diff --git a/kmlpng2gtiff.sh b/kmlpng2gtiff.sh
index bdde1b2615814946289f5677376dfd2b574c7d71..ee7bf35688817fdfbc3334c45af69cd16cab7e24 100755
--- a/kmlpng2gtiff.sh
+++ b/kmlpng2gtiff.sh
@@ -10,12 +10,11 @@ set -e
 
 KML=$1
 PNG=$2
+GTIFF=$3
 
-GTIFF=`echo $KML | sed s:.kml:.tif:`
-
-north=`grep "north" ${KML} | sed s:\<north\>::g | sed s:\</north\>::g`
-south=`grep "south" ${KML} | sed s:\<south\>::g | sed s:\</south\>::g`
-west=`grep "west" ${KML} | sed s:\<west\>::g | sed s:\</west\>::g`
-east=`grep "east" ${KML} | sed s:\<east\>::g | sed s:\</east\>::g`
+north=`grep "<north>" ${KML} | sed s:\<north\>::g | sed s:\</north\>::g`
+south=`grep "<south>" ${KML} | sed s:\<south\>::g | sed s:\</south\>::g`
+west=`grep "<west>" ${KML} | sed s:\<west\>::g | sed s:\</west\>::g`
+east=`grep "<east>" ${KML} | sed s:\<east\>::g | sed s:\</east\>::g`
 
 gdal_translate -of GTiff -a_ullr $west $north $east $south $PNG $GTIFF