launch: count multi UAVs from 0

This fixes the IDs of multi UAVs started with ROS/Gazebo.

Previously the 3 vehicles were displayed in QGC as Vehicle 2, 3, 4.
With this change it is more intuitive Vehicle 1, 2, 3 and this is
also consistent with the way it is documented and how it is in
jMAVSim.

launch/multi_uav_mavros_sitl.launch

@@ -19,11 +19,11 @@
         <arg name="verbose" value="$(arg verbose)"/>
         <arg name="paused" value="$(arg paused)"/>
     </include>
-    <!-- UAV1 -->
-    <group ns="uav1">
+    <!-- UAV0 -->
+    <group ns="uav0">
         <!-- MAVROS and vehicle configs -->
-        <arg name="ID" value="1"/>
-        <arg name="fcu_url" default="udp://:14541@localhost:14581"/>
+        <arg name="ID" value="0"/>
+        <arg name="fcu_url" default="udp://:14540@localhost:14580"/>
         <!-- PX4 SITL and vehicle spawn -->
         <include file="$(find px4)/launch/single_vehicle_spawn.launch">
             <arg name="x" value="0"/>
@@ -33,23 +33,23 @@
             <arg name="P" value="0"/>
             <arg name="Y" value="0"/>
             <arg name="vehicle" value="$(arg vehicle)"/>
-            <arg name="mavlink_udp_port" value="14561"/>
-            <arg name="mavlink_tcp_port" value="4561"/>
+            <arg name="mavlink_udp_port" value="14560"/>
+            <arg name="mavlink_tcp_port" value="4560"/>
             <arg name="ID" value="$(arg ID)"/>
         </include>
         <!-- MAVROS -->
         <include file="$(find mavros)/launch/px4.launch">
             <arg name="fcu_url" value="$(arg fcu_url)"/>
             <arg name="gcs_url" value=""/>
-            <arg name="tgt_system" value="$(eval 1 + arg('ID'))"/>
+            <arg name="tgt_system" value="$(eval 0 + arg('ID'))"/>
             <arg name="tgt_component" value="1"/>
         </include>
     </group>
-    <!-- UAV2 -->
-    <group ns="uav2">
+    <!-- UAV1 -->
+    <group ns="uav1">
         <!-- MAVROS and vehicle configs -->
-        <arg name="ID" value="2"/>
-        <arg name="fcu_url" default="udp://:14542@localhost:14582"/>
+        <arg name="ID" value="1"/>
+        <arg name="fcu_url" default="udp://:14541@localhost:14581"/>
         <!-- PX4 SITL and vehicle spawn -->
         <include file="$(find px4)/launch/single_vehicle_spawn.launch">
             <arg name="x" value="1"/>
@@ -59,8 +59,8 @@
             <arg name="P" value="0"/>
             <arg name="Y" value="0"/>
             <arg name="vehicle" value="$(arg vehicle)"/>
-            <arg name="mavlink_udp_port" value="14562"/>
-            <arg name="mavlink_tcp_port" value="4562"/>
+            <arg name="mavlink_udp_port" value="14561"/>
+            <arg name="mavlink_tcp_port" value="4561"/>
             <arg name="ID" value="$(arg ID)"/>
         </include>
         <!-- MAVROS -->
@@ -71,12 +71,11 @@
             <arg name="tgt_component" value="1"/>
         </include>
     </group>
-
-    <!-- UAV3 -->
-    <group ns="uav3">
+    <!-- UAV2 -->
+    <group ns="uav2">
         <!-- MAVROS and vehicle configs -->
-        <arg name="ID" value="3"/>
-        <arg name="fcu_url" default="udp://:14543@localhost:14583"/>
+        <arg name="ID" value="2"/>
+        <arg name="fcu_url" default="udp://:14542@localhost:14582"/>
         <!-- PX4 SITL and vehicle spawn -->
         <include file="$(find px4)/launch/single_vehicle_spawn.launch">
             <arg name="x" value="0"/>
@@ -86,8 +85,8 @@
             <arg name="P" value="0"/>
             <arg name="Y" value="0"/>
             <arg name="vehicle" value="$(arg vehicle)"/>
-            <arg name="mavlink_udp_port" value="14563"/>
-            <arg name="mavlink_tcp_port" value="4563"/>
+            <arg name="mavlink_udp_port" value="14562"/>
+            <arg name="mavlink_tcp_port" value="4562"/>
             <arg name="ID" value="$(arg ID)"/>
         </include>
         <!-- MAVROS -->