We're running MapServer with a map that has just one layer, political boundaries from a SHP file. This layer is using a basic EPSG:4326 projection, and the map itself is using EPSG:3857. The resulting images generated by MapServer CGI queries have horizontal lines at certain latitudes:
Beyond this problem, the map is okay and lines up perfectly with the Open Street Map in OpenLayers. The MAPFILE we're using:
MAP WEB METADATA "wms_title" "Map Server" "wms_enable_request" "*" "wms_srs" "EPSG:3857" END END PROJECTION "init=epsg:3857" END IMAGETYPE PNG EXTENT -20037508.34 -20037508.34 20037508.34 20037508.34 SIZE 400 300 SHAPEPATH "../data" IMAGECOLOR 71 245 242 LAYER # States polygon layer begins here NAME Borders DATA ne_10m_admin_1_states_provinces_shp STATUS OFF TYPE POLYGON PROJECTION "init=epsg:4326" END CLASS NAME "Borders" STYLE COLOR 43 156 51 OUTLINECOLOR 32 32 32 END END END # States polygon layer ends here END
I've verified that the proj.4 EPSG file has the proper definition of EPSG:3857, and don't understand what's happening. Any insight would be greatly appreciated.