diff --git a/gmtsph-regional.sh b/gmtsph-regional.sh
index f913202..788d649 100755
--- a/gmtsph-regional.sh
+++ b/gmtsph-regional.sh
@@ -32,7 +32,7 @@ For further explanations, please look for GMT's manuscripts.\nAuthor: Yi Zhang (
 			printf "usage: ${0##*/} -i<grid-data> [-r<xmin>/<xmax>/<ymin>/<ymax>] [-u<unit>] [-c<cpt-file>] [-a<x-label>,<y-label>] [-t<x-tick>,<y-tick>] [-v<c-tick>] [-l<size>] [-b] [-g] [-n] [-p]\n"
 			printf "%s\t%s\n" "-i" "input grid file"
 			printf "%s\t%s\n" "-r" "data range. The template will detect the input data range automatically, the use of this option will overwrite the range."
-			printf "%s\t%s\n" "-u" "data unit. The default is meter."
+			printf "%s\t%s\n" "-u" "data unit. The default is meter. use 'km+Uk' to append '+Uk' option to the psscale command."
 			printf "%s\t%s\n" "-c" "color cpt. The default is rainbow. The script will use grd2cpt to recalculate the color scale file, use -n option to disable the use of grd2cpt."
 			printf "%s\t%s\n" "-a" "axis labels. The deafults are x (m) and y (m)."
 			printf "%s\t%s\n" "-t" "intervals of axis's labels. the script will set the intervals automatically if -t option is not set."
@@ -148,7 +148,7 @@ else
 
 	#-C${cptfile}+Uk 使用km（色标单位除1000
 	#如果unit等于km则在cptfile后面添加+Uk
-	if [[ ${unit} == 'km' ]]; then
+	if [[ ${unit} == 'km+Uk' ]]; then
 		gmt psscale -Dx${pagePara[1]}+w${pagePara[2]}+h -C${cptfile}+Uk -Bx${bartick} -By+l${unit} -O >> $psfile
 	else
 		gmt psscale -Dx${pagePara[1]}+w${pagePara[2]}+h -C${cptfile} -Bx${bartick} -By+l${unit} -O >> $psfile