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1

An SRID is a coordinate system. We're taught in (traditional / Arc) "GIS" to always store your data in a projected coordinate system, because we're going to eventually use some calculation like 'area', so we'd better store our data in a coordinate system that gives us that measurement. However, PostGIS throws that concept out the window. Here's a good ...


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EPSG.io offers a more modern interface to explore EPSG codes and their porperties. http://epsg.io/2100


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Usually, the unit is given for each CRS inside its documentation, so you can find it directly in the CRS information, for example : UNIT["metre",1,AUTHORITY["EPSG","9001"] UNIT["degree",0.01745329251994328, AUTHORITY["EPSG","9122"]] if you don't find the information on your system (, you can check on spatialreference.org Be aware that sometimes ...


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You can look up your CRS under http://spatialreference.org/ref/epsg/2100/ Following the first link, you will find: UNIT["metre",1, AUTHORITY["EPSG","9001"]], You will get the same information when you look up the code definition in the spatial_ref_sys table of your postgis database. There it looks like +proj=tmerc +lat_0=0 +lon_0=24 +k=0.9996 ...


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the jsapi is smart enough to be able to reproject WGS84 geometries added to the map on the fly internally and display them in web mercator {wkid:3857} applications. check out esri/geometry/webMercatorUtils for a look at clientside methods that help you do the same on your own. if you need to reproject between other coordinate systems you'll either need ...


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You could use the information here to generate a SRID - basically add the zone number to 32600 (in the north) and 32700 in the south. This works if you can use WGS84 as the geographic coordinate reference system. The utm_zone_letter identifies the latitude band. If the data is always in the northern hemisphere, then you could ignore it and use 32600 + ...


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You'll need to translate the UTM zone to an EPSG code, use ST_FromText to create a geometry object in that projection, and then use ST_Transform to transform your geometry object into whatever SRID you are using for the entire table. I haven't tried it, but this link gives a description of how to programatically convert from latitude/longitude to UTM zone; ...


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I think you should be able to use this function (from here): -- Function: utmzone(geometry) -- DROP FUNCTION utmzone(geometry); -- Usage: SELECT ST_Transform(the_geom, utmzone(ST_Centroid(the_geom)) ) FROM sometable; CREATE OR REPLACE FUNCTION utmzone(geometry) RETURNS integer AS $BODY$ DECLARE geomgeog geometry; zone int; pref ...


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The term "SRID" is overloaded in the GIS realm. In most contexts it refers to the coordinate reference system (CRS) of spatial data, but in Esri use, it really does refer to the spatial reference system, which is a combination of CRS with the X, Y, Z, and M offsets, X/Y, Z, and M scaling factors, the precision (HIGH or BASIC), the cluster tolerances (which ...


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The database will accept any value for the x,y, and srid. The srid is just like the .prj file and is just metadata about what coordinate system the data should be. Esri stores this coordinate system metadata in the sde_spatial_references table. You would be able to store GCS coordinates in a projected srid. Your data just wouldn't line up with properly ...



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