diff --git a/modules/gmt/modgmt_structs.h b/modules/gmt/modgmt_structs.h
index a33d58a..85fba8d 100644
--- a/modules/gmt/modgmt_structs.h
+++ b/modules/gmt/modgmt_structs.h
@@ -117,7 +117,8 @@ struct gmt_coord: public gmt_struct
   if(isdeg) return (d+(m+s/60.0)/60.0)*(sign?1:-1);
   else return r;
  }
- bool Convert(const std::string& str)
+
+ bool Convert(const std::string& str, std::string& err)
  {
   WordList wl;
   WordList::const_iterator cw;
@@ -125,34 +126,37 @@ struct gmt_coord: public gmt_struct
   if(1==wl.size()) // No dd:mm
   {
    isdeg=false;
-   return str2double(str,&r);
+   bool res=str2double(str,&r);
+   if(!res) err="Can't convert string "+str+" to double value";
+   return res;
   }
-  if(0==wl.size() || wl.size()>3) return false;
+  if(0==wl.size() || wl.size()>3) {err="String "+str+" have incorrect format for geographic coordinate, must be ddd[:mm[:ss[.fff]]]"; return false;}
 
   isdeg=true;
   int64_t res;
 
   // degrees
   cw=wl.begin();
-  if(!str2int(*cw,&res)) return false;
+  if(!str2int(*cw,&res)) {err="Can't convert "+*cw+" to integer"; return false;}
   if(res>360 || res<-360) res%=360;
   sign=(std::string::npos==cw->find('-'));
   d=static_cast<uint16_t>(sign?res:-res);
   // minutes
   cw++;
-  if(!str2int(*cw,&res)) return false;
-  if(res<0 || res>=60) return false;
+  if(!str2int(*cw,&res)) {err="Can't convert "+*cw+" to integer"; return false;}
+  if(res<0 || res>=60) {err="Minutes must be not lesser then 0 and lesser then 60"; return false;}
   m=static_cast<uint8_t>(res);
   s=0;
 
   // seconds
   cw++;
   if(wl.end()==cw) return true; // No seconds
-  if(!str2double(*cw,&s) ) return false;
-  if(s<0.0 || s>=60.0) return false;
+  if(!str2double(*cw,&s) ) {err="Can't convert "+*cw+" to double"; return false;}
+  if(s<0.0 || s>=60.0) {err="Seconds must be not lesser then 0 and lesser then 60"; return false;}
   return true;
  }
- bool Convert(double num)
+
+ bool Convert(double num, std::string& err)
  {
   isdeg=false;
   r=num;
@@ -182,24 +186,25 @@ struct gmt_region: public gmt_struct
 
  // Only "global", "global180" and "global360"
  // TODO: add parsing of "-R" strings
- bool Convert(const std::string& istr)
+ bool Convert(const std::string& istr, std::string& err)
  {
   std::string str=istr;
   tolower(str);
   if("global180"==str)
   {
    type=GLOBAL180;
-   xb.Convert(-180.0); xe.Convert(180.0);
-   yb.Convert(-90.0); ye.Convert(90.0);
+   xb.Convert(-180.0,err); xe.Convert(180.0,err);
+   yb.Convert(-90.0,err); ye.Convert(90.0,err);
    return true;
   }
   if("global360"==str || "global"==str)
   {
    type=GLOBAL360;
-   xb.Convert(0.0); xe.Convert(360.0);
-   yb.Convert(-90.0); ye.Convert(90.0);
+   xb.Convert(0.0,err); xe.Convert(360.0,err);
+   yb.Convert(-90.0,err); ye.Convert(90.0,err);
    return true;
   }
+  err="Can't convert "+istr+" to region.";
   return false;
  }