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I parse your exotic projection representations and try to figure out WTF they are + magic detection of spherical mercator and wgs84 variants
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mapbox/node-srs
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This module tries to detect projections, also known as "spatial reference systems". It works similiarly togdalsrsinfo.
node-srs supports parsing a variety of textual representations of projections, like the formats known asOGC WKT,ESRI WKT,OGC CRS URN, orproj4. It supportsshapefiles andGeoJSON. Shapefiles optionally come with a separate .prj and inside the.prj the text is usually in theESRI WKT format. GeoJSON optionally contains acrs property that declares projection asOGC CRS URN.
Detecting projections is important for applications like TileMill, which - through Mapnik - needs theproj4 representation of a projection to create coordinate transformations for re-projecting vector or raster data on the fly.
node-srs includes a variety of hacks to determine if your projection looks likeweb mercator (epsg:3857) orwgs84 (epsg:4326) and if so returns the canonical representations of these projections (according to @springmeyer). This ensures applications like TileMill can avoid unneeded projection. It is common for data out in the wild in web mercator projection to store slightly different projection strings based on the software that created the files.node-srs ensures a consistent finalproj4 representation is returned for all of the variety of representations of web mercator. This is critical because even mercator to mercator transformations are expensive if proj4 is asked to do this for large datasets.
node-srs does not support looking for, or detecting, projection information in formats like GeoTIFF, PostGIS, or SQLite. Rather for those formats you would need to extract the projection information yourself and then pass it tonode-srs.
Parse a string of projection specification data and return an object describingthe detected projection. If the SRS cannot be parsed, throws aTypeErrordescribing the issue.
Detect a proj4 literal string as spherical mercator:
>varsrs=require('srs');>srs.parse('+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs'){proj4:'+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over',srid:3857,auth:'EPSG',pretty_wkt:'PROJCS["WGS 84 / Pseudo-Mercator",\n GEOGCS["WGS 84",\n DATUM["WGS_1984",\n SPHEROID["WGS 84",6378137,298.257223563,\n AUTHORITY["EPSG","7030"]],\n AUTHORITY["EPSG","6326"]],\n PRIMEM["Greenwich",0,\n AUTHORITY["EPSG","8901"]],\n UNIT["degree",0.0174532925199433,\n AUTHORITY["EPSG","9122"]],\n AUTHORITY["EPSG","4326"]],\n UNIT["metre",1,\n AUTHORITY["EPSG","9001"]],\n PROJECTION["Mercator_1SP"],\n PARAMETER["central_meridian",0],\n PARAMETER["scale_factor",1],\n PARAMETER["false_easting",0],\n PARAMETER["false_northing",0],\n EXTENSION["PROJ4","+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs"],\n AUTHORITY["EPSG","3857"],\n AXIS["X",EAST],\n AXIS["Y",NORTH]]',esri:false,name:'Google Maps Global Mercator',valid:true,is_geographic:false,input:'+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs'}
Detect a WKT string as WGS84:
>srs.parse('GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]]'){input:'GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]]',proj4:'+proj=longlat +ellps=WGS84 +no_defs',srid:4326,auth:'EPSG',pretty_wkt:'GEOGCS["GCS_WGS_1984",\n DATUM["D_WGS_1984",\n SPHEROID["WGS_1984",6378137,298.257223563]],\n PRIMEM["Greenwich",0],\n UNIT["Degree",0.017453292519943295],\n AUTHORITY["EPSG","4326"]]',esri:false,name:'GCS_WGS_1984',valid:true,is_geographic:true}
npm installnpm testBSD, see LICENSE.txt
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I parse your exotic projection representations and try to figure out WTF they are + magic detection of spherical mercator and wgs84 variants