Ouster fix to use host timestamp and imu gravity inverted

os1_fix.patch

diff --git a/ouster_ros/src/os1_cloud_node.cpp b/ouster_ros/src/os1_cloud_node.cpp
index 8a7e8ec..964cfa6 100644
--- a/ouster_ros/src/os1_cloud_node.cpp
+++ b/ouster_ros/src/os1_cloud_node.cpp
@@ -59,6 +59,7 @@ int main(int argc, char** argv) {
         [&](uint64_t scan_ts) mutable {
             msg = ouster_ros::OS1::cloud_to_cloud_msg(
                 cloud, std::chrono::nanoseconds{scan_ts}, lidar_frame);
+	    msg.header.stamp = ros::Time::now();
             lidar_pub.publish(msg);
         });
 
@@ -67,7 +68,9 @@ int main(int argc, char** argv) {
     };
 
     auto imu_handler = [&](const PacketMsg& p) {
-        imu_pub.publish(ouster_ros::OS1::packet_to_imu_msg(p, imu_frame));
+        sensor_msgs::Imu msg = ouster_ros::OS1::packet_to_imu_msg(p, imu_frame);
+        msg.header.stamp = ros::Time::now();
+        imu_pub.publish(msg);
     };
 
     auto lidar_packet_sub = nh.subscribe<PacketMsg, const PacketMsg&>(
diff --git a/ouster_ros/src/os1_ros.cpp b/ouster_ros/src/os1_ros.cpp
index abb437c..d6d7a08 100644
--- a/ouster_ros/src/os1_ros.cpp
+++ b/ouster_ros/src/os1_ros.cpp
@@ -26,7 +26,7 @@ bool read_lidar_packet(const client& cli, PacketMsg& m) {
 
 sensor_msgs::Imu packet_to_imu_msg(const PacketMsg& p,
                                    const std::string& frame) {
-    const double standard_g = 9.80665;
+    const double standard_g = -9.80665;
     sensor_msgs::Imu m;
     const uint8_t* buf = p.buf.data();