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Data Logger (of sorts) for GPS

Discussion in 'Electronic Design' started by [email protected], Jun 3, 2007.

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  1. Guest

    Hi All,

    I have recently built a GPS receiver which attaches to my camera
    (Nikon D200).
    When locked on, the co-ordanates are embedded in the image file.

    This all works well - except...

    When in built up areas, the lock is lost and as such, No info provided
    in image.
    I would like to kill two birds with one stone here.

    I have found a small, compact logger from Sparkfun.com which will log
    to a SD card and can use this.
    However, I would like to add the functionality that should the lock be
    lost, it should continuously send the last known co-ordinates to the
    camera.

    How might I go about doing this?

    Some constraints are:
    - Size - I am limited to space as I would rather not have a huge box
    stuck to the top of the camera
    - Power - Already, the GPS, MAX232 and the fact that the camera does
    not go into standby when GPS available, drains the camera batteries
    rather quickly.

    Any pointers would be appreciated.

    TIA

    Cheers,
    Crispin
     
  2. mpm

    mpm Guest

    Hello Crispin.
    I'm not familiar with the D200 that much. I have a D70, with a D50
    backup (as a spare).
    I'm curious, are you writing the coordinates directly to the camera's
    flashcard memory (on mine, its CompactFLASH on the D70, and "SD" I
    think? on the D50).

    If so, I'm wondering how you get access to the card slot....?
    Or are you doing some offline data storage (in your GPS device) and
    then merging the data later in sequential shot-take order?

    FYI, I was wondering when consumer grade cameras would get GPS
    capability.
    I was at an SBE meeting last year (Society of Broadcast Engineers),
    here in the US and Sony demo'd one of their new digital HD cameras -
    for broadcast news trucks and the like...
    Unpaid plug: FANTASTIC CAMERA by the way, that is if you have $70,000
    budgeted...

    It had a GPS option built-in, and it was tightly coupled to the
    camera's "Digital Rights Management" capabilities. Both location and
    local time were encoded directy to the video's metastream.

    I was just wondering how close your approach is to that, and secondly,
    if it would be worth it (to me) to do something similar with either my
    D70, or less likely, the backup D50.?

    As to your question about small, low-power solutions, the Phillips
    LPC903 chip comes to mind.
    It's an 8-pin 8051 derivative, lots of low-power and idle modes,
    etc.., and supports serial RS232. It even has an interrupt for
    RS232. I don't recall if it comes in a DIP, but I know it comes in
    SOIC. Some of the Phillips LPC90x come in both flavors but one of
    them doesn't. You'll have to check.

    Admittedly, it's not my favorite microcontroller, but given space and
    power constraints, it's probably worth a look. Good luck. -mpm
     
  3. He nneds an controller with 2 UARTS to have this board
    between the GPS and the camera. Don't forget to
    increment the time in the NMEA stream

    Rene
     
  4. Guest

    Hi mpm,

    The D200 natively supports GPS capture in the EXIF for each file.
    The one I have built uses a gutted GPS receiver I bought of ebay and a
    levels converter (MAX232) which is housed in a small box which mounts
    to the top of the camera (Hotshoe)
    It then plugs into the 10pin socket on the D200.
    An example of it's use:
    http://crispin.smugmug.com/
    and the gallery: http://crispin.smugmug.com/gallery/2836753#151905852

    See the google plugin for GPS location of pics.
    It is all housed in a nice little box (http://www.maplin.co.uk/
    Module.aspx?TabID=1&ModuleNo=1681&doy=4m6)

    During testing, it worked well - however...
    During a recent trip to Italy and real life use, I found the following
    issues:
    - Power.
    She be hungry and flattens two batteries in a couple hours of
    shooting. This is due to a number or reasons. The GPS, the converter
    and mostly, the fact that the camera does not turn off metering when
    it is receiving a GPS signal.
    - Lock loss.
    Walking around built up areas it looses it's lock and as such, data
    not logged. For this reason, I want the added functionality mentioned.
    - Logging.
    I would like to log the data onto a separate card for later use.
    (Google Earth)
    - Did I mention Power?
    I am looking at an option for a small Li-ion battery to power the GPS
    alone and not rely on the camera power.


    I am not aware of any options for the D50/70 directly but have seen
    some applications which will take GPS logs and merge the info with
    images at a later stage based on file times.

    If you have a scratch around google you'll find a number of solutions.
    I'll stick stuff up on mine shortly (Time permitting).
    Mine, if I may say so myself, is by far the prettiest solution I have
    seen on the net :) Small and neat where as other have numerous cables,
    D9 plugs etc etc. Ugly.
    My only drawback is that I cannot use the flash when GPS is mounted.


    Cheers,
    Crispin
     
  5. mpm

    mpm Guest

    Those are some fantastic images on your gallery!! Really nice work!
    Especially the ones taken in Monoco.

    I'll have to re-visit when I have some more time.

    I was pretty sure the D70/D50 was a no-go for GPS.
    I did see a battery handle extension that had a GPS port, but it was
    really pricey, and I think you had to slave off an SC-28 or something
    like that. (Not my style - too many cords).

    You know, if you're not doing too much hiking, etc.., a battery belt
    would surely do the trick.
    Not sure if you want to tackle all that weight??

    As for GPS lock, that's a bummer. How often does it go out of lock?
    Do you think it could be an antenna issue? Of do you just think it
    can't see the satellites?
    I wonder how many satellites it can track at once. The good GPS's
    I've seen, (like some of the Garmin units) can track up to 12 birds at
    a time. This might be common, however, with other brands.

    Also, a bit of trivia. I once tried to work out time differences
    using two remote GPS units. It turns out that each unit needs to see
    the same constellation of satellites and be using them in their
    position calculations or you can resolve the position effor any better
    than the estimate error shown on the screen(s). Obviously, in my
    test, the GPS's were each using a unique set of visible sats. -- that
    little project took me several weeks to figure out what was wrong!!
    (I was sure it was in my math!) Oh well, live and learn.

    I think the near-term solution is (if I decide it's important enough)
    to just keep a log of GPS readings and then add them in the EXIF data
    manually when I download the photos. It's not ideal, but it will
    "eventually" give me a reason to upgrade my digital outfit.

    Good luck with the power budget problem.
    If you can get the D200's metering to cooperate, you'll be more than
    halfway there I suspect!

    -mpm
     
  6. Guest

    Hi Rene,

    Thanks for the reply but could you clarify a bit.
    I'm a noob at this... :)

    Regards,
    Crispin
     
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