diff --git a/src/backend/data/schema.js b/src/backend/data/schema.js
index 7003c46f..6efc7ff1 100644
--- a/src/backend/data/schema.js
+++ b/src/backend/data/schema.js
@@ -456,6 +456,14 @@ const GraphQLListContainer = new GraphQLObjectType({
   interfaces: [nodeInterface]
 })
 
+const GeoPoint = new GraphQLInputObjectType({
+  name: 'GeoPoint',
+  fields: {
+    lat: {type: GraphQLFloat},
+    lon: {type: GraphQLFloat},
+  }
+})
+
 const GraphQLUser = new GraphQLObjectType({
   name: 'User',
   description: 'User of ground control',
@@ -554,10 +562,13 @@ const GraphQLUser = new GraphQLObjectType({
     intervieweeForCallAssignment: {
       type: GraphQLPerson,
       args: {
-        callAssignmentId: {type: GraphQLString}
+        callAssignmentId: {type: GraphQLString},
+        center: {type: GeoPoint},
+        radiusMeters: {type: GraphQLFloat}
       },
-      resolve: async(user, {callAssignmentId}, {rootValue}) => {
-
+      resolve: async(
+        user, {callAssignmentId, center, radiusMeters}, {rootValue}
+      ) => {
         let localCallAssignmentId = fromGlobalId(callAssignmentId)
         if (localCallAssignmentId.type !== 'CallAssignment')
           localCallAssignmentId = callAssignmentId
@@ -647,6 +658,21 @@ const GraphQLUser = new GraphQLObjectType({
         if (userAddress)
           query = query.whereNot('bsd_people.cons_id', userAddress.cons_id)
 
+        // Filter by distance from a geographical point.
+        // Spatial ref 4326 is WGS 84, in degrees
+        // Spatial ref 900913 is Google Web Mercator, in meters
+        if (center && radiusMeters > 0) {
+          query = query.whereRaw(`
+            ST_DWithin(bsd_addresses.geom,
+              ST_Transform(
+                ST_SetSRID(ST_MakePoint(${center.lon}, ${center.lat}), 4326),
+                900913
+              ),
+              ${radiusMeters}
+            )
+          `)
+        }
+
         log.info(`Running query: ${query}`)
 
         let person    = await query
diff --git a/src/frontend/components/CallAssignment.js b/src/frontend/components/CallAssignment.js
index 3ebc24a9..f7f3407c 100644
--- a/src/frontend/components/CallAssignment.js
+++ b/src/frontend/components/CallAssignment.js
@@ -12,6 +12,7 @@ import SubmitCallSurvey from '../mutations/SubmitCallSurvey'
 import CallStatsBar from './CallStatsBar'
 import MutationHandler from './MutationHandler'
 import {PhoneNumberFormat, PhoneNumberUtil} from 'google-libphonenumber'
+import getDefaultRelayParams from '../helpers/getDefaultRelayParams'
 const phoneUtil = PhoneNumberUtil.getInstance()
 
 const SurveyRenderers = {
@@ -408,8 +409,24 @@ ${userFirstName}`
   }
 }
 
+// Convert the hash parameters 'query[lat]', 'query[lon]', and 'query[miles]'
+// into the API arguments for the center and radius of the filter region.
+const hashParams = getDefaultRelayParams({
+  lat: null,  // latitude in degrees north
+  lon: null,  // longitude in degrees east
+  miles: null  // radius in miles
+})
+const center = (isFinite(hashParams.lat) && isFinite(hashParams.lon)) ?
+  {lat: hashParams.lat, lon: hashParams.lon} : null
+const radiusMeters = isFinite(hashParams.miles) ?
+  hashParams.miles * 1609.34 : null
+
 export default Relay.createContainer(CallAssignment, {
-  initialVariables: { id: '' },
+  initialVariables: {
+    id: '',
+    center: center,
+    radiusMeters: radiusMeters
+  },
   fragments: {
     callAssignment: () => Relay.QL`
       fragment on CallAssignment {
@@ -428,9 +445,11 @@ export default Relay.createContainer(CallAssignment, {
       fragment on User {
         id
         firstName
-        allCallsMade:callsMade(forAssignmentId:$id)
-        completedCallsMade:callsMade(forAssignmentId:$id,completed:true)
-        intervieweeForCallAssignment(callAssignmentId:$id) {
+        allCallsMade: callsMade(forAssignmentId: $id)
+        completedCallsMade: callsMade(forAssignmentId: $id, completed: true)
+        intervieweeForCallAssignment(
+          callAssignmentId: $id, center: $center, radiusMeters: $radiusMeters
+        ) {
           id
           prefix
           firstName