diff --git a/gmtxy-image.sh b/gmtxy-image.sh
index e27ac4d..126ac43 100755
--- a/gmtxy-image.sh
+++ b/gmtxy-image.sh
@@ -4,6 +4,7 @@
 #GMT显示平面数据脚本，输入文件为网格文件，没有包含网格化语句因为网格化过程中的情况多样化，建议在其他脚本中个别添加再调用此脚本
 # 初始化参数
 data='null'
+gridData='null'
 unit='m'
 color='rainbow'
 range='null'
@@ -12,7 +13,7 @@ overwrite=0
 labels=("x (m)" "y (m)")
 plotgrad=0
 # 从命令行获取参数
-while getopts "hi:r:u:c:a:g" arg
+while getopts "hi:r:u:c:a:G:g" arg
 do
 	case $arg in
 		h)
@@ -25,6 +26,7 @@ For futher explanations, please look for GMT's manuscripts.\nAuthor: Yi Zhang (z
 			printf "%s\t%s\n" "-c" "color cpt. The default is rainbow."
 			printf "%s\t%s\n" "-a" "axis labels. The deafults are x (m) and y (m)."
 			printf "%s\t%s\n" "-g" "use grdgradient. The default is false."
+			printf "%s\t%s\n" "-G" "provide a different input grid data for the use of grdgradient. This should be used with the '-g' option at the same time"
 			exit 0;;
 		i)
 			data=$OPTARG;;
@@ -39,6 +41,8 @@ For futher explanations, please look for GMT's manuscripts.\nAuthor: Yi Zhang (z
 			labels=(${OPTARG//,/ });;
 		g)
 			plotgrad=1;;
+		G)
+			gridData=$OPTARG;;
 		?)
 			printf "error: unknow argument\nuse -h option to see help information\n"
 			exit 1;;
@@ -70,10 +74,14 @@ else
 	MAP_FRAME_AXES=WeSnZ \
 	MAP_LABEL_OFFSET=4p
 
-	gmt grd2cpt ${data} -C${color} -Z -D > $cptfile
+	gmt grd2cpt ${data} -C${color} -R${range} -Z -D > $cptfile
 	if [[ $plotgrad == 1 ]]; then
-		gradfile=usergradient.nc
-		gmt grdgradient ${data} -G${gradfile} -Nt -A0/45
+		gradfile=${data%.*}Grad.nc
+		if [[ $gridData == 'null' ]]; then
+			gmt grdgradient ${data} -G${gradfile} -Nt -A0/45
+		else
+			gmt grdgradient ${gridData} -G${gradfile} -Nt -A0/45
+		fi
 		gmt grdimage ${data} -R${range} -C${cptfile} -I${gradfile} -Bxag+l"${labels[0]}" -Byag+l"${labels[1]}" -JX3i -K -P > $psfile
 	else
 		gmt grdimage ${data} -R${range} -C${cptfile} -Bxag+l"${labels[0]}" -Byag+l"${labels[1]}" -JX3i -K -P > $psfile