NAME

       shprewind - validates and resets the winding order of rings

SYNOPSIS

       shprewind in_shp_file out_shp_file

DESCRIPTION

       Validates  and  resets  the  winding  order  of  rings  in polygon geometries to match the
       ordering required by  shapefile  specification.  This  is  useful  for  shapefiles  having
       troubles when checked with a ´shpdump -validate´.

       Makes  a  copy  of  the shapefile in_shp_file to out_shp_file and fixes the orientation of
       points in the rings of Polygon, PolygonZ, and PolygonM typed  shapes  to  conform  to  the
       shapefile  specification.  According  to  the  specification,  the vertices of outer rings
       should be oriented clockwise on the X/Y plane, and those of inner rings counterclockwise.

       Shapefiles actually consist of two files with the same basename and  extensions  .shp  and
       .shx  (or .SHP and .SHX) containing the shape data and shape index respectively. The files
       to open are determined by first stripping any  filename  extension  from  in_shp_file  and
       attempting  to  open  the files in_shp_file.shp or in_shp_file.SHP, and in_shp_file.shx or
       in_shp_file.SHX for the respective  data  and  index  files.  The  files  to  create  from
       out_shp_file  are  determined  by  stripping  any filename extension from out_shp_file and
       appending .shp and .shx suffixes for the respective data and index files.

OPTIONS

       in_shp_file
              the name of an existing shapefile.

       out_shp_file
              the name of the new fixed shapefile that will be created.

EXIT STATUS

       0      Successful program execution.

       1      Missing in_shp_file or out_shp_file arguments, failed to open shapefile in_shp_file
              or create shapefile out_shp_file.

DIAGNOSTICS

       The following diagnostics may be issued on stdout:

       Unable to open:in_shp_file

       Unable to create:out_shp_file

       count objects rewound.

EXAMPLE

       shprewind badshapefile newshapefile

AUTHOR

       shprewind  is  part  of shapelib, maintained by Frank Warmerdam. This guide was created by
       Eduardo Patoo Kanegae and converted to manpage by  Johan  Van  de  Wauw.  It  was  further
       enhanced with the man page written by Joonas Pihlaja (jpihlaja@cc.helsinki.fi).

BUGS

       The  implementation assumes that there is at most one outer ring in each shape, that it is
       the first ring in a shape, and all other rings in a shape are inner rings. Polygons inside
       MultiPatch shape types aren´t rewound.

SEE ALSO

       dbfadd(1),   dbfcat(1),   dbfcreate(1),   dbfdump(1),  dbfinfo(1),  shpadd(1),  shpcat(1),
       shpcentrd(1), shpcreate(1),  shpdump(1),  shpdxf(1),  shpfix(1),  shpinfo(1),  shpproj(1),
       shptest(1)

                                            April 2020                               SHPREWIND(1)