diff --git a/helpers/position.php b/helpers/position.php
index 60162ac..519f8c4 100644
--- a/helpers/position.php
+++ b/helpers/position.php
@@ -17,7 +17,7 @@
  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  */
 
-  require_once(ROOT_DIR . "/helpers/db.php");
+require_once(ROOT_DIR . "/helpers/db.php");
 require_once(ROOT_DIR . "/helpers/track.php");
 require_once(ROOT_DIR . "/helpers/upload.php");
 
@@ -332,7 +332,7 @@ require_once(ROOT_DIR . "/helpers/upload.php");
       $lon2 = deg2rad($target->longitude);
       $latD = $lat2 - $lat1;
       $lonD = $lon2 - $lon1;
-      $bearing = 2 * asin(sqrt(pow(sin($latD / 2), 2) + cos($lat1) * cos($lat2) * pow(sin($lonD / 2), 2)));
+      $bearing = 2 * asin(sqrt((sin($latD / 2) ** 2) + cos($lat1) * cos($lat2) * (sin($lonD / 2) ** 2)));
       return $bearing * 6371000;
     }
 
diff --git a/js/src/position.js b/js/src/position.js
new file mode 100644
index 0000000..96d4064
--- /dev/null
+++ b/js/src/position.js
@@ -0,0 +1,86 @@
+/*
+ * μlogger
+ *
+ * Copyright(C) 2019 Bartek Fabiszewski (www.fabiszewski.net)
+ *
+ * This is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+import uUtils from './utils.js';
+
+/**
+ * @class uPosition
+ * @property {number} id
+ * @property {number} latitude
+ * @property {number} longitude
+ * @property {?number} altitude
+ * @property {?number} speed
+ * @property {?number} bearing
+ * @property {?number} accuracy
+ * @property {?string} provider
+ * @property {?string} comment
+ * @property {?string} image
+ * @property {string} username
+ * @property {string} trackname
+ * @property {number} trackid
+ * @property {number} timestamp
+ * @property {number} distance
+ * @property {number} seconds
+ * @property {number} totalDistance
+ * @property {number} totalSeconds
+ */
+export default class uPosition {
+
+  /**
+   * @throws On invalid input
+   * @param {Object} pos
+   * @returns {uPosition}
+   */
+  static fromJson(pos) {
+    const position = new uPosition();
+    position.id = uUtils.getInteger(pos.id);
+    position.latitude = uUtils.getFloat(pos.latitude);
+    position.longitude = uUtils.getFloat(pos.longitude);
+    position.altitude = uUtils.getInteger(pos.altitude, true); // may be null
+    position.speed = uUtils.getInteger(pos.speed, true); // may be null
+    position.bearing = uUtils.getInteger(pos.bearing, true); // may be null
+    position.accuracy = uUtils.getInteger(pos.accuracy, true); // may be null
+    position.provider = uUtils.getString(pos.provider, true); // may be null
+    position.comment = uUtils.getString(pos.comment, true); // may be null
+    position.image = uUtils.getString(pos.image, true); // may be null
+    position.username = uUtils.getString(pos.username);
+    position.trackname = uUtils.getString(pos.trackname);
+    position.trackid = uUtils.getInteger(pos.trackid);
+    position.timestamp = uUtils.getInteger(pos.timestamp);
+    position.distance = uUtils.getInteger(pos.distance);
+    position.seconds = uUtils.getInteger(pos.seconds);
+    position.totalDistance = 0;
+    position.totalSeconds = 0;
+    return position;
+  }
+
+  /**
+   * @return {boolean}
+   */
+  hasComment() {
+    return (this.comment != null && this.comment.length > 0);
+  }
+
+  /**
+   * @return {boolean}
+   */
+  hasImage() {
+    return (this.image != null && this.image.length > 0);
+  }
+}
diff --git a/js/test/position.test.js b/js/test/position.test.js
new file mode 100644
index 0000000..6678b0b
--- /dev/null
+++ b/js/test/position.test.js
@@ -0,0 +1,214 @@
+/*
+ * μlogger
+ *
+ * Copyright(C) 2019 Bartek Fabiszewski (www.fabiszewski.net)
+ *
+ * This is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+import uPosition from '../src/position.js';
+
+describe('Position tests', () => {
+
+  const nullableProperties = [
+    'altitude',
+    'speed',
+    'bearing',
+    'accuracy',
+    'provider',
+    'comment',
+    'image'
+  ];
+  const nonNullableProperties = [
+    'id',
+    'latitude',
+    'longitude',
+    'timestamp',
+    'username',
+    'trackid',
+    'trackname',
+    'distance',
+    'seconds'
+  ];
+  const properties = nullableProperties.concat(nonNullableProperties);
+
+  let posId;
+  let latitude;
+  let longitude;
+  let altitude;
+  let speed;
+  let bearing;
+  let timestamp;
+  let accuracy;
+  let provider;
+  let comment;
+  let image;
+  let username;
+  let trackid;
+  let trackname;
+  let distance;
+  let seconds;
+
+  let jsonPosition;
+
+  beforeEach(() => {
+    posId = 110286;
+    latitude = 11.221871666666999;
+    longitude = 22.018848333333001;
+    altitude = -39;
+    speed = 0;
+    bearing = null;
+    timestamp = 1564250017;
+    accuracy = 9;
+    provider = 'gps';
+    comment = null;
+    image = '134_5d3c8fa92ebac.jpg';
+    username = 'test';
+    trackid = 134;
+    trackname = 'Test name';
+    distance = 0;
+    seconds = 0;
+
+    jsonPosition = {
+      'id': posId,
+      'latitude': latitude,
+      'longitude': longitude,
+      'altitude': altitude,
+      'speed': speed,
+      'bearing': bearing,
+      'timestamp': timestamp,
+      'accuracy': accuracy,
+      'provider': provider,
+      'comment': comment,
+      'image': image,
+      'username': username,
+      'trackid': trackid,
+      'trackname': trackname,
+      'distance': distance,
+      'seconds': seconds
+    };
+  });
+
+  it('should create uPosition instance from json object', () => {
+    // when
+    const position = uPosition.fromJson(jsonPosition);
+    // then
+    expect(position.id).toBe(posId);
+    expect(position.latitude).toBe(latitude);
+    expect(position.longitude).toBe(longitude);
+    expect(position.speed).toBe(speed);
+    expect(position.bearing).toBe(bearing);
+    expect(position.timestamp).toBe(timestamp);
+    expect(position.accuracy).toBe(accuracy);
+    expect(position.provider).toBe(provider);
+    expect(position.comment).toBe(comment);
+    expect(position.image).toBe(image);
+    expect(position.username).toBe(username);
+    expect(position.trackid).toBe(trackid);
+    expect(position.trackname).toBe(trackname);
+    expect(position.distance).toBe(distance);
+    expect(position.seconds).toBe(seconds);
+  });
+
+  describe('should raise error on undefined property', () => {
+    properties.forEach((prop) => {
+      it(`testing property: ${prop}`, () => {
+        // given
+        const posCopy = { ...jsonPosition };
+        // when
+        delete posCopy[prop];
+        // then
+        expect(() => { uPosition.fromJson(posCopy); }).toThrow(new Error('Illegal value'));
+      });
+    });
+  });
+
+  describe('should raise error on null non-nullable property', () => {
+    nonNullableProperties.forEach((prop) => {
+      it(`testing property: ${prop}`, () => {
+        // given
+        const posCopy = { ...jsonPosition };
+        // when
+        posCopy[prop] = null;
+        // then
+        expect(() => { uPosition.fromJson(posCopy); }).toThrow(new Error('Illegal value'));
+      });
+    });
+  });
+
+  describe('should not raise error on null nullable property', () => {
+    nullableProperties.forEach((prop) => {
+      it(`testing property: ${prop}`, () => {
+        // given
+        const posCopy = { ...jsonPosition };
+        // when
+        posCopy[prop] = null;
+        let pos = {};
+        // then
+        expect(() => { pos = uPosition.fromJson(posCopy); }).not.toThrow(new Error('Illegal value'));
+        expect(pos[prop]).toBeNull();
+      });
+    });
+  });
+
+  it('should result false on null comment', () => {
+    // when
+    jsonPosition.comment = null;
+    const position = uPosition.fromJson(jsonPosition);
+    // then
+    expect(position.hasComment()).toBe(false);
+  });
+
+  it('should result false on empty comment', () => {
+    // when
+    jsonPosition.comment = '';
+    const position = uPosition.fromJson(jsonPosition);
+    // then
+    expect(position.hasComment()).toBe(false);
+  });
+
+  it('should result true on non-null comment', () => {
+    // when
+    jsonPosition.comment = 'comment';
+    const position = uPosition.fromJson(jsonPosition);
+    // then
+    expect(position.hasComment()).toBe(true);
+  });
+
+
+  it('should result false on null image', () => {
+    // when
+    jsonPosition.image = null;
+    const position = uPosition.fromJson(jsonPosition);
+    // then
+    expect(position.hasImage()).toBe(false);
+  });
+
+  it('should result false on empty image', () => {
+    // when
+    jsonPosition.image = '';
+    const position = uPosition.fromJson(jsonPosition);
+    // then
+    expect(position.hasImage()).toBe(false);
+  });
+
+  it('should result true on non-null image', () => {
+    // when
+    jsonPosition.image = 'image';
+    const position = uPosition.fromJson(jsonPosition);
+    // then
+    expect(position.hasImage()).toBe(true);
+  });
+
+});
diff --git a/utils/getpositions.php b/utils/getpositions.php
index 5bbf9f2..5f827ad 100644
--- a/utils/getpositions.php
+++ b/utils/getpositions.php
@@ -49,42 +49,35 @@ if ($userId) {
   }
 }
 
-header("Content-type: text/xml");
-$xml = new XMLWriter();
-$xml->openURI("php://output");
-$xml->startDocument("1.0");
-$xml->setIndent(true);
-$xml->startElement('root');
-
-if (!empty($positionsArr)) {
+$result = [];
+if ($positionsArr === false) {
+  $result = [ "error" => true ];
+} else if (!empty($positionsArr)) {
   foreach ($positionsArr as $position) {
-    /** @var uPosition $prevPosition */
-    $xml->startElement("position");
-    $xml->writeAttribute("id", $position->id);
-      $xml->writeElement("latitude", $position->latitude);
-      $xml->writeElement("longitude", $position->longitude);
-      $xml->writeElement("altitude", ($position->altitude) ? round($position->altitude) : $position->altitude);
-      $xml->writeElement("speed", $position->speed);
-      $xml->writeElement("bearing", $position->bearing);
-      $xml->writeElement("timestamp", $position->timestamp);
-      $xml->writeElement("accuracy", $position->accuracy);
-      $xml->writeElement("provider", $position->provider);
-      $xml->writeElement("comment", $position->comment);
-      $xml->writeElement("image", $position->image);
-      $xml->writeElement("username", $position->userLogin);
-      $xml->writeElement("trackid", $position->trackId);
-      $xml->writeElement("trackname", $position->trackName);
-      $distance = !$last && isset($prevPosition) ? $position->distanceTo($prevPosition) : 0;
-      $xml->writeElement("distance", round($distance));
-      $seconds = !$last && isset($prevPosition) ? $position->secondsTo($prevPosition) : 0;
-      $xml->writeElement("seconds", $seconds);
-    $xml->endElement();
+    $distance = !$last && isset($prevPosition) ? $position->distanceTo($prevPosition) : 0;
+    $seconds = !$last && isset($prevPosition) ? $position->secondsTo($prevPosition) : 0;
+    $result[] = [
+      "id" => $position->id,
+      "latitude" => $position->latitude,
+      "longitude" => $position->longitude,
+      "altitude" => ($position->altitude) ? round($position->altitude) : $position->altitude,
+      "speed" => $position->speed,
+      "bearing" => $position->bearing,
+      "timestamp" => $position->timestamp,
+      "accuracy" => $position->accuracy,
+      "provider" => $position->provider,
+      "comment" => $position->comment,
+      "image" => $position->image,
+      "username" => $position->userLogin,
+      "trackid" => $position->trackId,
+      "trackname" => $position->trackName,
+      "distance" => round($distance),
+      "seconds" => $seconds
+    ];
     $prevPosition = $position;
   }
 }
-
-$xml->endElement();
-$xml->endDocument();
-$xml->flush();
+header("Content-type: application/json");
+echo json_encode($result);
 
 ?>