Posted: Wed Mar 12, 2008 4:47 pm
slug wrote:nolock:
Glad to see you noticed this already.
I've been looking at your photos while testing the maps feature since many of your photos already had GPS data in them.
Especially interesting since they have altitude data. Looks like a lot of fun flying around with a camera.
We're fixing the lat/long entry boxes to accept other formats besides decimal.
But I'm going through your photos right now and expect about 800 of yours to be mapped in a few minutes.
Hope you won't mind if I post a link to http://maps.pbase.com/nolock so other people can have a look.
Curious to know what hardware/software you used to get the GPS data into your JPEGs.
-slug
I was not doing geotagging prior to last May 2007, so photographs older than this will not contain the geotag data. All the images in these galleries are geotagged. Note that the geotag data is only contained in the 'original' versions.
http://www.pbase.com/nolock/homathko
http://www.pbase.com/nolock/compton
http://www.pbase.com/nolock/lillooet
http://www.pbase.com/nolock/qbesschilko
Here is a summary of how I geotag my images. I am not a geotagging expert by any means, but this system has worked well. It was not designed for aerial photography, and in this application I estimate accuracy of perhaps a tenth of a mile or less. 'Absolute' accuracy would cost many thousands of dollars (maybe as much as a hundred thousand, for the various gps equipment, autopilots, computers, etc.). I don't need that kind of accuracy.
I use the Sony GPS-CS1 device. It is one of several GPS track-file recording devices. It may not be the best one - there is at least one other right now that is cheaper, more sensitive, and records more track points.
Here is a list of devices, with reviews: http://scilib.typepad.com/techreviews/reviews-list.html
There are a few important points about accurate geotagging.
- The camera clock has to be set to "GPS" time. This is the time the gps is picking up from the satellites. If this step is not taken, the geotag data will not be accurate when the images are geotagged. Camera clocks tend to 'drift' a bit, so I reset the camera to gps time at least once during each flight, just to be safe. The Sony GPS-CS1 does not have a display, so you need a separate GPS unit with a display, that can show "GPS" time. Then manually set your camera to that time, as near as possible (nearest second would be best). This is slightly tricky but with practice you can be quite accurate.
- in general, the track recorder needs to have a clear view of the sky. Heavy forest canopy, or indoors, or among tall buildings, tends to inhibit/block the signal and degrade accuracy. The recorder may lose satellite contact altogether. In my situation, I use a bit of velcro to hold the device in place on top of the instrument panel glareshield, where it has a 360 deg view of the sky in normal level flight. The GPS-CS1 has a carabiner loop, so you could let it hang from a pack, say. Personally, I'd prefer to have it sitting up high so it would be more accurate (as opposed to hanging it from a belt loop, for example).
- I have not verified the accuracy of the altitude data. I have noted that in my case, it seems to definitely be in the ballpark, but I have not taken the time to write down and compare my indicated altitude for certain photographs.
- When I return from a flight and download/geotag images to the computer, I use Breeze System's 'Downloader Pro': http://www.breezesys.com/ - This outstanding software does the job quickly and accurately. The GPS-CS1 is first connected to the computer via USB cable. Then the CF card is inserted into the card reader. Downloader Pro compares the track file to the image time, and imprints the appropriate lat/long/altitude into each image. It interpolates the position if an image falls between two track points. This has proven quite accurate. Downloader Pro is not the most intuitive program to use, so make sure you are getting good geotag accuracy before you erase your storage cards. Make sure you know what time zone you are in, whether you are on daylight savings time or not, etc., so you will be able to enter the correct values in the GPS settings box in Downloader Pro. Copy and save the track log files from the recorder to a folder on your computer. You may need them again if something goes awry. Downloader Pro will create a Google Earth kml file from your track files, and it is interesting to look at these tracks in Google Earth. (another option for geotagging software: http://www.robogeo.com/home/ - this program seems to get good reviews in the various forums).
- Breeze System's 'BreezeBrowser' software does a good job of displaying EXIF (and geotag) data. However, I am am an Irfanview devotee (http://www.irfanview.com) for viewing EXIF and viewing geotagged images in Google Earth. Irfanview is free, highly capable, and fast. The "view this image in Google Earth" feature is terrific. This is found in the 'Image - Information - EXIF' panel when looking at an image. You must download and install all of Irfanview's plugins to have this feature. The plugins are free as well.
One of the big pitfalls of geotagging and GPS right now is that there is no industry standard for track file formats. So if you have different brands of tracking devices or GPS units with downloadable track files, you could very well run into difficulty trying to geotag your images. I cannot offer a good solution to this problem, other than to point you to http://www.gpsbabel.org where you will begin to get an idea of the difficulties of this issue.
This summarizes my approach. Hope that it may be helpful. It sounds complicated, but in practice, it has proven to be fairly simple.