raster-a.xml

<?xml version="1.0" encoding="utf-8"?>

<Map srs="+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" background-color="#ffffff" maximum-extent="-20037508.34,-20037508.34,20037508.34,20037508.34">

<Parameters>
  <Parameter name="bounds">-180,-85.0511,180,85.0511</Parameter>
  <Parameter name="center">0,0,2</Parameter>
  <Parameter name="minzoom">0</Parameter>
  <Parameter name="maxzoom">8</Parameter>
  <Parameter name="name"><![CDATA[raster-a]]></Parameter>
</Parameters>

<Style name="style">
    <Rule>
        <RasterSymbolizer scaling="bilinear" />
    </Rule>
</Style>

<Layer name="world" srs="+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">
    <StyleName>style</StyleName>
    <Datasource>
        <Parameter name="file">data/natural_earth.tif</Parameter>
        <Parameter name="type">gdal</Parameter>
    </Datasource>
</Layer>

</Map>