newbie postgis and google maps question
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newbie postgis and google maps question
by Sam Boggess
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Hello,
I'm new to PostGIS and this has to be a cakewalk for you experienced users, but your help would be greatly appreciated. I have a PostGIS enabled database that contains polygon data from a shapefile using SRID 4326. All I want to do at this point is mark the centers of all of my polygons in Google Maps. I've written my query, and it works great: select astext(centroid(poly)) from zones returns (a bunch of): POINT(-13057223.7425678 6208110.75868711) However, I have no idea what to do with this point data. Google maps expects lat and long; how can i convert this? In another forum a user suggested dividing by 10, but that's a point in Northern Canada, this point should be in NE Washington State. Any Help would be greatly appreciated |
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Re: newbie postgis and google maps question
by Paul Ramsey
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Your original data is probably not 4326. Do you have any clue what
projection it is in? Where did you get it from? P On Jan 20, 2008, at 7:02 PM, Sam Boggess wrote: > > Hello, > > I'm new to PostGIS and this has to be a cakewalk for > you experienced users, but your help would be greatly appreciated. I > have a PostGIS enabled database that contains polygon data from a > shapefile using SRID 4326. All I want to do at this point is mark the > centers of all of my polygons in Google Maps. I've written my > query, and it works great: > > select astext(centroid(poly)) > from zones > > returns (a bunch of): > POINT(-13057223.7425678 6208110.75868711) > > However, I have no idea what to do with this point data. Google maps > expects lat and long; how can i convert this? In another forum a user > suggested dividing by 10, but that's a point in Northern Canada, > this point > should be in NE Washington State. > > Any Help would be greatly appreciated > -- > View this message in context: http://www.nabble.com/newbie-postgis-and-google-maps-question-tp14989995p14989995.html > Sent from the PostGIS - User mailing list archive at Nabble.com. > > _______________________________________________ > postgis-users mailing list > postgis-users@... > http://postgis.refractions.net/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list postgis-users@... http://postgis.refractions.net/mailman/listinfo/postgis-users |
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Re: newbie postgis and google maps question
by Sam Boggess
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The original shape file, that I got from the Oregon Forestry Department, had this projection:
Data Type: Shapefile Feature Class Shapefile: Z:\FSN\seedzone_pre1996\sz_orwa_pre1996.shp Geometry Type: Polygon Projected Coordinate System: NAD_1983_Oregon_Statewide_Lambert_Feet_Intl Projection: Lambert_Conformal_Conic False_Easting: 1312335.95800525 False_Northing: 0.00000000 Central_Meridian: -120.50000000 Standard_Parallel_1: 43.00000000 Standard_Parallel_2: 45.50000000 Latitude_Of_Origin: 41.75000000 Linear Unit: Foot Geographic Coordinate System: GCS_North_American_1983 Datum: D_North_American_1983 Prime Meridian: 0 Angular Unit: Degree So I projected that into mercator in ArcMap: Data Type: Shapefile Feature Class Shapefile: Z:\FSN\seedzone_pre1996\sz_orwa_pre1996_Project.shp Geometry Type: Polygon Projected Coordinate System: World_Mercator Projection: Mercator False_Easting: 0.00000000 False_Northing: 0.00000000 Central_Meridian: 0.00000000 Standard_Parallel_1: 0.00000000 Linear Unit: Meter Geographic Coordinate System: GCS_WGS_1984 Datum: D_WGS_1984 Prime Meridian: 0 Angular Unit: Degree I then used shp2pgsql to add this to my database: SELECT AddGeometryColumn('members_oldzone', 'poly', 4326, 'MULTIPOLYGON', 2); ALTER TABLE "members_oldzone" ALTER "poly" SET NOT NULL; CREATE INDEX "members_oldzone_poly_id" ON "members_oldzone" USING GIST ( "poly" GIST_GEOMETRY_OPS );
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Re: newbie postgis and google maps question
by Paul Ramsey
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Mercator <> EPSG:4326
4326 is geographic coordinates on a WGS84 spheroid. Mercator is projected coordinates still. Either upload your shape file in the original coordinates, and then transform in PostGIS: shp2pgsql -D -i -s 2992 shpfile.shp tablename select ST_AsText(ST_Transform(the_geom, 4326)) from tablename Or do you ArcMap stuff but output in 4326 to start with. Good luck! P. On Jan 20, 2008, at 7:39 PM, Sam Boggess wrote: > > The original shape file, that I got from the Oregon Forestry > Department, had > this projection: > > Data Type: Shapefile Feature Class > Shapefile: Z:\FSN\seedzone_pre1996\sz_orwa_pre1996.shp > Geometry Type: Polygon > > Projected Coordinate System: > NAD_1983_Oregon_Statewide_Lambert_Feet_Intl > Projection: Lambert_Conformal_Conic > False_Easting: 1312335.95800525 > False_Northing: 0.00000000 > Central_Meridian: -120.50000000 > Standard_Parallel_1: 43.00000000 > Standard_Parallel_2: 45.50000000 > Latitude_Of_Origin: 41.75000000 > Linear Unit: Foot > > Geographic Coordinate System: GCS_North_American_1983 > Datum: D_North_American_1983 > Prime Meridian: 0 > Angular Unit: Degree > > > So I projected that into mercator in ArcMap: > > Data Type: Shapefile Feature Class > Shapefile: Z:\FSN\seedzone_pre1996\sz_orwa_pre1996_Project.shp > Geometry Type: Polygon > > Projected Coordinate System: World_Mercator > Projection: Mercator > False_Easting: 0.00000000 > False_Northing: 0.00000000 > Central_Meridian: 0.00000000 > Standard_Parallel_1: 0.00000000 > Linear Unit: Meter > > Geographic Coordinate System: GCS_WGS_1984 > Datum: D_WGS_1984 > Prime Meridian: 0 > Angular Unit: Degree > > > I then used shp2pgsql to add this to my database: > > SELECT AddGeometryColumn('members_oldzone', 'poly', 4326, > 'MULTIPOLYGON', > 2); > ALTER TABLE "members_oldzone" ALTER "poly" SET NOT NULL; > CREATE INDEX "members_oldzone_poly_id" ON "members_oldzone" USING > GIST ( > "poly" GIST_GEOMETRY_OPS ); > > > > Paul Ramsey wrote: >> >> Your original data is probably not 4326. Do you have any clue what >> projection it is in? Where did you get it from? >> >> P >> >> On Jan 20, 2008, at 7:02 PM, Sam Boggess wrote: >> >>> >>> Hello, >>> >>> I'm new to PostGIS and this has to be a cakewalk for >>> you experienced users, but your help would be greatly >>> appreciated. I >>> have a PostGIS enabled database that contains polygon data from a >>> shapefile using SRID 4326. All I want to do at this point is mark >>> the >>> centers of all of my polygons in Google Maps. I've written my >>> query, and it works great: >>> >>> select astext(centroid(poly)) >>> from zones >>> >>> returns (a bunch of): >>> POINT(-13057223.7425678 6208110.75868711) >>> >>> However, I have no idea what to do with this point data. Google >>> maps >>> expects lat and long; how can i convert this? In another forum a >>> user >>> suggested dividing by 10, but that's a point in Northern Canada, >>> this point >>> should be in NE Washington State. >>> >>> Any Help would be greatly appreciated >>> -- >>> View this message in context: >>> http://www.nabble.com/newbie-postgis-and-google-maps-question-tp14989995p14989995.html >>> Sent from the PostGIS - User mailing list archive at Nabble.com. >>> >>> _______________________________________________ >>> postgis-users mailing list >>> postgis-users@... >>> http://postgis.refractions.net/mailman/listinfo/postgis-users >> >> _______________________________________________ >> postgis-users mailing list >> postgis-users@... >> http://postgis.refractions.net/mailman/listinfo/postgis-users >> >> > > -- > View this message in context: http://www.nabble.com/newbie-postgis-and-google-maps-question-tp14989995p14990735.html > Sent from the PostGIS - User mailing list archive at Nabble.com. > > _______________________________________________ > postgis-users mailing list > postgis-users@... > http://postgis.refractions.net/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list postgis-users@... http://postgis.refractions.net/mailman/listinfo/postgis-users |
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Re: newbie postgis and google maps question
by Sam Boggess
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Thank you so much! I'll try transforming it at the shp2pgsql stage.
In ArcMap does 4326 have a name? I can't find it?
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Re: newbie postgis and google maps question
by Paul Ramsey
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"Geographic Coordinates", "Longitude / Latitude", "Unprojected" ?
P. On Jan 20, 2008, at 8:07 PM, Sam Boggess wrote: > > Thank you so much! I'll try transforming it at the shp2pgsql stage. > > In ArcMap does 4326 have a name? I can't find it? > > > > Paul Ramsey wrote: >> >> Mercator <> EPSG:4326 >> >> 4326 is geographic coordinates on a WGS84 spheroid. Mercator is >> projected coordinates still. >> >> Either upload your shape file in the original coordinates, and then >> transform in PostGIS: >> >> shp2pgsql -D -i -s 2992 shpfile.shp tablename >> select ST_AsText(ST_Transform(the_geom, 4326)) from tablename >> >> Or do you ArcMap stuff but output in 4326 to start with. >> >> Good luck! >> >> P. >> >> On Jan 20, 2008, at 7:39 PM, Sam Boggess wrote: >> >>> >>> The original shape file, that I got from the Oregon Forestry >>> Department, had >>> this projection: >>> >>> Data Type: Shapefile Feature Class >>> Shapefile: Z:\FSN\seedzone_pre1996\sz_orwa_pre1996.shp >>> Geometry Type: Polygon >>> >>> Projected Coordinate System: >>> NAD_1983_Oregon_Statewide_Lambert_Feet_Intl >>> Projection: Lambert_Conformal_Conic >>> False_Easting: 1312335.95800525 >>> False_Northing: 0.00000000 >>> Central_Meridian: -120.50000000 >>> Standard_Parallel_1: 43.00000000 >>> Standard_Parallel_2: 45.50000000 >>> Latitude_Of_Origin: 41.75000000 >>> Linear Unit: Foot >>> >>> Geographic Coordinate System: GCS_North_American_1983 >>> Datum: D_North_American_1983 >>> Prime Meridian: 0 >>> Angular Unit: Degree >>> >>> >>> So I projected that into mercator in ArcMap: >>> >>> Data Type: Shapefile Feature Class >>> Shapefile: Z:\FSN\seedzone_pre1996\sz_orwa_pre1996_Project.shp >>> Geometry Type: Polygon >>> >>> Projected Coordinate System: World_Mercator >>> Projection: Mercator >>> False_Easting: 0.00000000 >>> False_Northing: 0.00000000 >>> Central_Meridian: 0.00000000 >>> Standard_Parallel_1: 0.00000000 >>> Linear Unit: Meter >>> >>> Geographic Coordinate System: GCS_WGS_1984 >>> Datum: D_WGS_1984 >>> Prime Meridian: 0 >>> Angular Unit: Degree >>> >>> >>> I then used shp2pgsql to add this to my database: >>> >>> SELECT AddGeometryColumn('members_oldzone', 'poly', 4326, >>> 'MULTIPOLYGON', >>> 2); >>> ALTER TABLE "members_oldzone" ALTER "poly" SET NOT NULL; >>> CREATE INDEX "members_oldzone_poly_id" ON "members_oldzone" USING >>> GIST ( >>> "poly" GIST_GEOMETRY_OPS ); >>> >>> >>> >>> Paul Ramsey wrote: >>>> >>>> Your original data is probably not 4326. Do you have any clue what >>>> projection it is in? Where did you get it from? >>>> >>>> P >>>> >>>> On Jan 20, 2008, at 7:02 PM, Sam Boggess wrote: >>>> >>>>> >>>>> Hello, >>>>> >>>>> I'm new to PostGIS and this has to be a cakewalk for >>>>> you experienced users, but your help would be greatly >>>>> appreciated. I >>>>> have a PostGIS enabled database that contains polygon data from a >>>>> shapefile using SRID 4326. All I want to do at this point is mark >>>>> the >>>>> centers of all of my polygons in Google Maps. I've written my >>>>> query, and it works great: >>>>> >>>>> select astext(centroid(poly)) >>>>> from zones >>>>> >>>>> returns (a bunch of): >>>>> POINT(-13057223.7425678 6208110.75868711) >>>>> >>>>> However, I have no idea what to do with this point data. Google >>>>> maps >>>>> expects lat and long; how can i convert this? In another forum a >>>>> user >>>>> suggested dividing by 10, but that's a point in Northern Canada, >>>>> this point >>>>> should be in NE Washington State. >>>>> >>>>> Any Help would be greatly appreciated >>>>> -- >>>>> View this message in context: >>>>> http://www.nabble.com/newbie-postgis-and-google-maps-question-tp14989995p14989995.html >>>>> Sent from the PostGIS - User mailing list archive at Nabble.com. >>>>> >>>>> _______________________________________________ >>>>> postgis-users mailing list >>>>> postgis-users@... >>>>> http://postgis.refractions.net/mailman/listinfo/postgis-users >>>> >>>> _______________________________________________ >>>> postgis-users mailing list >>>> postgis-users@... >>>> http://postgis.refractions.net/mailman/listinfo/postgis-users >>>> >>>> >>> >>> -- >>> View this message in context: >>> http://www.nabble.com/newbie-postgis-and-google-maps-question-tp14989995p14990735.html >>> Sent from the PostGIS - User mailing list archive at Nabble.com. >>> >>> _______________________________________________ >>> postgis-users mailing list >>> postgis-users@... >>> http://postgis.refractions.net/mailman/listinfo/postgis-users >> >> _______________________________________________ >> postgis-users mailing list >> postgis-users@... >> http://postgis.refractions.net/mailman/listinfo/postgis-users >> >> > > -- > View this message in context: http://www.nabble.com/newbie-postgis-and-google-maps-question-tp14989995p14990938.html > Sent from the PostGIS - User mailing list archive at Nabble.com. > > _______________________________________________ > postgis-users mailing list > postgis-users@... > http://postgis.refractions.net/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list postgis-users@... http://postgis.refractions.net/mailman/listinfo/postgis-users |
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