Question

我想将geom（几何）数据类型转换为GEOJSON。我怎么能这样做？

例如，WKT中的几何图形：

    POLYGON((455216.346127297 4288433.28426224,455203.386722146 4288427.76317716,455207.791765017 4288417.51116228,455220.784166744 4288423.30230044,455216.346127297 4288433.28426224))

以下GeoJSON：

{ "type": "Polygon",
    "coordinates": [
      [ [100.0, 0.0], [101.0, 0.0], [101.0, 1.0], [100.0, 1.0], [100.0, 0.0] ],
      [ [100.2, 0.2], [100.8, 0.2], [100.8, 0.8], [100.2, 0.8], [100.2, 0.2] ]
      ]
   }

Answer 1

我认为，当您从Sql Server获取数据时，可以在服务器端生成geojson。

您应该检查GeoJSON.Net和similar question

var modelF = new List<GeoJSON.Net.Feature.Feature>();
foreach (DataRow dr in ds.Tables[0].Rows)
     {
       var point = new GeoJSON.Net.Geometry.Point(new GeoJSON.Net.Geometry.GeographicPosition(Convert.ToDouble(dr["latitude"].ToString()), Convert.ToDouble(dr["longitude"].ToString())));
       var featureProperties = new Dictionary<string, object> { };
       foreach (DataColumn dataColumn in ds.Tables[0].Columns)
            {
              featureProperties.Add(dataColumn.ColumnName, dr[dataColumn].ToString());
            }
       modelF.Add(new GeoJSON.Net.Feature.Feature(point, featureProperties));
     }
var fcol = new FeatureCollection(modelF);
var serializedData = JsonConvert.SerializeObject(fcol, Formatting.Indented, new JsonSerializerSettings { ContractResolver = new CamelCasePropertyNamesContractResolver(), NullValueHandling = NullValueHandling.Ignore });
return serializedData;

有个疯狂的日子。

Answer 2

我有同样的需要。我们有一个包含SQL Server中GEOMETRY列的表的大型数据库。我觉得能够从包含GeoJson的存储过程获得单个字符串对象更为可取。我编写了一个函数，它将一个几何实例作为一个对象，并返回一个GeoJson字符串。

CREATE FUNCTION [dbo].[geomToGeoJSON] (@geom GEOMETRY)
RETURNS VARCHAR(MAX)
AS
BEGIN
-- Declare the return variable here
    DECLARE @geoJSON VARCHAR(MAX)


    DECLARE @Ngeom GEOMETRY
    DECLARE @ptCounter INT
    DECLARE @numPt INT
    DECLARE @ringCounter INT
    DECLARE @numRing INT
    DECLARE @gCounter INT
    DECLARE @numGeom INT
    DECLARE @handled BIT = 0
    DECLARE @extRing GEOMETRY
    DECLARE @intRing GEOMETRY

    -- fix bad geometries and enforce ring orientation
    SET @geom = @geom.STUnion(@geom.STPointN(1)).MakeValid()

    -- Point ----------------------------
    IF (@geom.STGeometryType() = 'Point')
    BEGIN
        SET @geoJSON = '{ "type": "Point", "coordinates": [' + LTRIM(RTRIM(STR(@geom.STX, 38, 8))) + ', ' + LTRIM(RTRIM(STR(@geom.STY, 38, 8))) + '] }'
        SET @handled = 1
    END


    -- MultiPoint ---------------------------------------------
    IF (
        @handled = 0
        AND @geom.STGeometryType() = 'MultiPoint'
        )
    BEGIN
        SET @gCounter = 1
        SET @numGeom = @geom.STNumGeometries()

        SET @geoJSON = '{ "type": "MultiPoint", "coordinates": ['

        WHILE @gCounter <= @numGeom
        BEGIN
            SET @geoJSON += '[' + LTRIM(RTRIM(STR(@geom.STGeometryN(@gCounter).STX, 38, 8))) + ', ' + LTRIM(RTRIM(STR(@geom.STGeometryN(@gCounter).STY, 38, 8))) + '], '
            SET @gCounter += 1
        END

        SET @geoJSON = LEFT(@geoJSON, LEN(@geoJSON) - 1) + '] }'
        SET @handled = 1
    END




    -- LineString ---------------------------------------------
    IF (
        @handled = 0
        AND @geom.STGeometryType() = 'LineString'
        )
    BEGIN
        SET @ptCounter = 1
        SET @numPt = @geom.STNumPoints()

        SET @geoJSON = '{ "type": "LineString", "coordinates": ['

        WHILE @ptCounter <= @numPt
        BEGIN
            SET @geoJSON += '[' + LTRIM(RTRIM(STR(@geom.STPointN(@ptCounter).STX, 38, 8))) + ', ' + LTRIM(RTRIM(STR(@geom.STPointN(@ptCounter).STY, 38, 8))) + '], '
            SET @ptCounter += 1
        END

        SET @geoJSON = LEFT(@geoJSON, LEN(@geoJSON) - 1) + ' ] }'
        SET @handled = 1
    END




    -- MultiLineString ---------------------------------------------
    IF (
        @handled = 0
        AND @geom.STGeometryType() = 'MultiLineString'
        )
    BEGIN
        SET @gCounter = 1
        SET @numGeom = @geom.STNumGeometries()

        SET @geoJSON = '{ "type": "MultiLineString", "coordinates": ['

        WHILE @gCounter <= @numGeom
        BEGIN
            SET @Ngeom = @geom.STGeometryN(@gCounter)
            SET @geoJSON += '['
            SELECT
                @ptCounter = 1
                ,@numPt = @Ngeom.STNumPoints()

            WHILE @ptCounter <= @numPt
            BEGIN
                SET @geoJSON += '[' + LTRIM(RTRIM(STR(@Ngeom.STPointN(@ptCounter).STX, 38, 8))) + ', ' + LTRIM(RTRIM(STR(@Ngeom.STPointN(@ptCounter).STY, 38, 8))) + '], '
                SET @ptCounter += 1
            END

            SET @geoJSON = LEFT(@geoJSON, LEN(@geoJSON) - 1) + '],'

            SET @gCounter += 1
        END

        SET @geoJSON = LEFT(@geoJSON, LEN(@geoJSON) - 1) + '] }'
        SET @handled = 1
    END




    -- Polygon ---------------------------------------------
    IF (
        @handled = 0
        AND @geom.STGeometryType() = 'Polygon'
        )
    BEGIN
        SET @extRing = @geom.STExteriorRing()

        SET @geoJSON = '{ "type": "Polygon", "coordinates": [['

        SELECT
            @ptCounter = 1
            ,@numPt = @extRing.STNumPoints()

        WHILE @ptCounter <= @numPt
        BEGIN
            SET @geoJSON += '[' + LTRIM(RTRIM(STR(@extRing.STPointN(@ptCounter).STX, 38, 8))) + ', ' + LTRIM(RTRIM(STR(@extRing.STPointN(@ptCounter).STY, 38, 8))) + '], '
            SET @ptCounter += 1
        END

        SET @geoJSON = LEFT(@geoJSON, LEN(@geoJSON) - 1) + ']'

        SET @ringCounter = 1
        SET @numRing = @geom.STNumInteriorRing()

        WHILE @ringCounter <= @numRing
        BEGIN
            SET @geoJSON += ',['

            SET @intRing = @geom.STInteriorRingN(@ringCounter)
            -- set the ring orientation so that they are consistent
            SET @intRing = @intRing.STUnion(@intRing.STPointN(1)).MakeValid()

            SELECT
                @ptCounter = @intRing.STNumPoints()

            WHILE @ptCounter > 0
            BEGIN
                SET @geoJSON += '[' + LTRIM(RTRIM(STR(@intRing.STPointN(@ptCounter).STX, 38, 8))) + ', ' + LTRIM(RTRIM(STR(@intRing.STPointN(@ptCounter).STY, 38, 8))) + '], '
                SET @ptCounter -= 1
            END

            SET @geoJSON = LEFT(@geoJSON, LEN(@geoJSON) - 1) + ']'

            SET @ringCounter += 1
        END

        SET @geoJSON = LEFT(@geoJSON, LEN(@geoJSON) - 1) + ']] }'
        SET @handled = 1
    END




    -- MultiPolygon ---------------------------------------------
    IF (
        @handled = 0
        AND @geom.STGeometryType() = 'MultiPolygon'
        )
    BEGIN
        SELECT
            @gCounter = 1
            ,@numGeom = @geom.STNumGeometries()

        SET @geoJSON = '{ "type": "MultiPolygon", "coordinates": ['

        WHILE @gCounter <= @numGeom
        BEGIN
            SET @Ngeom = @geom.STGeometryN(@gCounter)

            SET @extRing = @Ngeom.STExteriorRing()

            SET @geoJSON += '[['

            SELECT
                @ptCounter = 1
                ,@numPt = @extRing.STNumPoints()

            -- add the exterior ring points to the json
            WHILE @ptCounter <= @numPt
            BEGIN
                SET @geoJSON += '[' + LTRIM(RTRIM(STR(@extRing.STPointN(@ptCounter).STX, 38, 8))) + ', ' + LTRIM(RTRIM(STR(@extRing.STPointN(@ptCounter).STY, 38, 8))) + '], '
                SET @ptCounter += 1
            END

            SET @geoJSON = LEFT(@geoJSON, LEN(@geoJSON) - 1) + ']'

            SET @ringCounter = 1
            SET @numRing = @Ngeom.STNumInteriorRing()

            -- add any internal ring points to the json
            WHILE @ringCounter <= @numRing
            BEGIN
                SET @geoJSON += ',['

                SET @intRing = @Ngeom.STInteriorRingN(@ringCounter)
                -- make sure the ring orientation is the same every time
                SET @intRing = @intRing.STUnion(@intRing.STPointN(1)).MakeValid()

                SELECT
                    @ptCounter = @intRing.STNumPoints()

                WHILE @ptCounter > 0
                BEGIN
                    SET @geoJSON += '[' + LTRIM(RTRIM(STR(@intRing.STPointN(@ptCounter).STX, 38, 8))) + ', ' + LTRIM(RTRIM(STR(@intRing.STPointN(@ptCounter).STY, 38, 8))) + '], '
                    SET @ptCounter -= 1
                END

                SET @geoJSON = LEFT(@geoJSON, LEN(@geoJSON) - 1) + ']'

                SET @ringCounter += 1
            END



            SET @geoJSON += '],'
            SET @gCounter += 1
        END

        SET @geoJSON = LEFT(@geoJSON, LEN(@geoJSON) - 1) + '] }'
        SET @handled = 1
    END






    IF (@handled = 0)
    BEGIN
        SET @geoJSON = '{"type": "' + @geom.STGeometryType() + '", "coordinates": []}'
    END




    RETURN @geoJSON



END

然后我可以像这样选择一个单独的GeoJSON对象：

    SELECT dbo.geomToGeoJSON(GEOMCOLNAME) FROM DB.gis.PARCEL WHERE PARCEL = 'R1525750900'

并获得类似

的结果

    {
        "type": "Polygon",
        "coordinates": [
            [
                [-116.27593761, 43.62939598],
                [-116.27558219, 43.62939633],
                [-116.27558253, 43.62955520],
                [-116.27582493, 43.62955445],
                [-116.27582534, 43.62963010],
                [-116.27593893, 43.62962975],
                [-116.27593761, 43.62939598]
            ]
        ]
    }

或者我可以将整组对象打包成FeatureCollection，如下所示：

        DECLARE @GeoJSON VARCHAR(MAX)
        SET @GeoJSON = '{"type": "FeatureCollection", "features": ['

        SELECT
            @GeoJSON += '{"type": "Feature", "geometry": ' + sde_apps.dbo.geomToGeoJSON(SHAPE) + ', "properties": { "Parcel": "' + PARCEL + '"}},'
        FROM
            db.gis.PARCEL
        WHERE
            SUBNM LIKE @subnm


        SET @GeoJSON = LEFT(@GeoJSON, LEN(@GeoJSON) - 1) + ']}'

        SELECT
            @GeoJSON

查询性能取决于几何的复杂程度和数量，但我通常会得到~2分之几秒的结果。

我已使用MSDN中的示例几何进行验证，然后将生成的GeoJSON输入http://geojsonlint.com/。我知道这已经有一年了，但我仍然有需要，我怀疑没有地图服务器的人可以使用类似的东西生成他们自己的简单地图服务器，以便在Bing地图上绘制图层等。

Answer 3

如果您有权访问PostgreSQL / PostGIS，可以使用ST_GeomFromText读取几何图形，ST_AsGeoJSON将几何图形保存为GeoJSON：

SELECT ST_AsGeoJSON(ST_GeomFromText('POLYGON((455216.346127297 
 4288433.28426224,455203.386722146 4288427.76317716,455207.791765017
 4288417.51116228,455220.784166744 4288423.30230044,455216.346127297
 4288433.28426224))'));

，生成：

-------------------------------------------------------------------------------

 {"type":"Polygon","coordinates":[[[455216.346127297,4288433.28426224],
[455203.386722146,4288427.76317716],[455207.791765017,4288417.51116228],
[455220.784166744,4288423.30230044],[455216.346127297,4288433.28426224]]]}

    (1 row)

Answer 4

这对我有用（SQL Server）

  CREATE FUNCTION dbo.GEO_to_json( @geo GEOGRAPHY)
RETURNS nvarchar(MAX) AS
BEGIN
RETURN  
(SELECT
'{' +
(CASE @geo.STGeometryType()
WHEN 'POINT' THEN
'"type": "Point","coordinates":' +
REPLACE(REPLACE(REPLACE(REPLACE(@geo.ToString(),'POINT ',''),'(','['),')',']'),' ',',')
WHEN 'POLYGON' THEN
'"type": "Polygon","coordinates":' +
'[' + REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(@geo.ToString(),'POLYGON ',''),'(','['),')',']'),'], ',']],['),', ','],['),' ',',') + ']'
WHEN 'MULTIPOLYGON' THEN
'"type": "MultiPolygon","coordinates":' +
'[' + REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(@geo.ToString(),'MULTIPOLYGON ',''),'(','['),')',']'),'], ',']],['),', ','],['),' ',',') + ']'
WHEN 'MULTILINESTRING' THEN
'"type": "MultiLineString","coordinates":' +
'[' + REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(@geo.ToString(),'MULTILINESTRING ',''),'(','['),')',']'),'], ',']],['),', ','],['),' ',',') + ']'
WHEN 'MULTIPOINT' THEN
'"type": "MultiPoint","coordinates":' +
REPLACE( REPLACE(REPLACE(REPLACE(REPLACE(@geo.ToString(),'MULTIPOINT ',''),'(','['),')',']'),' ',','),',,',', ')
WHEN 'LINESTRING' THEN
'"type": "LineString","coordinates":' +
'[' + REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(@geo.ToString(),'LINESTRING ',''),'(','['),')',']'),'], ',']],['),', ','],['),' ',',') + ']'
ELSE NULL
END)
+'}')
END
GO

空间数据类型（几何）TO GeoJSON

4 个答案: