{"id":71,"date":"2007-07-14T17:40:55","date_gmt":"2007-07-14T22:40:55","guid":{"rendered":"http:\/\/www.kralidis.ca\/blog\/2007\/07\/14\/reprojecting-in-python\/"},"modified":"2007-07-14T18:41:57","modified_gmt":"2007-07-14T23:41:57","slug":"reprojecting-in-python","status":"publish","type":"post","link":"https:\/\/www.kralidis.ca\/blog\/2007\/07\/14\/reprojecting-in-python\/","title":{"rendered":"Reprojecting in Python"},"content":{"rendered":"

My previous post<\/a> declared my plugging my nose and jumping into Python GIS stuff. Advice <\/a>and info<\/a> from Sean<\/a> have been valuable in getting familiar with things, though I’ll be the first to admit I’m still green (writing Python like a Perl \/ C hack \ud83d\ude42 ).<\/p>\n

So here’s one of my first attempts at solving a real world problem: reprojecting a bunch of points from a CSV file:<\/p>\n

\r\n#!\/usr\/bin\/python<\/pre>\n
import sys\r\nimport mapscript\r\n\r\nif (len(sys.argv) == 1):<\/pre>\n
\tprint sys.argv[0] + \" <csvfile>\"\r\n\tsys.exit(1)\r\nelse:\r\n\tprojInObj  = mapscript.projectionObj(\"init=epsg:32619\")\r\n\tprojOutObj = mapscript.projectionObj(\"init=epsg:4326\")<\/pre>\n
\tprint \"id,geom,zone\"\r\n\tf = open(sys.argv[1], 'r')\r\n\tfor line in f:\r\n\t\ts = line.strip()\r\n\t\tk = s.split(\",\")\r\n\t\twkt = \"POINT(\" + k[1] + \" \" + k[2] + \")\"\r\n\t\tshape = mapscript.shapeObj.fromWKT(wkt) # man, I love WKT!!\r\n\t\tshape.project(projInObj, projOutObj)\r\n\t\tprint k[0] + \",\" + shape.toWKT() + \",\" + k[3]\r\n\tf.close()<\/pre>\n
And that’s it!  So now you can take the CSV output with the geometry encoded as WKT and hook it up to MapServer<\/a> with some simple OGR OVF syntax in your mapfile:<\/p>\n
\r\nCONNECTIONTYPE OGR\r\nCONNECTION \"<OGRVRTDataSource>\r\n<OGRVRTLayer name='nb'>\r\n<SrcDataSource>.\/nb.csv<\/SrcDataSource>\r\n<GeometryType>wkbPoint<\/GeometryType>\r\n<GeometryField encoding='WKT' field='geom'\/>\r\n<\/OGRVRTLayer>\r\n<\/OGRVRTDataSource>\"<\/pre>\n
Mind you, you might question why to reproject when MapServer can do this for you, but I digress.  There’s probably more eloquent ways to do this than what’s been done above via mapscript<\/a>, eh?<\/p>\n\n\n