diff --git a/cdm/src/main/java/ucar/nc2/NetcdfFile.java b/cdm/src/main/java/ucar/nc2/NetcdfFile.java
index 6bb581e..d5650f7 100644
--- a/cdm/src/main/java/ucar/nc2/NetcdfFile.java
+++ b/cdm/src/main/java/ucar/nc2/NetcdfFile.java
@@ -998,6 +998,19 @@ public class NetcdfFile implements ucar.nc2.util.cache.FileCacheable {
   }
 
   /**
+   * Return true if this file supports querying for locality information.
+   * @return if the file can return locality information
+   * @throws IOException if there is not an IOServiceProvider set
+   */
+  public boolean supportsLocalityInformation() throws IOException {
+    if (spi == null) {
+      throw new IOException("spi is null");
+    }
+
+    return spi.supportsLocalityInformation();
+  }
+
+  /**
    * Return the unlimited (record) dimension, or null if not exist.
    * If there are multiple unlimited dimensions, it will return the first one.
    * @return the unlimited Dimension, or null if none.
@@ -1737,6 +1750,15 @@ public class NetcdfFile implements ucar.nc2.util.cache.FileCacheable {
     sbuff.append( escapeName(v.getShortName()));
   }
 
+  public Array getLocalityInformation(ucar.nc2.Variable v, Section ranges) throws IOException, InvalidRangeException {
+    if (spi == null) {
+      throw new IOException("spi is null");
+    } else if (!spi.supportsLocalityInformation()) { 
+      throw new IOException("IOSP " + spi.getFileTypeId() + " does not support getLocalityInformation()");
+    }
+
+    return spi.getLocalityInformation(v, ranges);
+  }
 
   //////////////////////////////////////////////////////////////////////////////////////
   // Service Provider calls
diff --git a/cdm/src/main/java/ucar/nc2/Variable.java b/cdm/src/main/java/ucar/nc2/Variable.java
index 172e447..963e9b8 100644
--- a/cdm/src/main/java/ucar/nc2/Variable.java
+++ b/cdm/src/main/java/ucar/nc2/Variable.java
@@ -592,6 +592,36 @@ public class Variable implements VariableIF, ProxyReader {
   }
 
   /**
+   * Return an ArrayLong structure with the same shape as the shape arguement
+   * where each entry is the offset in the byte-stream where the corresponding
+   * data element begins
+   * @param origin int array specifying the starting index. If null, assume all zeroes.
+   * @param shape  int array specifying the extents in each dimension.
+   *               This becomes the shape of the returned Array.
+   * @return a memory-resdient array of longs with offsets or -1 if the offset
+   *                for the corresponding cell can't be determined
+   */
+  public Array getLocalityInformation(int[] origin, int[] shape) throws IOException, InvalidRangeException {
+    return ncfile.getLocalityInformation( this, new Section(origin, shape));
+  }
+
+  /**
+   * Return an ArrayLong structure with the same shape as the shape arguement
+   * where each entry is the offset in the byte-stream where the corresponding
+   * data element begins.
+   *
+   * @param section list of Range specifying the section of data to read.
+   *                Must be null or same rank as variable.
+   *                If list is null, assume all data.
+   *                Each Range corresponds to a Dimension. If the Range object is null, it means use the entire dimension.
+   * @return a memory-resdient array of longs with offsets or -1 if the offset
+   *                for the corresponding cell can't be determined
+   */
+  public Array getLocalityInformation(Section section) throws IOException, InvalidRangeException {
+    return ncfile.getLocalityInformation(this, section);
+  }
+
+  /**
    * Read data section specified by a "section selector", and return a memory resident Array. Uses
    * Fortran 90 array section syntax.
    *
diff --git a/cdm/src/main/java/ucar/nc2/iosp/AbstractIOServiceProvider.java b/cdm/src/main/java/ucar/nc2/iosp/AbstractIOServiceProvider.java
index 27aa316..9d61d95 100644
--- a/cdm/src/main/java/ucar/nc2/iosp/AbstractIOServiceProvider.java
+++ b/cdm/src/main/java/ucar/nc2/iosp/AbstractIOServiceProvider.java
@@ -105,6 +105,16 @@ public abstract class AbstractIOServiceProvider implements IOServiceProvider {
   }
 
   @Override
+  public boolean supportsLocalityInformation() throws IOException {
+    throw new IOException("This IOSP does not support getLocalityInformation()");
+  }
+
+  @Override
+  public Array getLocalityInformation(ucar.nc2.Variable v2, Section section) throws IOException, InvalidRangeException {
+    throw new IOException("This IOSP does not support getLocalityInformation()");
+  }
+
+  @Override
   public StructureDataIterator getStructureIterator(Structure s, int bufferSize) throws java.io.IOException {
     return null;
   }
diff --git a/cdm/src/main/java/ucar/nc2/iosp/IOServiceProvider.java b/cdm/src/main/java/ucar/nc2/iosp/IOServiceProvider.java
index e4f4e85..61d070f 100644
--- a/cdm/src/main/java/ucar/nc2/iosp/IOServiceProvider.java
+++ b/cdm/src/main/java/ucar/nc2/iosp/IOServiceProvider.java
@@ -124,6 +124,32 @@ public interface IOServiceProvider {
    */
   public ucar.ma2.Array readSection(ParsedSectionSpec cer) throws IOException, InvalidRangeException;
 
+  /**
+   * Calculate the offset in the underlying byte-stream for each value
+   * indicated by the section and variable objects
+   *
+   * @param v2 a top-level Variable
+   * @param section the section of data to read.
+   *   There must be a Range for each Dimension in the variable, in order.
+   *   Note: no nulls allowed. IOSP may not modify.
+   * @return an ArrayLong the same shape as section where each entry is the 
+   *         offset of the corresponding data element
+   * @throws java.io.IOException if read error or if this IOSP doesn't 
+   *                             support getLocalityInformation()
+   * @throws ucar.ma2.InvalidRangeException if invalid section
+   */
+  public ucar.ma2.Array getLocalityInformation(ucar.nc2.Variable v2, Section section) 
+         throws IOException, InvalidRangeException;
+
+  /**
+   * Determine if this IOServiceProvider supports the getLocalityInformation() function
+   *
+   * @return a boolean indicating if getLocalityInformation is supported by
+   *         this IOServiceProvider
+   */
+  public boolean supportsLocalityInformation() throws IOException;
+
+
   // iosps with top level sequences must override
   public StructureDataIterator getStructureIterator(Structure s, int bufferSize) throws java.io.IOException;