diff --git a/pom.xml b/pom.xml
index 320c95d..b599314 100644
--- a/pom.xml
+++ b/pom.xml
@@ -13,7 +13,7 @@
     
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-    <java.version>11</java.version>
+    <java.version>1.8</java.version>
     <maven.compiler.source>${java.version}</maven.compiler.source>
     <maven.compiler.target>${java.version}</maven.compiler.target>
     <gpg.skip>true</gpg.skip>
@@ -39,9 +39,16 @@
     <dependency>
       <groupId>osm.surveyor</groupId>
       <artifactId>AdjustTime</artifactId>
-      <version>5.3.9</version>
+      <version>5.3.10-SNAPSHOT</version>
     </dependency>
     
+    <!-- https://mvnrepository.com/artifact/org.apache.maven.plugins/maven-compiler-plugin -->
+    <dependency>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-compiler-plugin</artifactId>
+        <version>3.8.1</version>
+    </dependency>
+
     <!-- https://mvnrepository.com/artifact/org.apache.commons/commons-imaging -->
     <dependency>
       <groupId>org.apache.commons</groupId>
diff --git a/src/main/java/osm/jp/gpx/matchtime/gui/ParameterData.java b/src/main/java/osm/jp/gpx/matchtime/gui/ParameterData.java
deleted file mode 100644
index 76eb082..0000000
--- a/src/main/java/osm/jp/gpx/matchtime/gui/ParameterData.java
+++ /dev/null
@@ -1,23 +0,0 @@
-package osm.jp.gpx.matchtime.gui;
-
-import java.util.Observable;
-
-public class ParameterData extends Observable {
-    String content = "";
-    
-    String getContent() {
-        return content;
-    }
-
-    void setContent(String content) {
-        this.content = content;
-        setChanged();
-        super.notifyObservers(content);
-        clearChanged();
-    }
-
-    @Override
-    public void notifyObservers(Object arg) {
-        setContent(arg.toString());
-    }
-}
diff --git a/src/main/java/osm/jp/gpx/matchtime/gui/ParameterPanelImageFile.java b/src/main/java/osm/jp/gpx/matchtime/gui/ParameterPanelImageFile.java
index 1956433..1b6373c 100644
--- a/src/main/java/osm/jp/gpx/matchtime/gui/ParameterPanelImageFile.java
+++ b/src/main/java/osm/jp/gpx/matchtime/gui/ParameterPanelImageFile.java
@@ -18,12 +18,12 @@
 public class ParameterPanelImageFile extends ParameterPanel implements PropertyChangeListener {
     JFileChooser fc;
     public JButton openButton;
-    public ParameterPanelFolder paramDir;
+    public ParameterPanelSourceFolder paramDir;
     private final PropertyChangeSupport pcs = new PropertyChangeSupport(this);
 
     public ParameterPanelImageFile(
             String name, String label, String text, 
-            ParameterPanelFolder paramDir
+            ParameterPanelSourceFolder paramDir
     ) {
         super(name, label, text);
 
diff --git a/src/main/java/osm/jp/gpx/matchtime/gui/ParameterPanelSourceFolder.java b/src/main/java/osm/jp/gpx/matchtime/gui/ParameterPanelSourceFolder.java
index 1230af8..be1998f 100644
--- a/src/main/java/osm/jp/gpx/matchtime/gui/ParameterPanelSourceFolder.java
+++ b/src/main/java/osm/jp/gpx/matchtime/gui/ParameterPanelSourceFolder.java
@@ -28,7 +28,11 @@
         }
         try {
             File dir = super.getDirectory();
-            return (dir.exists() && dir.isDirectory());
+			File[] files = dir.listFiles(new ImageFileFilter());
+			if ((files == null) || (files.length < 1)) {
+				return false;
+			}
+			return true;
         }
         catch (Exception e) {
             return false;
@@ -39,9 +43,8 @@
     public File getDirectory() throws FileNotFoundException {
         File dir = super.getDirectory();
         if (dir.exists() && dir.isDirectory()) {
-        	
+        	return dir;
         }
-        return dir;
+        throw new FileNotFoundException();
     }
-
 }
\ No newline at end of file