diff --git a/gnss/2.1/default/GnssMeasurement.h b/gnss/2.1/default/GnssMeasurement.h
new file mode 100644
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+++ b/gnss/2.1/default/GnssMeasurement.h
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+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <android/hardware/gnss/2.1/IGnssMeasurement.h>
+#include <hidl/MQDescriptor.h>
+#include <hidl/Status.h>
+#include <atomic>
+#include <mutex>
+#include <thread>
+
+namespace android {
+namespace hardware {
+namespace gnss {
+namespace V2_1 {
+namespace implementation {
+
+using GnssDataV2_1 = V2_1::IGnssMeasurementCallback::GnssData;
+
+using ::android::sp;
+using ::android::hardware::hidl_array;
+using ::android::hardware::hidl_memory;
+using ::android::hardware::hidl_string;
+using ::android::hardware::hidl_vec;
+using ::android::hardware::Return;
+using ::android::hardware::Void;
+
+struct GnssMeasurement : public IGnssMeasurement {
+    GnssMeasurement();
+    ~GnssMeasurement();
+    // Methods from V1_0::IGnssMeasurement follow.
+    Return<V1_0::IGnssMeasurement::GnssMeasurementStatus> setCallback(
+            const sp<V1_0::IGnssMeasurementCallback>& callback) override;
+    Return<void> close() override;
+
+    // Methods from V1_1::IGnssMeasurement follow.
+    Return<V1_0::IGnssMeasurement::GnssMeasurementStatus> setCallback_1_1(
+            const sp<V1_1::IGnssMeasurementCallback>& callback, bool enableFullTracking) override;
+
+    // Methods from V2_0::IGnssMeasurement follow.
+    Return<V1_0::IGnssMeasurement::GnssMeasurementStatus> setCallback_2_0(
+            const sp<V2_0::IGnssMeasurementCallback>& callback, bool enableFullTracking) override;
+
+    // Methods from V2_1::IGnssMeasurement follow.
+    Return<V1_0::IGnssMeasurement::GnssMeasurementStatus> setCallback_2_1(
+            const sp<V2_1::IGnssMeasurementCallback>& callback, bool enableFullTracking) override;
+
+  private:
+    void start();
+    void stop();
+    void reportMeasurement(const GnssDataV2_1&);
+
+    static sp<IGnssMeasurementCallback> sCallback;
+    std::atomic<long> mMinIntervalMillis;
+    std::atomic<bool> mIsActive;
+    std::thread mThread;
+    mutable std::mutex mMutex;
+};
+
+}  // namespace implementation
+}  // namespace V2_1
+}  // namespace gnss
+}  // namespace hardware
+}  // namespace android