CGO3+ image EXIF data "below sea level"?

[Satdiver]

Hello all,

I've recently conducted a small mapping mission for a client that included 48 .JPEG images. Shortly after processing the images, I realized that I couldn't open the digital elevation model (DEM). I opened the EXIF data from one of the images and noticed that the GPS Reference Altitude is listed as "Below Sea Level" when the flight altitude is 31 meters. I believe this may be the reason my DEM won't open.

I did a forum search and didn't find much of an answer to this issue. I know I can change this individually in each image with an EXIF editor but really don't want to have to do this if there is a controller setting fix to this issue from happening in the future. I reached out to Yuneec USA Support and speaking to them by live chat on their website, asked if this could be changed in the controller or camera so that it doesn't happen on future flights. Their recommendation was to update the camera firmware. Well, I'm already using the latest firmware, v3.2.34(A) and don't think this is the answer.

So, does anyone here know how/if this can be resolved by a means other than individual EXIF edits? I appreciate you're assistance in advance.

Thanks

Todd

 

[PatR]

I don’t know how to correct it but obtaining a below sea level altitude is quite easy to obtain. If flying at a low enough altitude in low enough temperature and low humidity the baro pressure can easily be below sea level pressure. Well below sea level. Pressure barometers initially sense “sea level” using a “standard day”, which exists at a pressure of 29.92HG, 59*F, and zero humidity. Higher pressure with a lower temp will generate <sea level.

 

[Satdiver]

I don’t know how to correct it but obtaining a below sea level altitude is quite easy to obtain. If flying at a low enough altitude in low enough temperature and low humidity the baro pressure can easily be below sea level pressure. Well below sea level. Pressure barometers initially sense “sea level” using a “standard day”, which exists at a pressure of 29.92HG, 59*F, and zero humidity. Higher pressure with a lower temp will generate <sea level.

Thanks PatR. I also found that the GPS location data was assigned a minus ("-") sign. Do you know if this minus sign is assigned as long as the pressure barometer is sensing "below sea level?" I assume it would be a positive number if the barometer was sensing "above sea level."

This flight was at approximately 1045 am on a day that was really close to the conditions you mention. Thanks again.

 

[PatR]

I don't believe GPS position data is what is used to establish altitude with Yuneec's equipment. Best guess is the pressure sensor provides height data reference.

 

[Steve Carr]

In addition, the alt reading is reset to zero each time the motors are started. Sometimes I restart the motors several times to get a stable reading. I seem to recall that the sd card needs to be formatted as Fat32 and not exFAT.

 

[CrashALot]

was this in death valley, it is -282 ft ?