceResolution.SetDefaultXYResolution();

  //Set the default x,y tolerance value.
  ISpatialReferenceTolerance spatialReferenceTolerance = spatialReference as
    ISpatialReferenceTolerance;
  spatialReferenceTolerance.SetDefaultXYTolerance();

  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);
}
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③ How to convert between high and low precision spatial references
출처 : http://resources.esri.com/help/9.3/ArcGISEngine/dotnet/A98B72CF-A833-4dc8-A4D3-48F5044210FF.htm

이 문서 및 샘플 코드는 low-precision spatial reference (pre-9.2)를 high-precision spatial reference로 변환하는 예이다.

펼쳐두기..

[code c#]
private void LowHighConversion_Example(IFeatureClass pre92FeatureClass)
{
  IGeoDataset pre92GeoDataset = pre92FeatureClass as IGeoDataset;

  ISpatialReference pre92SpatialReference = pre92GeoDataset.SpatialReference;

  double falseX;
  double falseY;
  double xyUnits;
  pre92SpatialReference.GetFalseOriginAndUnits(out falseX, out falseY, out
    xyUnits);

  System.Windows.Forms.MessageBox.Show(
    "Low precision coordinate grid definition:\n" + "false x: " + falseX +
    ", false y: " + falseY + ", scale factor: " + xyUnits);


  ISpatialReferenceFactory3 spatialReferenceFactory = new
    SpatialReferenceEnvironmentClass();
  ISpatialReference spatialReference92 =
    spatialReferenceFactory.ConstructHighPrecisionSpatialReference
    (pre92SpatialReference,  - 1,  - 1,  - 1);

  spatialReference92.GetFalseOriginAndUnits(out falseX, out falseY, out xyUnits)
    ;
  System.Windows.Forms.MessageBox.Show(
    "high precision coordinate grid definition:\n" + "false x: " + falseX +
    ", false y: " + falseY + ", scale factor: " + xyUnits);
}
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④ 오류 해결을 위한 전체 코드
다음 코드는 low-precision spatial reference를 사용하는 FeatureClass와 동일한 필드 및 spatial reference를 사용하는 FeatureClass를 high-precision Workspace에 생성하는 코드이다.

IsHighPrecision, ConstructFromHorizon, SetDefaultXYResolution, SetDefaultXYTolerance가 이 코드의 핵심이다.

펼쳐두기..

[code c#]
private void CreateFeatureClass_Sample()
{  
    IWorkspace pre92Workspace, highPrecisionWs;
    IFeatureClass pre92Fc, highPrecisionFc;
             
    pre92Workspace = OpenPre92AccessWorkspace();
    pre92Fc = OpenPre92FeatureClass(pre92Workspace, "클래스명");  
    highPrecisionWs = OpenHighPrecisionWorkspace();
  
    IFeatureWorkspace highPrecisionFWs = (IFeatureWorkspace)highPrecisionWs;
  
    //0. clone fields
    IFields newFields = (IFields)((IClone)pre92Fc.Fields).Clone();
  
    //1. low-precision spatialreference를 그대로 사용하면 오류 발생
    //highPrecisionFc = highPrecisionFWs.CreateFeatureClass("HIGH_PRE_FC", newFields, null, null, esriFeatureType.esriFTSimple, pre92Fc.ShapeFieldName, string.Empty);
  
    //2. High-precision으로 전환 후 필드에 적용
    //check high-precision workspace
    bool isHighPrecisionWorkspace = this.IsHighPrecisionWorkspace(highPrecisionWs);
  
    //get geometry field
    IField geometryField = null;
    for (int k = 0; k < newFields.FieldCount; k++)
    {
        if (newFields.get_Field(k).Type == esriFieldType.esriFieldTypeGeometry)
        {
            geometryField = newFields.get_Field(k);
            break;
        }
    }
  
    //modify spatialreference
    IGeometryDefEdit geomDefEdit = (IGeometryDefEdit)geometryField.GeometryDef;
    ISpatialReference pre92Sr = geomDefEdit.SpatialReference;         
  
    IControlPrecision2 controlPrecision = (IControlPrecision2)pre92Sr;
    if (isHighPrecisionWorkspace && !controlPrecision.IsHighPrecision)
    {
        controlPrecision.IsHighPrecision = isHighPrecisionWorkspace;
    }
  
    //construct horizon, then set the default x,y resolution and tolerance.
    ISpatialReferenceResolution srResolution = (ISpatialReferenceResolution)pre92Sr;
    ISpatialReferenceTolerance srTolerance = (ISpatialReferenceTolerance)pre92Sr;
  
    srResolution.ConstructFromHorizon();
    srResolution.SetDefaultXYResolution();
    srTolerance.SetDefaultXYTolerance();
  
    //check z, m
    if (geomDefEdit.HasZ || geomDefEdit.HasM)
    {
        srResolution.SetDefaultZResolution();
        srResolution.SetDefaultMResolution();
  
        srTolerance.SetDefaultZTolerance();
        srTolerance.SetMinimumMTolerance();
    }
  
    //3. create featureclass
    highPrecisionFc = highPrecisionFWs.CreateFeatureClass("HIGH_PRE_FC", newFields, null, null, esriFeatureType.esriFTSimple, pre92Fc.ShapeFieldName, string.Empty);
  
    System.Diagnostics.Debug.WriteLine("OK");
}

private bool IsHighPrecisionWorkspace(IWorkspace Workspace)
{
    bool isHighPrecision = false;

    if (Workspace is IWorkspaceProperties)
    {
        IWorkspaceProperties ipWsProps = (IWorkspaceProperties)Workspace;

        IWorkspaceProperty ipProp = ipWsProps.get_Property(
            esriWorkspacePropertyGroupType.esriWorkspacePropertyGroup,
            (int)esriWorkspacePropertyType.esriWorkspacePropSupportsHighPrecisionStorage);

        if (ipProp.IsSupported)
        {
            isHighPrecision = Convert.ToBoolean(ipProp.PropertyValue);
        }
    }
    return isHighPrecision;
}
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