diff --git a/lucene/spatial/src/java/org/apache/lucene/spatial/prefix/tree/SpatialPrefixTreeFactory.java b/lucene/spatial/src/java/org/apache/lucene/spatial/prefix/tree/SpatialPrefixTreeFactory.java
index bbb01df0d22..f5a4bc49426 100644
--- a/lucene/spatial/src/java/org/apache/lucene/spatial/prefix/tree/SpatialPrefixTreeFactory.java
+++ b/lucene/spatial/src/java/org/apache/lucene/spatial/prefix/tree/SpatialPrefixTreeFactory.java
@@ -31,6 +31,9 @@ import java.util.Map;
 public abstract class SpatialPrefixTreeFactory {
 
   private static final double DEFAULT_GEO_MAX_DETAIL_KM = 0.001;//1m
+  public static final String PREFIX_TREE = "prefixTree";
+  public static final String MAX_LEVELS = "maxLevels";
+  public static final String MAX_DIST_ERR = "maxDistErr";
 
   protected Map<String, String> args;
   protected SpatialContext ctx;
@@ -42,7 +45,7 @@ public abstract class SpatialPrefixTreeFactory {
    */
   public static SpatialPrefixTree makeSPT(Map<String,String> args, ClassLoader classLoader, SpatialContext ctx) {
     SpatialPrefixTreeFactory instance;
-    String cname = args.get("prefixTree");
+    String cname = args.get(PREFIX_TREE);
     if (cname == null)
       cname = ctx.isGeo() ? "geohash" : "quad";
     if ("geohash".equalsIgnoreCase(cname))
@@ -68,14 +71,14 @@ public abstract class SpatialPrefixTreeFactory {
   }
 
   protected void initMaxLevels() {
-    String mlStr = args.get("maxLevels");
+    String mlStr = args.get(MAX_LEVELS);
     if (mlStr != null) {
       maxLevels = Integer.valueOf(mlStr);
       return;
     }
 
     double degrees;
-    String maxDetailDistStr = args.get("maxDetailDist");
+    String maxDetailDistStr = args.get(MAX_DIST_ERR);
     if (maxDetailDistStr == null) {
       if (!ctx.isGeo()) {
         return;//let default to max
@@ -83,9 +86,6 @@ public abstract class SpatialPrefixTreeFactory {
       degrees = DistanceUtils.dist2Degrees(DEFAULT_GEO_MAX_DETAIL_KM, DistanceUtils.EARTH_MEAN_RADIUS_KM);
     } else {
       degrees = Double.parseDouble(maxDetailDistStr);
-      if (ctx.isGeo()) {
-        degrees = DistanceUtils.dist2Degrees(Double.parseDouble(maxDetailDistStr), DistanceUtils.EARTH_MEAN_RADIUS_KM);
-      }
     }
     maxLevels = getLevelForDistance(degrees);
   }
diff --git a/solr/core/src/java/org/apache/solr/schema/AbstractSpatialFieldType.java b/solr/core/src/java/org/apache/solr/schema/AbstractSpatialFieldType.java
index 90c9b943736..7ed8640910e 100644
--- a/solr/core/src/java/org/apache/solr/schema/AbstractSpatialFieldType.java
+++ b/solr/core/src/java/org/apache/solr/schema/AbstractSpatialFieldType.java
@@ -62,6 +62,11 @@ public abstract class AbstractSpatialFieldType<T extends SpatialStrategy> extend
   protected void init(IndexSchema schema, Map<String, String> args) {
     super.init(schema, args);
 
+    String units = args.remove("units");
+    if (!"degrees".equals(units))
+      throw new SolrException(SolrException.ErrorCode.SERVER_ERROR,
+          "Must specify units=\"degrees\" on field types with class "+getClass().getSimpleName());
+
     //Solr expects us to remove the parameters we've used.
     MapListener<String, String> argsWrap = new MapListener<String, String>(args);
     ctx = SpatialContextFactory.makeSpatialContext(argsWrap, schema.getResourceLoader().getClassLoader());
diff --git a/solr/core/src/test-files/solr/collection1/conf/schema-spatial.xml b/solr/core/src/test-files/solr/collection1/conf/schema-spatial.xml
index e094c7238f4..266873b6004 100644
--- a/solr/core/src/test-files/solr/collection1/conf/schema-spatial.xml
+++ b/solr/core/src/test-files/solr/collection1/conf/schema-spatial.xml
@@ -27,22 +27,22 @@
     <fieldType name="string" class="solr.StrField" sortMissingLast="true"/>
 
     <fieldType name="srpt_geohash"   class="solr.SpatialRecursivePrefixTreeFieldType"
-               prefixTree="geohash"
+               prefixTree="geohash" units="degrees"
         />
     <fieldType name="srpt_quad"   class="solr.SpatialRecursivePrefixTreeFieldType"
-              prefixTree="quad"
+              prefixTree="quad" units="degrees"
         />
     <fieldType name="srpt_100km"   class="solr.SpatialRecursivePrefixTreeFieldType"
-              maxDetailDist="0.9"
+              maxDistErr="0.9" units="degrees"
         />
     <fieldType name="stqpt_geohash"   class="solr.SpatialTermQueryPrefixTreeFieldType"
-              prefixTree="geohash" />
+              prefixTree="geohash" units="degrees" />
 
     <fieldType name="stqpt_u"  class="solr.SpatialTermQueryPrefixTreeFieldType"
-        geo="false" distCalculator="cartesian^2" worldBounds="0 0 1000 1000"/>
+        geo="false" distCalculator="cartesian^2" worldBounds="0 0 1000 1000" units="degrees"/>
 
     <fieldType name="twodoubles" class="solr.SpatialTwoDoublesFieldType"
-               numberType="tdouble"/>
+               numberType="tdouble" units="degrees"/>
 
   </types>
 
diff --git a/solr/example/solr/collection1/conf/schema.xml b/solr/example/solr/collection1/conf/schema.xml
index b34f9969075..caaf5036dce 100755
--- a/solr/example/solr/collection1/conf/schema.xml
+++ b/solr/example/solr/collection1/conf/schema.xml
@@ -686,7 +686,7 @@
       http://wiki.apache.org/solr/SolrAdaptersForLuceneSpatial4
     -->
     <fieldType name="location_rpt" class="solr.SpatialRecursivePrefixTreeFieldType"
-        geo="true" distErrPct="0.025" maxDetailDist="0.000009" />
+        geo="true" distErrPct="0.025" maxDistErr="0.000009" units="degrees" />
 
    <!-- Money/currency field type. See http://wiki.apache.org/solr/MoneyFieldType
         Parameters: