diff --git a/worldwind-gs-layergroup-getmapcallback/README.md b/worldwind-gs-layergroup-getmapcallback/README.md
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@@ -0,0 +1,9 @@
+<img src="https://worldwind.arc.nasa.gov/css/images/nasa-logo.svg" height="100"/> 
+
+# WorldWind Server Kit (WWSK)
+## WorldWind LayerGroup GetMapCallback (worldwind-gs-layergroup-getmapcallback)
+
+This module implements a GetMapCallback that culls layers from GetMap requests 
+that are outside the request's bbox.
+
+* It resolves an "null bbox" IllegalArgumentException issue 
diff --git a/worldwind-gs-layergroup-getmapcallback/pom.xml b/worldwind-gs-layergroup-getmapcallback/pom.xml
new file mode 100644
index 00000000..15e900c9
--- /dev/null
+++ b/worldwind-gs-layergroup-getmapcallback/pom.xml
@@ -0,0 +1,216 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>gov.nasa.worldwind.server</groupId>
+        <artifactId>worldwind-serverkit</artifactId>
+        <version>0.6.0-SNAPSHOT</version>
+    </parent>
+    <artifactId>worldwind-gs-layergroup-getmapcallback</artifactId>
+    <packaging>jar</packaging>
+
+    <!--=====================================================================-->
+    <!--Project Information                                                  -->
+    <!--=====================================================================-->    
+    <name>WorldWind LayerGroupGetMapCallback</name>
+    <description>A GetMapCallback that improves performance and rendering of LayerGroups</description>
+    <url>https://github.com/NASAWorldWind/WorldWindServerKit</url>
+    <organization>
+        <name>NASA World Wind</name>
+        <url>https://worldwind.arc.nasa.gov</url>
+    </organization>
+    <licenses>
+        <license>
+            <name>General Public License (GPL)</name>
+            <url>http://www.gnu.org/copyleft/gpl.txt</url>
+        </license>
+    </licenses>
+    <developers />
+    <contributors />
+    <mailingLists />
+    <prerequisites />    
+    
+    <!--=====================================================================-->
+    <!--Environment Settings                                                 -->
+    <!--=====================================================================-->    
+    <scm>
+        <url>https://github.com/NASAWorldWind/WorldWindServerKit</url>
+        <connection>scm:git:git://github.com/NASAWorldWind/WorldWindServerKit.git</connection>
+        <developerConnection>scm:git:https://github.com/NASAWorldWind/WorldWindServerKit.git</developerConnection>
+        <tag>HEAD</tag>
+    </scm>    
+    <issueManagement>
+        <system>GitHub Issues</system>
+        <url>https://github.com/NASAWorldWind/WorldWindServerKit/issues</url>
+    </issueManagement>
+    <ciManagement>
+        <system>Travis CI</system>
+        <url>https://travis-ci.org/NASAWorldWind/WorldWindServerKit</url>
+    </ciManagement>
+    <distributionManagement />    
+    
+    <!--=====================================================================-->
+    <!--The Basics                                                           -->
+    <!--=====================================================================-->
+    <dependencies>
+        <!--Dependencies common the GeoServer modules-->
+        <dependency>
+            <groupId>org.geotools</groupId>
+            <artifactId>gt-api</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.geotools</groupId>
+            <artifactId>gt-main</artifactId>
+        </dependency>        
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-beans</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-core</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-context</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-webmvc</artifactId>
+        </dependency>        
+        
+        <!--GeoServer Web Map Service module-->
+        <dependency>
+            <groupId>org.geoserver</groupId>
+            <artifactId>gs-wms</artifactId>
+        </dependency>
+
+
+        <!--Test dependencies-->
+        <dependency>
+            <groupId>org.geoserver</groupId>
+            <artifactId>gs-platform</artifactId>
+            <classifier>tests</classifier>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.geoserver</groupId>
+            <artifactId>gs-main</artifactId>
+            <classifier>tests</classifier>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.geoserver</groupId>
+            <artifactId>gs-wms</artifactId>
+            <classifier>tests</classifier>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.geoserver</groupId>
+            <artifactId>gs-wfs</artifactId>
+            <classifier>tests</classifier>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.geoserver.extension</groupId>
+            <artifactId>gs-wps-core</artifactId>
+            <scope>test</scope>
+            <classifier>tests</classifier>
+        </dependency>
+        <dependency>
+            <groupId>org.geoserver.web</groupId>
+            <artifactId>gs-web-core</artifactId>
+            <classifier>tests</classifier>
+            <scope>test</scope>
+        </dependency>    
+        <dependency>
+            <groupId>org.geoserver.web</groupId>
+            <artifactId>gs-web-demo</artifactId>
+            <scope>test</scope>
+        </dependency>   
+        <dependency>
+            <groupId>org.geotools</groupId>
+            <artifactId>gt-sample-data</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.easymock</groupId>
+            <artifactId>easymockclassextension</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>javax.servlet</groupId>
+            <artifactId>javax.servlet-api</artifactId>
+            <version>3.0.1</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <!--=====================================================================-->
+    <!--Build Settings                                                       -->
+    <!--=====================================================================-->
+    <build>
+        <plugins />
+        <resources>
+            <resource>
+                <directory>${basedir}/src/main/java</directory>
+                <includes>
+                    <!--Spring bean factory configuration-->
+                    <include>applicationContext.xml</include>
+                </includes>
+            </resource>
+        </resources>
+        <testResources>
+            <testResource>
+                <directory>src/test/resources</directory>
+            </testResource>     
+        </testResources>    
+    </build>    
+    <reporting /> 
+    <profiles>
+        <!--Generate the javadocs and sources jar files when the "release" profile is activated-->
+        <profile>
+            <id>release</id>
+            <activation>
+                <property>
+                    <name>release</name>
+                </property>
+            </activation>
+            <dependencies />
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-javadoc-plugin</artifactId>
+                        <executions>
+                            <execution>
+                                <id>attach-javadocs</id>
+                                <goals>
+                                    <goal>jar</goal>
+                                </goals>
+                            </execution>
+                        </executions>            
+                    </plugin>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-source-plugin</artifactId>
+                        <executions>
+                            <execution>
+                                <id>attach-sources</id>
+                                <goals>
+                                    <goal>jar</goal>
+                                </goals>
+                            </execution>
+                        </executions>            
+                    </plugin>               
+                </plugins>
+            </build>
+            <modules />
+        </profile>
+    </profiles>
+</project>
diff --git a/worldwind-gs-layergroup-getmapcallback/src/main/java/applicationContext.xml b/worldwind-gs-layergroup-getmapcallback/src/main/java/applicationContext.xml
new file mode 100644
index 00000000..27e1c008
--- /dev/null
+++ b/worldwind-gs-layergroup-getmapcallback/src/main/java/applicationContext.xml
@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- 
+Copyright (C) 2014 - 2016 Open Source Geospatial Foundation. All rights reserved.
+This code is licensed under the GPL 2.0 license, available at the root
+application directory.
+-->
+<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
+
+<beans>
+    
+                                                                        
+    <bean id="simplifingGetMapCallback" class="gov.nasa.worldwind.gs.wms.SimplifyingGetMapCallback"/>
+    
+                    
+</beans>
diff --git a/worldwind-gs-layergroup-getmapcallback/src/main/java/gov/nasa/worldwind/gs/wms/SimplifyingGetMapCallback.java b/worldwind-gs-layergroup-getmapcallback/src/main/java/gov/nasa/worldwind/gs/wms/SimplifyingGetMapCallback.java
new file mode 100644
index 00000000..1f066d6f
--- /dev/null
+++ b/worldwind-gs-layergroup-getmapcallback/src/main/java/gov/nasa/worldwind/gs/wms/SimplifyingGetMapCallback.java
@@ -0,0 +1,231 @@
+/*
+ * Copyright (C) 2017 NASA WorldWind
+ */
+
+package gov.nasa.worldwind.gs.wms;
+
+import com.vividsolutions.jts.geom.Envelope;
+import it.geosolutions.jaiext.interpolators.InterpolationBicubic;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import javax.media.jai.Interpolation;
+import org.geoserver.ows.Dispatcher;
+import org.geoserver.ows.KvpRequestReader;
+import org.geoserver.wms.*;
+import org.geotools.geometry.jts.ReferencedEnvelope;
+import org.geotools.map.Layer;
+import org.geotools.referencing.CRS;
+import org.geotools.renderer.lite.RendererUtilities;
+import org.geotools.styling.FeatureTypeStyle;
+import org.geotools.styling.Rule;
+import org.geotools.styling.Style;
+import org.geotools.util.logging.Logging;
+import org.opengis.referencing.FactoryException;
+import org.opengis.referencing.crs.CoordinateReferenceSystem;
+import org.opengis.referencing.operation.TransformException;
+
+/**
+ * This GetMapCallback is responsible for simplifying a complex a map request.
+ */
+public class SimplifyingGetMapCallback implements GetMapCallback {
+
+    static final Logger logger = Logging.getLogger("org.geoserver.wms");
+
+    public SimplifyingGetMapCallback() {
+    }
+
+    /**
+     * Marks the beginning of a GetMap request internal processing
+     *
+     * @param request Request to be examined and modified
+     * @return Modified request
+     */
+    @Override
+    public GetMapRequest initRequest(GetMapRequest request) {
+        logger.log(Level.INFO, " ** GetMapCallback.initRequest: {0}", request.toString());
+
+        //
+        // Culling logic
+        //
+        List<MapLayerInfo> layers = request.getLayers();
+        List<Style> styles = request.getStyles();
+        List<MapLayerInfo> filteredLayers = new ArrayList<>();
+        List<Style> filteredStyles = new ArrayList<>();
+               
+        ReferencedEnvelope requestBounds;
+        double requestMapScaleDenominator;
+        
+        
+        logger.info("Starting Culling Logic");
+        try {
+            final String srs4326 = WMS.toInternalSRS("EPSG:4326", WMS.version(request.getVersion()));
+            CoordinateReferenceSystem crs4326 = CRS.decode("EPSG:4326");
+
+            CoordinateReferenceSystem crs = request.getCrs();
+            Envelope bbox = request.getBbox();
+            if (request.getSRS().equals(srs4326)) {
+                if (request.getVersion().equals("1.3.0")) {
+                    // NOTE: In WMS 1.3.0, the specification of "EPSG:4326" has the axis swapped
+                    requestBounds = new ReferencedEnvelope(bbox.getMinY(), bbox.getMaxY(), bbox.getMinX(), bbox.getMaxX(), crs4326);
+                } else {
+                    requestBounds = new ReferencedEnvelope(bbox, crs4326);
+                }
+            } else {
+                // Transform to EPSG:4326
+                requestBounds = new ReferencedEnvelope(bbox, crs).transform(crs4326, true);
+            }
+            // Compute the map scale to be used in rules
+            requestMapScaleDenominator = RendererUtilities.calculateScale(requestBounds,
+                    request.getWidth(), request.getHeight(), null);
+
+        } catch (FactoryException | TransformException ex) {
+            Logger.getLogger(SimplifyingGetMapCallback.class.getName()).log(Level.SEVERE, null, ex);
+            return request;
+        }
+
+        logger.log(Level.INFO, "------------- Layers size: {0}", layers.size());
+
+        logger.info("------- Layers within bounds and scale extents:");
+        for (int i = 0; i < layers.size(); i++) {
+            MapLayerInfo currentLayer = layers.get(i);
+            try {
+                // Only include layers that intersect the request bounds
+                if (currentLayer.getLatLongBoundingBox().intersects((Envelope) requestBounds)) {
+
+                    // Only include layers are not excluded by a min/max scale rule
+                    boolean excluded = false;
+                    Style currentStyle = styles.get(i);
+
+                    for (FeatureTypeStyle featureTypeStyle : currentStyle.featureTypeStyles()) {
+                        for (Rule rule : featureTypeStyle.rules()) {
+                            // If not defined in a rule, the getMinScaleDenominator defaults to zero
+                            // and the getMaxScaleDenominator defaults to max double
+                            if (rule.getMaxScaleDenominator() <= requestMapScaleDenominator
+                                    || rule.getMinScaleDenominator() > requestMapScaleDenominator) {
+                                excluded = true;
+                                break;
+                            }
+                        }
+                    }
+                    if (!excluded) {
+                        logger.log(Level.INFO, "******** {0}", currentLayer.getName());
+                        filteredLayers.add(currentLayer);
+                        filteredStyles.add(currentStyle);
+                    }
+                }
+
+            } catch (IOException ex) {
+                logger.log(Level.SEVERE, null, ex);
+            }
+        }
+
+        // Clear hidden layers from the list (assumes a sorted layer list)
+        // Starting from the highest resolution, traverse the list until
+        // we have a layer that occludes all others before it.
+        for (int i = filteredLayers.size() - 1; i > -1; i--) {
+            MapLayerInfo layer = filteredLayers.get(i);
+            try {
+                // If a layer is completely completely covers the request bounds,
+                // remove the layers before it except n layers immediately preceeding it.
+                if (layer.getLatLongBoundingBox().covers(requestBounds)) {
+                    int n = 1; // num preceeding layers to keep
+                    int last = Math.max(0, i - n);
+                    // This does actually clear the elements from the list
+                    // Operations on a sublist effect the original list
+                    filteredLayers.subList(0, last).clear();
+                    filteredStyles.subList(0, last).clear();
+                    break;
+                }
+
+            } catch (IOException ex) {
+                System.out.println(ex.getMessage());
+                logger.log(Level.SEVERE, null, ex);
+            }
+        }
+        
+        // Replace the request layers with the filtered layers and corresponding styles
+        if (filteredLayers.size() > 0) {
+            logger.log(Level.INFO, "============= filteredLayers size: {0}", filteredLayers.size());
+            request.setLayers(filteredLayers);
+            request.setStyles(filteredStyles);
+        }
+
+        logger.info("Finished Culling logic");
+        return request;
+    }
+
+    /**
+     * Called when the WMSMapContent is created (at this point the WMSMapContent
+     * is empty) On multidimensional requests against multi-frame output formats
+     * (e.g. animated GIF) this method can be called multiple times, once per
+     * generated frame
+     *
+     * @param content
+     */
+    @Override
+    public void initMapContent(WMSMapContent content) {
+        // nothing to do
+        // TODO: can store info in meta data if needed
+        // e.g.: content.getMetadata().put(... , ...)
+        logger.log(Level.FINE, " ** GetMapCallback.initMapContent: {0}", content.toString());
+    }
+
+    /**
+     * Called before a layer gets added to the map content, allows the layer to
+     * be modified. If the returned value is null the layer will not be added to
+     * the map content
+     *
+     * @param content
+     * @param layer
+     * @return
+     */
+    @Override
+    public Layer beforeLayer(WMSMapContent content, Layer layer) {
+        logger.log(Level.INFO, " ** GetMapCallback.beforeLayer: {0},{1}", new Object[]{layer.getTitle(), layer.getStyle().getName()});
+        return layer;
+    }
+
+    /**
+     * Inspects and eventually manipulates the WMSMapContent, returning a
+     * WMSMapContent that will be used for map rendering. In case of multi-frame
+     * output formats this method will be called once per frame.
+     *
+     * @param mapContent
+     * @return
+     */
+    @Override
+    public WMSMapContent beforeRender(WMSMapContent mapContent) {
+        logger.log(Level.FINE, " ** GetMapCallback.beforeRender: {0}", mapContent.toString());
+        return mapContent;
+    }
+
+    /**
+     * Called once when the rendering is completed, allows the output WebMap to
+     * be inspected, modified or replaced altogether
+     *
+     * @param map
+     * @return
+     */
+    @Override
+    public WebMap finished(WebMap map) {
+        logger.log(Level.FINE, " ** GetMapCallback.finished: {0}", map.toString());
+        return map;
+    }
+
+    /**
+     * Called if the GetMap fails for any reason.
+     *
+     * @param t
+     */
+    @Override
+    public void failed(Throwable t) {
+        logger.log(Level.FINE, " ** GetMapCallback.failed! {0}", t.toString());
+        // nothing to do
+    }
+
+}
\ No newline at end of file