diff --git a/conf/modules/gps_furuno.xml b/conf/modules/gps_furuno.xml
index d1d128dbf9..46b75ee16a 100644
--- a/conf/modules/gps_furuno.xml
+++ b/conf/modules/gps_furuno.xml
@@ -16,7 +16,7 @@
     <file name="gps.h" dir="subsystems"/>
   </header>
   <init fun="gps_nmea_init()"/>
-  <periodic fun="gps_periodic_check(&gps_nmea.state)" freq="1." autorun="TRUE"/>
+  <periodic fun="gps_nmea_periodic_check()" freq="1." autorun="TRUE"/>
   <event fun="gps_nmea_event()"/>
   <makefile target="ap">
     <configure name="FURUNO_GPS_PORT" default="$(GPS_PORT)" case="upper|lower"/>
diff --git a/conf/modules/gps_mediatek_diy.xml b/conf/modules/gps_mediatek_diy.xml
index 5d6c20b6e0..749928366d 100644
--- a/conf/modules/gps_mediatek_diy.xml
+++ b/conf/modules/gps_mediatek_diy.xml
@@ -16,7 +16,7 @@
     <file name="gps.h" dir="subsystems"/>
   </header>
   <init fun="gps_mtk_init()"/>
-  <periodic fun="gps_periodic_check(&gps_mtk.state)" freq="1." autorun="TRUE"/>
+  <periodic fun="gps_mtk_periodic_check()" freq="1." autorun="TRUE"/>
   <event fun="gps_mtk_event()"/>
   <makefile target="ap">
     <configure name="MTK_GPS_PORT" default="$(GPS_PORT)" case="upper|lower"/>
diff --git a/conf/modules/gps_nmea.xml b/conf/modules/gps_nmea.xml
index 0b65a81ab1..531c55f900 100644
--- a/conf/modules/gps_nmea.xml
+++ b/conf/modules/gps_nmea.xml
@@ -16,7 +16,7 @@
     <file name="gps.h" dir="subsystems"/>
   </header>
   <init fun="gps_nmea_init()"/>
-  <periodic fun="gps_periodic_check(&gps_nmea.state)" freq="1." autorun="TRUE"/>
+  <periodic fun="gps_nmea_periodic_check()" freq="1." autorun="TRUE"/>
   <event fun="gps_nmea_event()"/>
   <makefile target="ap">
     <configure name="NMEA_GPS_PORT" default="$(GPS_PORT)" case="upper|lower"/>
diff --git a/conf/modules/gps_nps.xml b/conf/modules/gps_nps.xml
index eef9e367a5..d41d2d26f4 100644
--- a/conf/modules/gps_nps.xml
+++ b/conf/modules/gps_nps.xml
@@ -12,7 +12,7 @@
     <file name="gps.h" dir="subsystems"/>
   </header>
   <init fun="gps_nps_init()"/>
-  <periodic fun="gps_periodic_check(&gps_nps)" freq="1." autorun="TRUE"/>
+  <periodic fun="gps_nps_periodic_check()" freq="1." autorun="TRUE"/>
   <makefile target="nps">
     <file name="gps.c" dir="subsystems"/>
     <file name="gps_sim_nps.c" dir="subsystems/gps"/>
diff --git a/conf/modules/gps_piksi.xml b/conf/modules/gps_piksi.xml
index 8634ded256..2dd37be648 100644
--- a/conf/modules/gps_piksi.xml
+++ b/conf/modules/gps_piksi.xml
@@ -16,7 +16,7 @@
     <file name="gps.h" dir="subsystems"/>
   </header>
   <init fun="gps_piksi_init()"/>
-  <periodic fun="gps_periodic_check(&gps_piksi)" freq="1." autorun="TRUE"/>
+  <periodic fun="gps_piksi_periodic_check()" freq="1." autorun="TRUE"/>
   <event fun="gps_piksi_event()"/>
   <makefile target="ap">
     <configure name="PIKSI_GPS_PORT" default="$(GPS_PORT)" case="upper|lower"/>
diff --git a/conf/modules/gps_sim.xml b/conf/modules/gps_sim.xml
index 04bf7f7495..edc25b558e 100644
--- a/conf/modules/gps_sim.xml
+++ b/conf/modules/gps_sim.xml
@@ -11,7 +11,7 @@
     <file name="gps.h" dir="subsystems"/>
   </header>
   <init fun="gps_sim_init()"/>
-  <periodic fun="gps_periodic_check(&gps)" freq="1." autorun="TRUE"/>
+  <periodic fun="gps_sim_periodic_check()" freq="1." autorun="TRUE"/>
   <makefile target="sim">
     <file name="gps.c" dir="subsystems"/>
     <file name="gps_sim.c" dir="subsystems/gps"/>
diff --git a/conf/modules/gps_sirf.xml b/conf/modules/gps_sirf.xml
index 2902b7b3d0..0cf53947c0 100644
--- a/conf/modules/gps_sirf.xml
+++ b/conf/modules/gps_sirf.xml
@@ -16,7 +16,7 @@
     <file name="gps.h" dir="subsystems"/>
   </header>
   <init fun="gps_sirf_init()"/>
-  <periodic fun="gps_periodic_check(&gps_sirf.state)" freq="1." autorun="TRUE"/>
+  <periodic fun="gps_sirf_periodic_check()" freq="1." autorun="TRUE"/>
   <event fun="gps_sirf_event()"/>
   <makefile target="ap">
     <configure name="SIRF_GPS_PORT" default="$(GPS_PORT)" case="upper|lower"/>
diff --git a/conf/modules/gps_skytraq.xml b/conf/modules/gps_skytraq.xml
index 0c13944868..118862eb14 100644
--- a/conf/modules/gps_skytraq.xml
+++ b/conf/modules/gps_skytraq.xml
@@ -16,7 +16,7 @@
     <file name="gps.h" dir="subsystems"/>
   </header>
   <init fun="gps_skytraq_init()"/>
-  <periodic fun="gps_periodic_check(&gps_skytraq.state)" freq="1." autorun="TRUE"/>
+  <periodic fun="gps_skytraq_periodic_check()" freq="1." autorun="TRUE"/>
   <event fun="gps_skytraq_event()"/>
   <makefile target="ap">
     <configure name="SKYTRAQ_GPS_PORT" default="$(GPS_PORT)" case="upper|lower"/>
diff --git a/conf/modules/gps_ublox.xml b/conf/modules/gps_ublox.xml
index 52e2402434..8e4b76e9e6 100644
--- a/conf/modules/gps_ublox.xml
+++ b/conf/modules/gps_ublox.xml
@@ -16,7 +16,7 @@
     <file name="gps.h" dir="subsystems"/>
   </header>
   <init fun="gps_ubx_init()"/>
-  <periodic fun="gps_periodic_check(&gps_ubx.state)" freq="1." autorun="TRUE"/>
+  <periodic fun="gps_ubx_periodic_check()" freq="1." autorun="TRUE"/>
   <event fun="gps_ubx_event()"/>
   <makefile target="ap">
     <configure name="UBX_GPS_PORT" default="$(GPS_PORT)" case="upper|lower"/>
diff --git a/conf/modules/gps_udp.xml b/conf/modules/gps_udp.xml
index 6a4866b6a9..bf1e564059 100644
--- a/conf/modules/gps_udp.xml
+++ b/conf/modules/gps_udp.xml
@@ -15,7 +15,7 @@
     <file name="gps.h" dir="subsystems"/>
   </header>
   <init fun="gps_udp_init()"/>
-  <periodic fun="gps_periodic_check(&gps_udp)" freq="1." autorun="TRUE"/>
+  <periodic fun="gps_udp_periodic_check()" freq="1." autorun="TRUE"/>
   <makefile target="ap">
     <configure name="GPS_LED" default="none"/>
 
diff --git a/sw/airborne/subsystems/gps.c b/sw/airborne/subsystems/gps.c
index 05f977f3e4..cb6123d002 100644
--- a/sw/airborne/subsystems/gps.c
+++ b/sw/airborne/subsystems/gps.c
@@ -19,9 +19,22 @@
  * Boston, MA 02111-1307, USA.
  */
 
-/** @file gps.c
- *  @brief Device independent GPS code
+/**
+ * @file gps.c
+ * @brief Device independent GPS code.
+ * This provides some general GPS functions and handles the selection of the
+ * currently active GPS (if multiple ones are used).
  *
+ * Each GPS implementation sends a GPS message via ABI for each new measurement,
+ * which can be received by any other part (either from all or only one specific GPS).
+ *
+ * To make it easy to switch to the currently best (or simply the preferred) GPS at runtime,
+ * the #multi_gps_mode can be set to #GPS_MODE_PRIMARY, #GPS_MODE_SECONDARY or #GPS_MODE_AUTO.
+ * This re-sends the GPS message of the "selected" GPS with #GPS_MULTI_ID as sender id.
+ * In the (default) GPS_MODE_AUTO mode, the GPS with the best fix is selected.
+ *
+ * The global #gps struct is also updated from the "selected" GPS
+ * and used to send the normal GPS telemetry messages.
  */
 
 #include "subsystems/abi.h"
diff --git a/sw/airborne/subsystems/gps/gps_mtk.h b/sw/airborne/subsystems/gps/gps_mtk.h
index 7846ab1e9b..cba70e6dcc 100644
--- a/sw/airborne/subsystems/gps/gps_mtk.h
+++ b/sw/airborne/subsystems/gps/gps_mtk.h
@@ -71,6 +71,8 @@ extern struct GpsMtk gps_mtk;
 extern void gps_mtk_event(void);
 extern void gps_mtk_init(void);
 
+#define gps_mtk_periodic_check() gps_periodic_check(&gps_mtk.state)
+
 #ifdef GPS_CONFIGURE
 extern void gps_configure(void);
 extern void gps_configure_uart(void);
diff --git a/sw/airborne/subsystems/gps/gps_nmea.h b/sw/airborne/subsystems/gps/gps_nmea.h
index 26f634946b..0baeaedd76 100644
--- a/sw/airborne/subsystems/gps/gps_nmea.h
+++ b/sw/airborne/subsystems/gps/gps_nmea.h
@@ -26,7 +26,6 @@
  *
 */
 
-
 #ifndef GPS_NMEA_H
 #define GPS_NMEA_H
 
@@ -41,10 +40,6 @@
 #define PRIMARY_GPS GPS_NMEA
 #endif
 
-extern void gps_nmea_init(void);
-extern void gps_nmea_event(void);
-
-
 struct GpsNmea {
   bool msg_available;       ///< flag set to TRUE if a new msg/sentence is available to be parsed
   bool is_configured;       ///< flag set to TRUE if configuration is finished
@@ -59,6 +54,11 @@ struct GpsNmea {
 
 extern struct GpsNmea gps_nmea;
 
+extern void gps_nmea_init(void);
+extern void gps_nmea_event(void);
+
+#define gps_nmea_periodic_check() gps_periodic_check(&gps_nmea.state)
+
 
 /*
  * This part is used by the autopilot to read data from a uart
diff --git a/sw/airborne/subsystems/gps/gps_piksi.h b/sw/airborne/subsystems/gps/gps_piksi.h
index c0ba2356a1..6b979fd4cc 100644
--- a/sw/airborne/subsystems/gps/gps_piksi.h
+++ b/sw/airborne/subsystems/gps/gps_piksi.h
@@ -41,6 +41,8 @@ extern struct GpsState gps_piksi;
 extern void gps_piksi_event(void);
 extern void gps_piksi_init(void);
 
+#define gps_piksi_periodic_check() gps_periodic_check(&gps_piksi)
+
 /*
  * Reset base station position
  */
diff --git a/sw/airborne/subsystems/gps/gps_sim.h b/sw/airborne/subsystems/gps/gps_sim.h
index 88e955ca47..eb4163a1eb 100644
--- a/sw/airborne/subsystems/gps/gps_sim.h
+++ b/sw/airborne/subsystems/gps/gps_sim.h
@@ -9,7 +9,8 @@
 #endif
 
 extern void gps_sim_publish(void);
-
 extern void gps_sim_init(void);
 
+#define gps_sim_periodic_check() gps_periodic_check(&gps)
+
 #endif /* GPS_SIM_H */
diff --git a/sw/airborne/subsystems/gps/gps_sim_nps.h b/sw/airborne/subsystems/gps/gps_sim_nps.h
index 42c6e3c022..14a9841afa 100644
--- a/sw/airborne/subsystems/gps/gps_sim_nps.h
+++ b/sw/airborne/subsystems/gps/gps_sim_nps.h
@@ -14,4 +14,6 @@ extern void gps_feed_value();
 
 extern void gps_nps_init();
 
+#define gps_nps_periodic_check() gps_periodic_check(&gps_nps)
+
 #endif /* GPS_SIM_NPS_H */
diff --git a/sw/airborne/subsystems/gps/gps_sirf.h b/sw/airborne/subsystems/gps/gps_sirf.h
index 6ddfc71b62..b0ec0cc2ce 100644
--- a/sw/airborne/subsystems/gps/gps_sirf.h
+++ b/sw/airborne/subsystems/gps/gps_sirf.h
@@ -59,4 +59,6 @@ extern struct GpsSirf gps_sirf;
 extern void gps_sirf_init(void);
 extern void gps_sirf_event(void);
 
+#define gps_sirf_periodic_check() gps_periodic_check(&gps_sirf.state)
+
 #endif /* GPS_SIRF_H */
diff --git a/sw/airborne/subsystems/gps/gps_skytraq.h b/sw/airborne/subsystems/gps/gps_skytraq.h
index 006385a344..823d3ae7b1 100644
--- a/sw/airborne/subsystems/gps/gps_skytraq.h
+++ b/sw/airborne/subsystems/gps/gps_skytraq.h
@@ -63,4 +63,6 @@ extern struct GpsSkytraq gps_skytraq;
 extern void gps_skytraq_init(void);
 extern void gps_skytraq_event(void);
 
+#define gps_skytraq_periodic_check() gps_periodic_check(&gps_skytraq.state)
+
 #endif /* GPS_SKYTRAQ_H */
diff --git a/sw/airborne/subsystems/gps/gps_ubx.h b/sw/airborne/subsystems/gps/gps_ubx.h
index ab1cd3b21f..5fe25b4484 100644
--- a/sw/airborne/subsystems/gps/gps_ubx.h
+++ b/sw/airborne/subsystems/gps/gps_ubx.h
@@ -46,6 +46,8 @@
 extern void gps_ubx_init(void);
 extern void gps_ubx_event(void);
 
+#define gps_ubx_periodic_check() gps_periodic_check(&gps_ubx.state)
+
 #define GPS_UBX_NB_CHANNELS 16
 
 #define GPS_UBX_MAX_PAYLOAD 255
diff --git a/sw/airborne/subsystems/gps/gps_udp.h b/sw/airborne/subsystems/gps/gps_udp.h
index 22c9725570..072b09ac47 100644
--- a/sw/airborne/subsystems/gps/gps_udp.h
+++ b/sw/airborne/subsystems/gps/gps_udp.h
@@ -13,4 +13,6 @@ extern struct GpsState gps_udp;
 extern void gps_udp_parse(void);
 extern void gps_udp_init(void);
 
+#define gps_udp_periodic_check() gps_periodic_check(&gps_udp)
+
 #endif /* GPS_UDP_H */