# Mavlink LOCAL\_POSITION\_NED not publishing **URL:** \ **Category:** ArduSub\ **Created:** [November 8, 2023, 11:54pm UTC](https://discuss.bluerobotics.com/t/mavlink-local-position-ned-not-publishing/15458 "2023-11-08T23:54:33Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![jayparikh](https://avatars.discourse-cdn.com/v4/letter/j/8edcca/32.png) [@jayparikh](https://discuss.bluerobotics.com/u/jayparikh)\ **Post date:** [November 8, 2023, 11:54pm UTC](https://discuss.bluerobotics.com/t/mavlink-local-position-ned-not-publishing/15458/1 "2023-11-08T23:54:33Z")
Hello, I’m trying to read local position data from ArduSub for autonomy but it’s not publishing. I’m using cube orange, jetson nano and communicating using serial telem1 port. I do see the message GPS: No GPS fix, does the Ardusub require GPS fix for publishing data? Thank you for helping! Jay Parikh ---
**Author:** ![tony-white](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.bluerobotics.com/tony-white/32/13297_2.png) [@tony-white](https://discuss.bluerobotics.com/u/tony-white)\ **Post date:** [November 9, 2023, 12:52am UTC](https://discuss.bluerobotics.com/t/mavlink-local-position-ned-not-publishing/15458/2 "2023-11-09T00:52:15Z")
Hi Jay! Unfortunately, GPS signals do not penetrate water! You can fit your vehicle with a GPS that will work if the antenna is exposed to the sky, but otherwise you need another means of locating the vehicle. This is usually done with acoustics - via either a [DVL](https://bluerobotics.com/store/the-reef/dvl-a50/), [USBL](https://ceruleansonar.com/products/rov-locator-mark-iii), or [Underwater GPS](https://waterlinked.com/shop/underwater-gps-g2-bluerov2-kit-131?category=15). Checkout our guide to [sonar tech](https://bluerobotics.com/learn/a-smooth-operators-guide-to-underwater-sonars-and-acoustic-devices/#positioning-and-navigation-sonar) for more info! ---
**Author:** ![jayparikh](https://avatars.discourse-cdn.com/v4/letter/j/8edcca/32.png) [@jayparikh](https://discuss.bluerobotics.com/u/jayparikh)\ **Post date:** [November 9, 2023, 3:37pm UTC](https://discuss.bluerobotics.com/t/mavlink-local-position-ned-not-publishing/15458/3 "2023-11-09T15:37:11Z")
Hi Anthony, Is there any way I can get position estimate using IMU/ Gyro data? ---
**Author:** ![tony-white](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.bluerobotics.com/tony-white/32/13297_2.png) [@tony-white](https://discuss.bluerobotics.com/u/tony-white)\ **Post date:** [November 9, 2023, 5:18pm UTC](https://discuss.bluerobotics.com/t/mavlink-local-position-ned-not-publishing/15458/4 "2023-11-09T17:18:18Z")
Hi Jay - You could develop your own code to integrate the filtered output from the IMU, but I wouldn’t expect it to perform very well. This is a common question on our forums: > [@ROV and AUV Localization an Introduction](https://discuss.bluerobotics.com/t/rov-and-auv-localization-an-introduction/519): > > Hey Blue Robotics Community! Relatively frequently I see people asking about, hovering, dead reckoning, and using GPS or IMUs for localization. This is often enough I think perhaps it would be useful to have a small guide on localizing underwater vehicles. This a first draft and should be considered an introductory guide. Any comments, criticisms, or things that I left off are welcomed and appreciated. Why is localization a problem for underwater vehicles? In the field of in air robotics, lo… > [@IMU Double Integration Python Code](https://discuss.bluerobotics.com/t/imu-double-integration-python-code/11295): > > Hey guys, We are currently trying to automate the BlueROV2 to scan our university pool. We need underwater GPS to correct for the positioning. Although we know that double integrating the IMU may lead to highly inaccurate results, we want to try it initially. Is there a Python code that is ready to use for this? I have been searching for days and am unable to find one. Thanks! > [@ArduSub: Using IMU for horizontal positioning](https://discuss.bluerobotics.com/t/ardusub-using-imu-for-horizontal-positioning/399/2): > > Hi Magnus, You can get the rough position from inertial data only. Keep in mind that it will drift quite a bit. @jaxxzer has spent some time testing this and has some videos on Youtube of the BlueROV reacting to position changes with only inertial sensing. I’ll point him towards this post. -Rusty > [@Position calculation based on IMU data](https://discuss.bluerobotics.com/t/position-calculation-based-on-imu-data/4760/7): > > @mseskar, I will point out that what you are trying to do will probably not work well. The imu data from the autopilot board is not suitable (precise) for dead reckoning. Here is some more information: > [@Pymavlink SET\_POSITION\_TARGET with velocity](https://discuss.bluerobotics.com/t/pymavlink-set-position-target-with-velocity/12839/10): > > Just a quick note on top of Eliot’s precious comments. You can do positioning with only IMUs generally but the IMUs you need to be looking for are starting at least 20 times of a Pixhawk in price and much bigger in size. So in theory possible but with the current ArduSub ecosystem not. Resources are vastly available to search for it. Such techniques usually require hardware that is an order of magnitude more expensive and precise. Cheaper and easier to use acoustic based solutions! ---
**Author:** ![jayparikh](https://avatars.discourse-cdn.com/v4/letter/j/8edcca/32.png) [@jayparikh](https://discuss.bluerobotics.com/u/jayparikh)\ **Post date:** [November 9, 2023, 8:11pm UTC](https://discuss.bluerobotics.com/t/mavlink-local-position-ned-not-publishing/15458/5 "2023-11-09T20:11:07Z")
Thank you Anthony!