在openlayer中的图层的马赛克

Question

我正在使用mapserver和openlayers，当我绘制WMS图层时遇到问题。我得到了这一层的马赛克，我不知道为什么。有人可以帮帮我吗？我的HTML代码是：

map = new OpenLayers.Map('map', {
  controls: []
});
wms = new OpenLayers.Layer.WMS('Municipios',
  "path of the map", {
    layers: "MUNICIPIO"
  }, {
    isBaseLayer: "true",
    visibility: "true"
  });
map.addLayer(wms);
map.zoomToMaxExtent();

我的mapfile是：

MAP

NAME "mapa2"
SIZE 1400 900
IMAGETYPE png
IMAGECOLOR 196 240 255
EXTENT -16.0006 27.7281 -13.2323 29.3318
SHAPEPATH "datos"
FONTSET "path"

WEB 
    TEMPLATE "/mapserver/ms4w/apps/prueba/index.html"
    IMAGEPATH "/mapserver/ms4w/tmp/ms_tmp/"
    IMAGEURL "/ms_tmp/"
    METADATA
                "WMS_TITLE" "mapa2"
        "WMS_SRS" "EPSG:4258"
    END
END

LAYER
    NAME Foto1
    TILEINDEX indice.shp
    TILEITEM location
    DATA Foto1
    TYPE RASTER
    STATUS on
    OFFSITE 252 252 252 
    METADATA
        WMS_NAME "Foto1"
        WMS_FORMAT "IMAGE/PNG"
        WMS_SRS "EPSG:4258"
    END
END

LAYER
    NAME    "MUNICIPIO"
    STATUS  ON
    DATA    MUNICIPIO
    LABELITEM "NOM_MUNICI"
    TYPE POLYGON
    CLASS
        STYLE
            COLOR 254 226 197
            OUTLINECOLOR    255 0 0
        END
        LABEL 
            SIZE SMALL
            COLOR 0 0 0
        END
    END
END

我想放置栅格图层，但我不能。