FMV question

[JustinFischer]

I am struggling with the multiplexer metadata file, the SensorRelativeAzimuth and SensorRelativeRoll parameters in particular.  I think they are supposed to both be 0, but am not sure.  The sensor was mounted on a UAS on a gimbal and was pointing straight down (nadir view).  I have already read somewhere that the SensorRelativeElevation should be -90 with a camera pointing straight down.  

Another thing I am not sure about is the UnixTimeStamp.  The UAS autopilot is a PixHawk and seems to store date/time messages relative to when the PixHawk was powered up.  So what I did was determine the Unix Time for when the sensor was powered up and then added each date/time message to this initial start date.  This seemed to give me my incremental time units for all the AHR2 messages (these are the messages are subset from all the other messages the autopilot logs).  Everything seemed to run fine with the above parameters set to 0, but wanted to see if anyone else has had this question.  

Note:  I also had to do the time shift (-27) and things started to line up as they should.

Justin 

[ChrisCatania]

Hi Justin - Thanks for asking your questions and welcome to the GeoNet community! I wanted to let you know that we're moving your question to the https://community.esri.com/community/gis/imagery-and-remote-sensing?sr=search&searchId=473a9dbc-3536...‌ space so our Esri and user subject matter experts can further help answer this and future questions.  So you're aware on how and where to post your questions, here's a few quick tips and reminders:

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• This GeoNet 101 "How to Ask Questions on GeoNet" post is also a helpful guide to asking questions: https://community.esri.com/community/help-and-feedback/blog/2016/08/15/community-news-and-tips-how-t...

[CodyBenkelman]

Justin

It sounds to me like you are doing it correctly.  If in doubt, the User Manual at this link

http://esriurl.com/FMV132Manual  should be clear - or if not, let me know and I'll clarify the user doc. 

The PlatformHeading and SensorRelativeAzimuth get combined to determine the sensor heading.  The same is true for the pitch and roll parameters.  So with PlatformPitch = 0 (meaning "level flight") and SensorRelativeElevation = -90, you're telling the multiplexer that the camera is aimed straight down.  

If you have a dynamic gimbal, you'd need to report metadata about the sensor orientation relative to the aircraft body, but in many drone applications, the sensor look angle is fixed, so users apply a fixed value for SensorRelativeAzimuth, SensorRelativeRoll and SensorRelativeElevation.  The results are only approximate, but if you don't have accurate orientation metadata, an estimate is typically the best that can be done.  

This discussion also applies to a variable focal length lens.  If your camera can be dynamically zoomed, you'll need timestamped focal length or field of view metadata to calculate a proper footprint.  

As noted, it sounds like you have it working properly, but if you run into problems let us know

Cody B