P4P altitude incorrect with GS Pro

[sarflyer]

hey guys,
I recently started using DJI GS Pro on P4P for mapping.

I did a mission at 100 ft and when I checked exif data, the altitude is off by + 65 feet !!

firmware and everything is current..

Any advice ?

thanks in advance

 

[Fly Dawg]

From the few I have looked at the Exif data never matches the app or flight log data. It's generally off anywhere from 10-15 feet. Not much you can do about it.

 

[sar104]

hey guys,
I recently started using DJI GS Pro on P4P for mapping.

I did a mission at 100 ft and when I checked exif data, the altitude is off by + 65 feet !!

firmware and everything is current..

Any advice ?

thanks in advance

Which EXIF data did you look at? The altitude data commonly presented in software is the GPS altitude above MSL, which has two sources of error - GPS vertical error and reference ellipsoid deviation from the MSL geoid.

However, the EXIF data do contain the barometrically-derived altitude relative to the takeoff point too - you just have to look more closely. For example, extracted from a JPEG:

GPS Altitude Ref : Above Sea Level
GPS Altitude : 3233 m Above Sea Level
Absolute Altitude : +3233.03
Relative Altitude : +248.10

 

[ersylvia]

I'm having the same issue. I have an elevation of ~50ft MSL. I created a planned route to fly 200ft AGL using DJI GS Pro with my P4P. My Phantom took off, headed to the start point, and proceeded to increase in altitude. My drone was nearly twice as high as the set elevation when I started to bring it down.

Did a test box in an open field, rather than over a stream, set the flight altitude around 60ft and started. My Phantom, again, just kept rising until I paused and brought it down, but it reached an altitude of ~150ft until I did so.

I did not check the EXIF data.... I just know how high it the drone should've gone.

Definitely looking for some answers on this issue also. Thanks.

 

[sarflyer]

Which EXIF data did you look at? The altitude data commonly presented in software is the GPS altitude above MSL, which has two sources of error - GPS vertical error and reference ellipsoid deviation from the MSL geoid.

However, the EXIF data do contain the barometrically-derived altitude relative to the takeoff point too - you just have to look more closely. For example, extracted from a JPEG:

GPS Altitude Ref : Above Sea Level
GPS Altitude : 3233 m Above Sea Level
Absolute Altitude : +3233.03
Relative Altitude : +248.10

I'm looking at Exif data from Jpeg details tab. see attached.

it was flown at 100 ft, seems the height it flew was about right.

my theory is that P4P Exif is recording at MSL ( btw- that MSL doesn't look accurate compared to local sea elevation )

anyone know if I can set the exif report to be AGL ?

 

[sar104]

I'm looking at Exif data from Jpeg details tab. see attached.

it was flown at 100 ft, seems the height it flew was about right.

my theory is that P4P Exif is recording at MSL ( btw- that MSL doesn't look accurate compared to local sea elevation )

anyone know if I can set the exif report to be AGL ?

I'm not sure what you mean by "set exif the report to be AGL". The DJI EXIF data contain both GPS MSL data and barometric altitude relative to take off point. Those data are in meters by the way, not feet. If a particular program is only extracting and displaying one of those then you would need to see if that program has other options. Are you referring to EXIF data reported by GS Pro?

 

[sarflyer]

I'm not sure what you mean by "set exif the report to be AGL". The DJI EXIF data contain both GPS MSL data and barometric altitude relative to take off point. Those data are in meters by the way, not feet. If a particular program is only extracting and displaying one of those then you would need to see if that program has other options. Are you referring to EXIF data reported by GS Pro?

pardon my lack of knowledge as I'm new to this stuff.
Exif I refer to is from the Jpeg, and I can only see One altitude info.
attached is what I see.

you mentioned that "The DJI EXIF data contain both GPS MSL data and barometric altitude ".

where can you see them both ?

 

[OneTenthOfaMileHighClub]

Hi SarFlyer,

You may be either very pleased, pr perhaps slightly depressed by an expanded exposure to some of the other [EXIF] data stored with each click of the sDJI shutter [P4P in this example]'
You can download the excellent ExifTool program which is available for download at

ExifTool by Phil Harvey

Attached is an image, and the ExitTool extracted data. It was taken with the drone at about 75 meters above take-off point, which in turn, is perhaps about (3-4 meters Sea level).

Exif data is extracted below.

You will notice TWO areas of info pertaining to Altitude, with the "Relative Altitude" giving the 'Above take-off' height [75.3m]. GPS Altitude
Just below it is the "Absolute Altitude" [37.371m], which in this case is absolute rubbish, if you are expecting any reference to Sea-Level. (79m would be more correct)

It is interesting to note that a Windows Program called 'Advanced Renamer' allows the batch renaming of images based on many of the available fields, so for instance you could rename a image with date, GPS Location, etc.

Try it on some of your images, and look at the numbers. I am sure it will help'

Best Wishes

p.s. Place the Exif Tool on the desktop, and rename it "exiftool(-a -u -g1 -w txt).exe" (no quotes, spacing exactly as is). Then Drag and drop a file on top of it, and a text file will be credted with all the Exif Data as below.

==============================================
EXIF Data Follows
==============================================
---- ExifTool ----
ExifTool Version Number : 10.68
Warning : [minor] Possibly incorrect maker notes offsets (fix by 1783?)
---- System ----
File Name : 2018-01-17 PortMacq 286_[31.3 m Above Sea Level],(+75.30m Rel).JPG
Directory : P:/2018-Q1/2018-01-17 DJI PortMacq ForSale
File Size : 8.6 MB
File Modification Date/Time : 2018:01:17 15:28:15+11:00
File Access Date/Time : 2018:01:17 15:10:03+11:00
File Creation Date/Time : 2018:01:17 15:10:03+11:00
File Permissions : rw-rw-rw-
---- File ----
File Type : JPEG
File Type Extension : jpg
MIME Type : image/jpeg
Exif Byte Order : Little-endian (Intel, II)
Image Width : 5472
Image Height : 3648
Encoding Process : Baseline DCT, Huffman coding
Bits Per Sample : 8
Color Components : 3
Y Cb Cr Sub Sampling : YCbCr4:2:2 (2 1)
---- IFD0 ----
Image Description : DCIM\100MEDIA\DJI_0286.JPG
Make : DJI
Camera Model Name : FC6310
Orientation : Horizontal (normal)
X Resolution : 72
Y Resolution : 72
Resolution Unit : inches
Software : v01.05.1577
Modify Date : 2018:01:17 15:28:14
Y Cb Cr Positioning : Centered
XP Comment : Type=N, Mode=P, DE=None
XP Keywords : v01.05.1577;1.1.6;v1.0.0
---- ExifIFD ----
Exposure Time : 1/200
F Number : 4.5
Exposure Program : Program AE
ISO : 100
Exif Version : 0230
Date/Time Original : 2018:01:17 15:28:14
Create Date : 2018:01:17 15:28:14
Components Configuration : -, Cr, Cb, Y
Compressed Bits Per Pixel : 3.492772616
Shutter Speed Value : 1/200
Aperture Value : 4.5
Exposure Compensation : 0
Max Aperture Value : 2.8
Subject Distance : 0 m
Metering Mode : Center-weighted average
Light Source : Unknown
Flash : No flash function
Focal Length : 8.8 mm
Flashpix Version : 0010
Color Space : sRGB
Exif Image Width : 5472
Exif Image Height : 3648
Exposure Index : undef
File Source : Digital Camera
Scene Type : Directly photographed
Custom Rendered : Normal
Exposure Mode : Auto
White Balance : Auto
Digital Zoom Ratio : undef
Focal Length In 35mm Format : 24 mm
Scene Capture Type : Standard
Gain Control : None
Contrast : Normal
Saturation : Normal
Sharpness : Normal
Subject Distance Range : Unknown
Serial Number : d3ae
---- DJI ----
Make : DJI
DJI 0x0002 : 1 2 0 0
Speed X : +0.10
Speed Y : +0.10
Speed Z : +0.00
Pitch : +9.10
Yaw : +53.50
Roll : +9.00
Camera Pitch : -17.70
Camera Yaw : +51.30
Camera Roll : +0.00
DJI 0x000c : 1.50463402461595e-036 9.29110734889936e-035
DJI 0x000d : 2684354560 262151 808452096 2684432433
DJI 0x000e : 0
DJI 0x000f : 0
DJI 0x0010 : 38
DJI 0x0011 : 0
DJI 0x0012 : 0
DJI 0x0013 : 65539 65536 -1610481664 65540 358612992
DJI 0x0014 : 2684551168 65540 239075328
DJI 0x0017 : 1
DJI 0x0019 : 64
DJI 0x001a : 13
DJI 0x001b : 0
DJI 0x001c : 124
DJI 0x001d : 123
DJI 0x001e : 12.09375
DJI 0x001f : 0
DJI 0x0020 : 0
DJI 0x0021 : 0
DJI 0x0022 : 0
DJI 0x0023 : 0
DJI 0x0024 : 0 0 5 160 4 0 1 0 0 0 144 2 0 0 21 162 5 0 1 0 0 0 247 [...]
---- InteropIFD ----
Interoperability Index : R98 - DCF basic file (sRGB)
Interoperability Version : 0100
---- GPS ----
GPS Version ID : 2.3.0.0
GPS Latitude Ref : South
GPS Latitude : 31 deg 25' 55.75"
GPS Longitude Ref : East
GPS Longitude : 152 deg 54' 7.84"
GPS Altitude Ref : Above Sea Level
GPS Altitude : 31.371 m <<<<<<
---- IFD1 ----
Compression : JPEG (old-style)
X Resolution : 72
Y Resolution : 72
Resolution Unit : inches
Thumbnail Offset : 3072
Thumbnail Length : 10759
Thumbnail Image : (Binary data 10759 bytes, use -b option to extract)
---- XMP-rdf ----
About : DJI Meta Data
---- XMP-xmp ----
Modify Date : 2018:01:17
Create Date : 2018:01:17
---- XMP-tiff ----
Make : DJI
Camera Model Name : FC6310
---- XMP-dc ----
Format : image/jpg
---- XMP-drone-dji ----
Absolute Altitude : +31.37 <<<<<<<<<
Relative Altitude : +75.30 <<<<<<<<<
Gimbal Roll Degree : +0.00
Gimbal Yaw Degree : +51.30
Gimbal Pitch Degree : -17.70
Flight Roll Degree : +9.00
Flight Yaw Degree : +53.50
Flight Pitch Degree : +9.10
Cam Reverse : 0
Gimbal Reverse : 0
Self Data : Undefined
---- XMP-crs ----
Version : 7.0
Has Settings : False
Has Crop : False
Already Applied : False
---- MPF0 ----
MPF Version : 0010
Number Of Images : 2
Image UID List : (Binary data 66 bytes, use -b option to extract)
Total Frames : 1
---- MPImage1 ----
MP Image Flags : Representative image, Dependent parent image
MP Image Format : JPEG
MP Image Type : Baseline MP Primary Image
MP Image Length : 8737445
MP Image Start : 0
Dependent Image 1 Entry Number : 0
Dependent Image 2 Entry Number : 2
---- MPImage2 ----
MP Image Flags : Dependent child image
MP Image Format : JPEG
MP Image Type : Large Thumbnail (VGA equivalent)
MP Image Length : 244754
MP Image Start : 8737445
Dependent Image 1 Entry Number : 0
Dependent Image 2 Entry Number : 0
Preview Image : (Binary data 244754 bytes, use -b option to extract)
---- Composite ----
Aperture : 4.5
GPS Altitude : 31.3 m Above Sea Level
GPS Latitude : 31 deg 25' 55.75" S
GPS Longitude : 152 deg 54' 7.84" E
GPS Position : 31 deg 25' 55.75" S, 152 deg 54' 7.84" E
Image Size : 5472x3648
Megapixels : 20.0
Scale Factor To 35 mm Equivalent: 2.7
Shutter Speed : 1/200
Circle Of Confusion : 0.011 mm
Field Of View : 73.7 deg
Focal Length : 8.8 mm (35 mm equivalent: 24.0 mm)
Hyperfocal Distance : 1.56 m
Light Value : 12.0
===============================================

 

[sar104]

pardon my lack of knowledge as I'm new to this stuff.
Exif I refer to is from the Jpeg, and I can only see One altitude info.
attached is what I see.

you mentioned that "The DJI EXIF data contain both GPS MSL data and barometric altitude ".

where can you see them both ?

As mentioned in the previous post, ExifTool is one of the common programs for extracting detailed EXIF data. That's the one I use. There are also a few GUI's built around that tool, such as ExifExtreme.

 

[OneTenthOfaMileHighClub]

Whilst I have been 'flying' for just on a year, the first time I have taken any real interest in the Exif data of the images from the Phantom was to supply a friend with the altitude (against 'some' reference point), for the image/s taken. To be honest, I just assumed that ONE of the potential reference points of altitude was likely to be a height above sea level, as (I assumed) would be available by evaluation of the triangulation of the GPS satellite data from multiple satellites. (This is done by many 'hand-held', and 'off-road' style GPS units)

Another potential reference being the 'launch' altitude, was one that I really hadn't considered. To be honest, as far as the 'Authorities' are concerned, the height of the take-off point is useful, but the flying height above current "land-level" is what is enforced?

My comments on the data from the ExifTools program which gives a "Relative Altitude" (which is consistent with Take-Off altitude as 'Zero' altitude). However the "Absolute Altitude" of about 31m is not consistent with the fact that the take-off ground level was perhaps 3-5m above the ocean level as visible in the image, so that any accurate "Above Sea Level" figure might have recorded perhaps about 80m ASL, not 31m as recorded.

I am sorry that I don't really have much more info that the above!!

Best Wishes

(Exif Data below is as per original text)

---- GPS ----
GPS Altitude Ref : Above Sea Level
GPS Altitude : 31.371 m <<<<<<

---- XMP-drone-dji ----
Absolute Altitude : +31.37 <<<<<<<<<
Relative Altitude : +75.30 <<<<<<<<<