ST_Transform
Föregående  11.7. Raster-redigerare  Nästa

Namn

ST_Transform — Återprojicerar ett raster i ett känt spatialt referenssystem till ett annat känt spatialt referenssystem med hjälp av en angiven omsamplingsalgoritm. Alternativen är NearestNeighbor, Bilinear, Cubic, CubicSpline, Lanczos med NearestNeighbor som standard.

Synopsis

raster ST_Transform(raster rast, integer srid, text algorithm=NearestNeighbor, double precision maxerr=0.125, double precision scalex, double precision scaley);

raster ST_Transform(raster rast, integer srid, double precision scalex, double precision scaley, text algorithm=NearestNeighbor, double precision maxerr=0.125);

raster ST_Transform(raster rast, raster alignto, text algorithm=NearestNeighbor, double precision maxerr=0.125);

Description

Återprojicerar ett raster i ett känt spatialt referenssystem till ett annat känt spatialt referenssystem med hjälp av en angiven pixelwarpingalgoritm. Använder "NearestNeighbor" om ingen algoritm har angetts och maxerror procent på 0,125 om ingen maxerr har angetts.

Algoritmalternativen är: "NearestNeighbor", "Bilinear", "Cubic", "CubicSpline" och "Lanczos". Hänvisa till: GDAL Warp resampling methods för mer information.

ST_Transform förväxlas ofta med ST_SetSRID(). ST_Transform ändrar faktiskt koordinaterna för ett raster (och omsamplar pixelvärdena) från ett spatialt referenssystem till ett annat, medan ST_SetSRID() helt enkelt ändrar SRID-identifieraren för rastret.

Till skillnad från de andra varianterna kräver variant 3 ett referensraster som alignto. Det transformerade rastret kommer att transformeras till referensrastrets spatiala referenssystem (SRID) och anpassas (ST_SameAlignment = TRUE) till referensrastret.

[Notera]

If you find your transformation support is not working right, you may need to set the environment variable PROJSO to the projection library your PostGIS build is using. This just needs to have the name of the file. So for example on windows, you would in Control Panel -> System -> Environment Variables add a system variable called PROJSO and set it to libproj.dll. You'll have to restart your PostgreSQL service/daemon after this change.

[Varning]

När du omvandlar en täckning av plattor vill du nästan alltid använda ett referensraster för att säkerställa samma inriktning och inga luckor i dina plattor, vilket visas i exemplet: Variant 3.

Tillgänglighet: 2.0.0 Kräver GDAL 1.6.1+

Förbättrad: 2.1.0 Tillägg av ST_Transform(rast, alignto)-variant

Exempel

Compare a source raster with nearest-neighbor and bilinear reprojections. The diagonal bands make the resampling behavior visible: nearest-neighbor keeps hard pixel steps, while bilinear smooths values between pixels. All three figures are generated from this query at manual build time.

Code
WITH rows AS (
    SELECT
        y,
        array_agg(
            ((
                    x * 3 + y * 5
                    + CASE WHEN (x + y) % 8 < 4 THEN 80 ELSE 0 END
                ) % 255)::double precision
            ORDER BY x
        ) AS row_values
    FROM generate_series(1, 80) AS y
    CROSS JOIN generate_series(1, 80) AS x
    GROUP BY y
), source AS (
    SELECT ST_SetValues(
        ST_AddBand(
            ST_MakeEmptyRaster(
                80, 80,
                -500000, 600000,
                2500, -2500,
                0, 0,
                2163
            ),
            1, '8BUI', 0, NULL
        ),
        1, 1, 1,
        array_agg(row_values ORDER BY y)::double precision[][]
    ) AS rast
    FROM rows
), transformed AS (
    SELECT
        rast,
        ST_Transform(rast, 4326, 'NearestNeighbor') AS nearest,
        ST_Transform(rast, 4326, 'Bilinear') AS bilinear
    FROM source
)
SELECT
    ST_AsPNG(rast) AS "source (EPSG:2163)",
    ST_AsPNG(nearest) AS "nearest (EPSG:4326)",
    ST_AsPNG(bilinear) AS "bilinear (EPSG:4326)"
FROM transformed;
Rasterutdata
PNG image, 80 x 80 pixels | PNG image, 98 x 64 pixels | PNG image, 98 x 64 pixels
Figure
Geometry figure for visual-rt-st-transform-01

Raster reprojection and resampling.

Massachusetts State Plane source

WGS 84 nearest-neighbor

WGS 84 bilinear

Variant 3.

Följande visar skillnaden mellan att använda ST_Transform(raster, srid) och ST_Transform(raster, alignto)

Code
WITH foo AS (
    SELECT 0 AS rid, ST_AddBand(ST_MakeEmptyRaster(2, 2, -500000, 600000, 100, -100, 0, 0, 2163), 1, '16BUI', 1, 0) AS rast UNION ALL
    SELECT 1, ST_AddBand(ST_MakeEmptyRaster(2, 2, -499800, 600000, 100, -100, 0, 0, 2163), 1, '16BUI', 2, 0) AS rast UNION ALL
    SELECT 2, ST_AddBand(ST_MakeEmptyRaster(2, 2, -499600, 600000, 100, -100, 0, 0, 2163), 1, '16BUI', 3, 0) AS rast UNION ALL

    SELECT 3, ST_AddBand(ST_MakeEmptyRaster(2, 2, -500000, 599800, 100, -100, 0, 0, 2163), 1, '16BUI', 10, 0) AS rast UNION ALL
    SELECT 4, ST_AddBand(ST_MakeEmptyRaster(2, 2, -499800, 599800, 100, -100, 0, 0, 2163), 1, '16BUI', 20, 0) AS rast UNION ALL
    SELECT 5, ST_AddBand(ST_MakeEmptyRaster(2, 2, -499600, 599800, 100, -100, 0, 0, 2163), 1, '16BUI', 30, 0) AS rast UNION ALL

    SELECT 6, ST_AddBand(ST_MakeEmptyRaster(2, 2, -500000, 599600, 100, -100, 0, 0, 2163), 1, '16BUI', 100, 0) AS rast UNION ALL
    SELECT 7, ST_AddBand(ST_MakeEmptyRaster(2, 2, -499800, 599600, 100, -100, 0, 0, 2163), 1, '16BUI', 200, 0) AS rast UNION ALL
    SELECT 8, ST_AddBand(ST_MakeEmptyRaster(2, 2, -499600, 599600, 100, -100, 0, 0, 2163), 1, '16BUI', 300, 0) AS rast
), bar AS (
    SELECT
        ST_Transform(rast, 4269) AS alignto
    FROM foo
    LIMIT 1
), baz AS (
    SELECT
        rid,
        rast,
        ST_Transform(rast, 4269) AS not_aligned,
        ST_Transform(rast, alignto) AS aligned
    FROM foo
    CROSS JOIN bar
)
SELECT
    ST_Collect(ST_ConvexHull(not_aligned) ORDER BY rid) AS not_aligned,
    ST_Collect(ST_ConvexHull(aligned) ORDER BY rid) AS aligned
FROM baz
Rasterutdata
MULTIPOLYGON(((-107.007 50.2,-107.005 50.2,-107.005 50.198,-107.007 50.198,-107.007 50.2)),((-107.004 50.201,-107.002 50.201,-107.002 50.198,-107.004 50.198,-107.004 50.201)),((-107.001 50.201,-106.999 50.201,-106.999 50.198,-107.001 50.198,-107.001 50.201)),((-107.007 50.199,-107.004 50.199,-107.004 50.196,-107.007 50.196,-107.007 50.199)),((-107.004 50.199,-107.001 50.199,-107.001 50.196,-107.004 50.196,-107.004 50.199)),((-107.001 50.199,-106.999 50.199,-106.999 50.196,-107.001 50.196,-107.001 50.199)),((-107.006 50.197,-107.004 50.197,-107.004 50.194,-107.006 50.194,-107.006 50.197)),((-107.004 50.197,-107.001 50.197,-107.001 50.194,-107.004 50.194,-107.004 50.197)),((-107.001 50.197,-106.998 50.197,-106.998 50.195,-107.001 50.195,-107.001 50.197))) | MULTIPOLYGON(((-107.007 50.2,-107.005 50.2,-107.005 50.198,-107.007 50.198,-107.007 50.2)),((-107.005 50.202,-107.001 50.202,-107.001 50.198,-107.005 50.198,-107.005 50.202)),((-107.002 50.202,-106.998 50.202,-106.998 50.198,-107.002 50.198,-107.002 50.202)),((-107.007 50.199,-107.003 50.199,-107.003 50.195,-107.007 50.195,-107.007 50.199)),((-107.005 50.199,-107.001 50.199,-107.001 50.195,-107.005 50.195,-107.005 50.199)),((-107.002 50.199,-106.998 50.199,-106.998 50.195,-107.002 50.195,-107.002 50.199)),((-107.007 50.198,-107.003 50.198,-107.003 50.194,-107.007 50.194,-107.007 50.198)),((-107.005 50.198,-107.001 50.198,-107.001 50.194,-107.005 50.194,-107.005 50.198)),((-107.002 50.198,-106.998 50.198,-106.998 50.194,-107.002 50.194,-107.002 50.198)))
Figure
Geometry figure for visual-rt-st-transform-02