Exif - Script Writing - CHDK Forum
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Exif

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Offline dcshrum

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Exif
« on: 13 / October / 2010, 14:41:57 »
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I have a 780IS.  I'd like to embed geolocation information in the image using the exif format.

As the 780IS does not have an embedded GPS I'd need to pull the location information via the USB connection.

Is it possible to push current coordinates to a file on the SD card for reading via a CHDK script or pull coordinate data via the USB connection?

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Offline reyalp

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Re: Exif
« Reply #1 on: 13 / October / 2010, 15:58:40 »
In the normal CHDK builds, there is no data communication to CHDK using USB. The experimental PTP builds could theoretically allow you to do this, assuming you have a USB host that understands PTP providing the GPS data. In practice, this would probably have to be a PC. You could not connect most standalone GPS devices to a camera, since neither one is a host.

You can roll your own communication using the USB power signal, but that requires whatever is on the other end to be able to control the USB power. A suitable programmed micro-controller could translate serial data from a GPS this way.

A much simpler solution would be to log your GPS data separately and add the geolocation data after the fact based on time stamp. I'm sure there is something off the shelf to do this with standard GPS logs. Depending on what you are doing, you may need to account for clock drift on the camera somehow, but I expect this wouldn't be needed for most applications.
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Offline dcshrum

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Re: Exif
« Reply #2 on: 13 / October / 2010, 16:18:11 »
I am currently logging the data externally and I'm using an ardunio micro-controller so I could use PTP.  I'll read around a bit on PTP and CHDK.  Thanks for the pointer. 
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Offline reyalp

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Re: Exif
« Reply #3 on: 13 / October / 2010, 18:16:03 »
Quote from: dcshrum on 13 / October / 2010, 16:18:11
I am currently logging the data externally and I'm using an ardunio micro-controller so I could use PTP.  I'll read around a bit on PTP and CHDK.  Thanks for the pointer.  
A microcontroller will probably not do PTP. It could let your roll your own (one way) communications using the USB power signal. You will probably need some communication in the other direction (to tell the microcontroller that you are ready for GPS data), which you can do with an LED. Search on the forum should bring up some similar projects.

edit: for reference,
the ptp thread is here http://chdk.setepontos.com/index.php/topic,4338.0.html and wiki page is here http://chdk.wikia.com/wiki/PTP_Extension

I hope to have some variant of this in the trunk in the relatively near future.
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Offline SkyWalker9

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Re: Exif
« Reply #4 on: 13 / October / 2010, 18:36:38 »
Quote from: dcshrum on 13 / October / 2010, 16:18:11
I am currently logging the data externally...
In that case, there are a number of apps that you can use to transfer the geo data to your photo EXIF. The apps that I use with my Garmin are EasyGPS and Gpicsync (both freeware). Recommend reading the "Getting Started" from the Gpicsync web site...

The new EXIF section looks like this:

GPS
  GPS Latitude Reference        North latitude
  GPS Latitude                         41.49' 25.77"
  GPS Longitude Reference     West Longitude
  GPS Longitude                       86.22' 47.8668"
  GPS Altitude Reference        Sea level
  GPS Altitude                          210.188m
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Offline Pauls9

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Re: Exif
« Reply #5 on: 14 / October / 2010, 04:26:05 »
Another program is Prune ( http://activityworkshop.net/software/prune/index.html ), which runs under Java. Also displays the tracks on a map.
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