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What applications will show me altitude in metadata?

Discussion in 'Pro/Adv Discussion' started by jephoto, Jul 6, 2016.

  1. jephoto

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    Besides Lightroom???
    Up until recently when I view all my raw files in Lightroom, Grid view, I've been able to see the Altitude each shot was taken at- accurately.

    But last few weeks it's been showing me really wacky readings. I took some sunset shots last night at a harbor and the last set I did I was shooting some boats coming in with people on the jetty behind, silhouetted by the sunset. I know I was shooting between 25-50 feet for a lot of them. Had to be careful not to hit the mast of a sailboat a couple of times.

    But Lightroom metadata is telling me I was at 650 feet! No way.... And all I've shot recently seems to be showing way high altitudes.
    I mostly keep it under 400' theses days anyway.
    But last night I know I was very very low.
    What might cause Lightoom to give these wacky readings and what other software (Mac OS) may give me true readings?

    Photo Mechanic does not seem to show altitudes.


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    #1 jephoto, Jul 6, 2016
    Last edited: Jul 6, 2016
  2. Meta4

    Meta4 Moderator
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    The problem is that DJI (for no reason that makes any sense) decided that from Firmware 1.5 on, they would show GPS altitude data in the Exif info for each jpg file.
    But GPS altitude is totally useless and can be +/- a couple of hundred feet and change up and down during the time of a flight.
    The GPS data is also above sea level.
    I'm told that shooting raw still gives you barometer altitude data.
     
  3. jephoto

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    Well it used to. I realize now that these sacked readings probably started after I recently did a firmware & software update to latest everything. Maybe 3 weeks ago.
    I just imported one of my ground level shots into a new folder- bird is on the ground, after map has updated just before takeoff.
    Altitude shows I'm at 618.9'

    Maybe that's above sea level? I am in the Midwest- now in Michigan. If I subtract 618.9' from the 650.3 showing in the file I was talking about gives me 31.4'- which should be exactly right!!!
    WTF? How do I fix that????
    Is there a way to Zero the altitude setting before takeoff??


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  4. jephoto

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    Also, I know when shooting DJI Go was showing me the accurate altitude- 0' on the ground, and accurate heights while shooting. But what's now recorded apparently in the raw file is 618.9' higher.
    Crap.


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  5. jephoto

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    Update. Website <http://veloroutes.org> tells me the altitude above sea level at New Buffalo, Mi is 613'
    One mystery solved. Now how do we get the accurate data from out take off point? I don't want the FAA goons at some point looking at my images and going "Ah Hah!! You were shooting at 873' feet!! Fined $10,000!" When I'm really at 211'.....



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  6. jephoto

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    I'm going to start a new thread about this as this one is titled about what apps will show the data. It's really about how to get it to read or write the actual data. I want some input from DJI


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  7. Meta4

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    The FAA aren't going to look through your photos and they well understand the difference between AGL and ASL.
    That's one thing you don't need to worry about.
     
  8. jephoto

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    Well, that's good. But I still want to have my accurate altitude recorded. It used to....

    Is it the same for everyone now- absolute altitude from Sea Level only??
    Why isn't recording the numbers we see in the Go app when flying?

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  9. matti

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    AFAIR the video caption .srt file (I usually have it OFF) shows the barometer reading vs homepoint (not sea level).

    For my recent .dng files GraphicConverter (OS X) shows EXIF data as (Lightroom shows the same info):

    GPS Altitude: 545 m Above Sea Level

    or:

    Altitude reference: Sea level
    Altitude: 545.1m
     
  10. jephoto

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    Thanks Matti- that's what I thought. Don't understand why they can't give us both.
    I anlyse my shots for returns to the same location and want to know ( without a lot of math and conversions ) what my AGL was so I can know the most effective height for a given spot.
    DJI- please give us the AGL figures back!!!


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  11. jephoto

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    OK then. Weird thing. When I first started this thread I was pretty sure that my metadata was showing me the MSL - or elevation above Sea level. And a whole bunch of shoots I did here (Chicago) , Michigan and rural Illinois seems to bear that out. The Altitude showing in Lightroom's EXIF data pretty closely correlated to the elevation of that place in the US.
    So, on the beach at lake Michigan in Chicago I was getting roughly 575' give or take 20 depending if I was on the beach or off Lincoln Park on the grass. Etc.
    In Rural Illinois I was getting ground elevation near 900'. And then all my shots went UP from there.

    But today I updated my 2nd P3 that just came back from repair and took both to the park near my house.
    Website called What is my elevation? - very useful - says that at the park I should be at 597' above sea level.
    But my on the ground shots on BOTH drones now say 324.5' (the .5 I think was for the Pelican case I launched from....)
    And all shots went up from there. So when I read on screen I was at 270.3', the metadata now shows I was at 594.8'

    WTF is this now? Where did 324.5' come from?
    I used the same iPad for both. Most current (just reinstalled yesterday) version of Go. and latest firmware - 1.9.060
    Now I do also connect a Dual xGPS 150A Bluetooth GPS device to get a more accurate home point lock, But I've been using that for 10 months now and again- until last FW update all my altitudes read normal.

    Does ANYONE have a clue whats going on here?
    Here are some sample pairs of files- DNG+JPGs from both before and after the update.
    Dropbox - 07.12.16_DJI_sample_files
    I'd appreciate it if someone can tell me how to fix this. I know theres a bunch of big brains out there. Help me out.

    And yes, I have sent work to DJI to see what they have to say. But I really need to understand whats happening.
    And again - when getting Home Point and flying it displays on screen normally - 0' to whatever. But that's not what shows in the file info.

    Am I the only one this is going on with? Or is it the same with everyone and you all are just saying - "That's the Way It Is now."...?
    Really is just WRONG. I want to see the altitude from MY ground level that I was flying at. Period.
    When I'm at the G-**** sea, then from Sea Level will be fine........

    But at least I did fix the all of Chicago NFZ thing. That was a corrupted Go app. Grateful for that.
     
    #11 jephoto, Jul 20, 2016
    Last edited: Jul 20, 2016
  12. Meta4

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    The problem is that GPS is really, really useless for altitude data.
    It isn't just inaccurate, it is also changing all the time by significant numbers.

    Here's what Garmin say about GPS altitude (in)accuracy:
    How accurate is the GPS elevation reading?
    GPS heights are based on an ellipsoid (a mathematical representation of the earth's shape), while USGS map elevations are based on a vertical datum tied to the geoid (or what is commonly called mean sea level). Basically, these are two different systems, although they have a relationship that has been modeled.

    The main source of error has to do with the arrangement of the satellite configurations during fix determinations. The earth blocks out satellites needed to get a good quality vertical measurement. Once the vertical datum is taken into account, the accuracy permitted by geometry considerations remains less than that of horizontal positions. It is not uncommon for satellite heights to be off from map elevations by +/- 400 ft. Use these values with caution when navigating.

    Here's an example of how this works out in the real world.
    I made this GPS track from a Boeing 737 taxiing around a dead flat runway over a 1 minute period.
    [​IMG]
     
  13. sar104

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    If you were in the cabin then that is not a fair test of the system - the fuselage blocks GPS signals very effectively, and you are limited to those that you might have line of sight to out of a window. Since those are likely all in the same general direction, accuracy, especially vertical, is always poor.

    The situation is quite different in the open, and especially from an aircraft with an unobstructed view of the sky. In that situation, vertical accuracy is generally within 20 ft, and better for a high-quality chip.
     
  14. jephoto

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    So what changed in June? All my shoots for the past year, since I got my P3 last July always had relatively correct altitudes. 0' on the ground and as far as I can tell all the relative heights were correct.
    Now it's all wacky.
     
  15. jephoto

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    Also- no one still has answered my question- is the also happening to all of you- or is it just me?
    Anyone?
     
  16. Meta4

    Meta4 Moderator
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    There was a good satellite spread but as Garmin advise It is not uncommon for satellite heights to be off from map elevations by +/- 400 ft.
    I've stood on the beach and seen +/- 100 ft ASL readings on the GPS.

    What happened is that for some reason known only to themselves, after firmware version 1.4, DJI decided to replace the barometer derived altitude data that they had always used in the Exif info with the useless GPS altitude data.
    It's a big mistake on their part but all my contact with DJI people gets the same response ... that's how they want it.
    If you have firmware version 1.5 onwards, you get the useless GPS data in your Exif info.
     
  17. sar104

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    I can guarantee that you did not have a good satellite distribution from within an aircraft main cabin. It's not physically possible.

    As for seeing those kinds of variations under good conditions, such as might be expected on a beach, I have no idea why that would be - maybe you are using old equipment. I haven't seen those kinds of vertical errors with reasonable reception for many years. Hardware has improved, and the full constellation of satellites is available. Even without dual frequency reception, modern WAAS-enabled units should typically achieve +/- 5m vertical. Garmin's guidance is overly conservative, and we just don't see those kinds of errors in real use.
     
  18. Meta4

    Meta4 Moderator
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    Unfortunately WAAS is only available in North America - that could be a contributing factor.
     
  19. sar104

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    Good point - if you don't have access to L2 or any DGPS data then that will hurt accuracy.
     
  20. matti

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    To check the reliability of the altitude data I ran a test today (P3P FW V01.09.0060, DJI GO 3.0.0 , iOS 10.0.2, iPad Pro 9.7").

    I initially thought that with the current FW the EXIF altitude data was from the unreliable GPS while the barometer altitude data in the video caption .srt was correct. It seems i was wrong about the EXIF.

    The result: all EXIF, EXIFTool and .srt altitude readings were spot on within 1m error margin.

    To get the correct altitude vs homepoint from the .jpg and .dng I had to have an image taken at the homepoint, though.

    I was surprised to find that the EXIF altitude data was spot on (after subtracting homepoint EXIF altitude data from the AC EXIF altitude data).

    I wonder why Google Earth reports 50m for the homepoint while .jpg and .dng EXIF data for it is 192m?

    ...

    Google Earth Pro homepoint altitude 50m.

    DJI GO homepoint altitude 0m.

    I then took .jpg, .dng and .mp4 footage at 0-30-60-120-240-480m altitudes reported by the DJI GO.

    I checked the .jpg and .dng EXIF altitudes with GraphicConverter 9.7's EXIF and EXIFTool and .mp4 .srt altitudes via a text processor.

    P3P homepoint altitude readings at ground level were all the same:

    .srt:
    BAROMETER:0.0

    .jpg EXIF:

    Altitude reference: Sea level
    Altitude: 192.7m

    .jpg EXIFTool:

    GPS Altitude Ref: Above Sea Level
    GPS Altitude: 192.693 m
    ---- XMP-drone-dji ----
    Absolute Altitude: +192.69
    Relative Altitude: +0.00
    GPS Altitude: 192.6 m Above Sea Level

    .dng EXIF:

    Altitude reference: Sea level
    Altitude: 192.8m

    .dng EXIFTool:

    GPS Altitude Ref: Above Sea Level
    GPS Altitude: 192.764 m
    ---- XMP-drone-dji ----
    Absolute Altitude: +192.69
    Relative Altitude: +0.00
    GPS Altitude: 192.7 m Above Sea Level

    I subtracted the EXIF and EXIFTool AC altitude reading from the homepoint reading. .srt barometer readings were spot on.

    Google Earth reports 50m altitude for the homepoint.
     
    #20 matti, Oct 1, 2016
    Last edited: Oct 1, 2016