diff --git a/gcal-import-admin.php b/gcal-import-admin.php
index 0bb4130..78e1955 100644
--- a/gcal-import-admin.php
+++ b/gcal-import-admin.php
@@ -65,6 +65,9 @@ function gcal_admin_init(){
 
     add_settings_section('gcal_geocoding', 'Geocoding', 'gcal_geocoding_section_text', 'gcal');
     add_settings_field('gcal_geocoding', 'Geocoding', 'gcal_geocoding_setting_string', 'gcal', 'gcal_geocoding');    
+
+    add_settings_section('gcal_debugging', 'Debugging', 'gcal_debugging_section_text', 'gcal');
+    add_settings_field('gcal_debugging', 'Debugging', 'gcal_debugging_setting_string', 'gcal', 'gcal_debugging');    
 }
 
 
@@ -133,7 +136,7 @@ function gcal_geocoding_setting_string() {
                     ),             
                     array( 
                         'option' => 'osm',
-                        'name' => 'OpenStreetMap - in Entwicklung',
+                        'name' => 'OpenStreetMap',
                     ),             
                 );
     
@@ -149,6 +152,22 @@ function gcal_geocoding_setting_string() {
 }
 
 
+function gcal_debugging_section_text() {
+?>
+    <p><b>Debugging aktivieren (landet in ${APACHE_LOG_DIR}/error.log).</b></p>
+<?php
+}
+
+
+
+function gcal_debugging_setting_string($args) {
+    $options = get_option('gcal_options');
+    // example from https://code.tutsplus.com/tutorials/the-wordpress-settings-api-part-8-validation-sanitisation-and-input-i--wp-25361
+    echo '<input type="checkbox" id="gcal_debugging" name="gcal_options[gcal_debugging]" value="1"' . checked( 1, $options['gcal_debugging'], false ) . '>';
+    // actual logging is done by gcal_error_log() 
+}
+
+
 
 function gcal_options_validate($input) {
     return $input; 
diff --git a/gcal-import-geocode.php b/gcal-import-geocode.php
index 40b5d5a..b8c80be 100644
--- a/gcal-import-geocode.php
+++ b/gcal-import-geocode.php
@@ -126,7 +126,7 @@ Suchen: if ( isset ( $options['geocache']['hashx'] ) ) ...
                 'gcal_geo_lon' => $lon, 
                 'gcal_geo_timestamp' => time(),
             ));
-            error_log ("INFO: geocoded and cached lat=$lat lon=$lon for location $location");
+            gcal_error_log ("INFO: geocoded and cached lat=$lat lon=$lon for location $location");
         } 
         // error handling? 
     }
@@ -138,7 +138,7 @@ function gcal_import_geocode_official($location) {
     $options = get_option('gcal_options');
     $apikey = $options['apikey'];
     if ( empty ($apikey) ) {  // ??? we should handle this in the admin frontend. 
-        error_log ("WARN: using Google official geocoding but provided no APIKEY");
+        gcal_error_log ("WARN: using Google official geocoding but provided no APIKEY");
         return array ('','');
     } else {
         $location = urlencode($location);
@@ -171,7 +171,7 @@ function gcal_import_geocode_osm($location) {
     // https://wiki.openstreetmap.org/wiki/Nominatim
     // https://nominatim.openstreetmap.org/search?q=Hotel+Gumberger+Gasthof+GmbH&format=json'
     $location = urlencode($location);
-    error_log ("gcal_import_geocode_osm: location $location");
+    gcal_error_log ("gcal_import_geocode_osm: location $location");
     // the main problem with Nominatim is that it doesn't understand GCal location information very well. 
     // we ought to cut off the location name and the country, i.e. zip code, city & street address only 
     $url = 'https://nominatim.openstreetmap.org/search?q="' . $location . '"&format=json';
@@ -182,7 +182,7 @@ function gcal_import_geocode_osm($location) {
 
     // https://www.php.net/manual/en/function.json-decode.php
     $decoded = json_decode($json, true);
-    // TODO error handling 
+    // TODO error handling e.g. if we get no usable values. 
 /*
     $file = dirname (__FILE__) . '/json-decoded.txt';
     // should simply be ->lat and -> lon 
@@ -191,9 +191,7 @@ function gcal_import_geocode_osm($location) {
 */
     $lat = $decoded['0']['lat'];
     $lon = $decoded['0']['lon'];
-/*
-    error_log ("gcal_import_geocode_osm found lat=$lat lon=$lon loc $location");
-*/
+    gcal_error_log ("gcal_import_geocode_osm found lat=$lat lon=$lon loc $location");
     return array ($lat, $lon);
 }
 
@@ -216,9 +214,9 @@ function gcal_import_geocode_inofficial($location) {
         } elseif (429 == $http_code) {
             time.sleep(2);  
             ++$attempts; 
-            error_log ("got $attempts HTTP 429 Too Many Requests on $url");
+            gcal_error_log ("INFO: got $attempts HTTP 429 Too Many Requests on $url");
         } else {
-            error_log ("Ärgerlicher HTTP Fehler $http_code");
+            gcal_error_log ("WARN: Unspecified HTTP error $http_code");
             return array ('', '');
         }
     }
diff --git a/gcal-import-worker.php b/gcal-import-worker.php
index d71221b..2a26535 100644
--- a/gcal-import-worker.php
+++ b/gcal-import-worker.php
@@ -34,7 +34,7 @@ function gcal_import_worker() {
     foreach($terms as $term){
         $unique_id = 'gcal_feed_' . $term->name;
         if ( empty ( $options[$unique_id] ) || $options[$unique_id] == '' ) {
-            error_log ( "INFO: link for event category $term->name is not known; next");
+            gcal_error_log ( "INFO: link for event category $term->name is not known; next");
             continue;
         }
 
@@ -66,7 +66,7 @@ The update and delete logic goes as follows:
         }
     	// now we process the current feed. 
         $link = $options[$unique_id];
-        error_log ("INFO: now importing event cat $term->name, link $link");
+        gcal_error_log ("INFO: now importing event cat $term->name, link $link");
     	gcal_import_do_import($term->name, $link);
 
         // look if there are any published event posts in the current event category which were not posted anew or updated (ie recent == false)
@@ -90,7 +90,7 @@ The update and delete logic goes as follows:
             foreach( $post_ids as $post_id ) {
                 $id = $post_id->ID;
                 wp_trash_post( $id );
-                error_log ("Event post $id gelöscht.");
+                gcal_error_log ("Event post $id gelöscht.");
             }  
         }
 
@@ -131,7 +131,7 @@ function gcal_import_do_import($category, $link) {
         if ($r['DTEND'] < $now) {
             continue;
         } else {
-            error_log ("INFO: processing $summary on $dtstart");
+            gcal_error_log ("INFO: processing $summary on $dtstart");
         }
 
         // The zeitstempel. No idea what it's for, but kal3000 seems to use it. 
@@ -193,7 +193,7 @@ function gcal_import_do_import($category, $link) {
             // create image attachment and associate with new post
             $attach = $r['ATTACH'];
             $summary = $r['SUMMARY'];
-            error_log ("INFO: found attachment $attach for $summary");
+            gcal_error_log ("INFO: found attachment $attach for $summary");
         }
 
         if ( isset ( $r['CLASS'] ) && 'PRIVATE' == $r['CLASS']) {
@@ -263,7 +263,7 @@ function gcal_import_do_import($category, $link) {
                 $post_id = wp_insert_post( $post );
                 if ( is_wp_error( $post_id ) ) {    
                     $message = $post_id->get_error_message();
-                    error_log ( "WARN: $message" ); 
+                    gcal_error_log ( "WARN: $message" ); 
                 } else {
                     update_post_meta( $post_id, '_edit_last', $user_id );
                     $now = time();
@@ -271,7 +271,7 @@ function gcal_import_do_import($category, $link) {
                     update_post_meta( $post_id, '_edit_lock', $lock );
                     // and assign the taxonomy type and event category. 
                     wp_set_object_terms( $post_id, $category, 'termine_type' );
-                    error_log ("INFO: posted new post $post_id");
+                    gcal_error_log ("INFO: posted new post $post_id");
                 }
             } else {
                 // good, the post exists already. 
@@ -285,19 +285,19 @@ function gcal_import_do_import($category, $link) {
                     $post_id = wp_update_post( $post, false );
                     // and update the _created field
                     update_post_meta ( $id, '_gcal_created', $lastmodified ); 
-                    error_log ("INFO: updated post $post_id");
+                    gcal_error_log ("INFO: updated post $post_id");
                 } elseif ( $lastmodified == $created ) { 
                     // it was not modified after we created it, so we only update the recent tag. 
                 } elseif ( $lastmodified < $created ) {
                     // iiiiek! A time reversal or a secret time machine! That should not happen! 
-                    error_log ("WARN: post $id last-modified : created $lastmodified < $created ");
+                    gcal_error_log ("WARN: post $id last-modified : created $lastmodified < $created ");
                 }
                 // and set the event to recent = true no matter what. 
                 update_post_meta ( $id, '_gcal_recent', 'true' ); 
             }
         } else {
             $file = dirname (__FILE__) . '/get_posts-' . $post->post_name . '.txt';
-            error_log ("WARN: hmmm, get_posts() did not return an array. Logging to $file");
+            gcal_error_log ("WARN: hmmm, get_posts() did not return an array. Logging to $file");
             file_put_contents ($file, var_export ($post_ids, TRUE)); 
         }
         // and on the next entry. 
diff --git a/gcal-import.php b/gcal-import.php
index 35ba5c9..9f1ca30 100644
--- a/gcal-import.php
+++ b/gcal-import.php
@@ -129,3 +129,17 @@ function gcal_import_uninstall()
 
 register_uninstall_hook( __FILE__, 'gcal_import_uninstall' );
 
+
+/* 
+ * Debug logging if debugging is activated 
+ * 
+ * @since 0.3.0
+ */
+
+function gcal_error_log($args) {
+    $options = get_option('gcal_options');
+    if ( isset ( gcal_options['gcal_debugging'] ) && '1' == gcal_options['gcal_debugging'] ) { 
+        error_log ( $args );
+    }
+}
+