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by Joel Cusick, National Park Sevice, Alaska Regional Office
Right-click and choose Save as to download the Sony GPS-Camera Review
As an ardent fan of all things Geotagged, I wanted to share with you some
observations with one of the consumer digital cameras on the market today
with an integrated GPS and compass versus the features and accuracies of a
"mapping" grade photo system.
Ingredients
- Sony DSC-HX5V digital camera
- Garmin Map76CSx set to Tracklog
- Trimble GeoXT 2008 w/ TerraSync 4.1 and DDF with a file name attribute for associating photos
- Trimble TrimPix Professional
- Trimble Pathfinder Office
- Geospatial Experts GPS Photolink Version 5.0 for watermarking and analysis
Background
I recently purchased a Sony DSC-HX5v digital camera with embedded GPS and
compass. It has SDHC memory capacity so TrimPix can be used. This is new
for Sony to offer a non- propiertery Sony Memory stick as a storage option
(finally). As GPS/GIS professionals, we are being asked to evaluate and
recommend GPS-integrated cameras for use in GIS applications. I'm the
first to welcome these integrated technologies to expedite the geoposition
of photographs however, there are considerations when we think about
features (points) being mapped with attributes and the photo subject (the
thing you are mapping). For certain jobs (aircraft or scenery overviews or
preliminary trail layout), an integrated GPS/Camera may serve really well
as a first look. I've been using the Ricoh 500SE for years, and consider
that camera top-drawer for GPS integration and features not found in the
consumer line. It's just that many folks complain about cost, size, and
why bother when you can get a camera/GPS/compass all in one. I have some
comparisons that highlight issues that should be raised and considered with
such systems.
Overall thoughts on the camera
I really like the Sony. A price point of about $350 was right for me. The
compass is quite good (after calibration) and responsive. Magnetic only (no
declination). Battery life is good. I bought an extra spare, and shot 150
photos over 6 days with plenty of energy to spare. Will not accept AA. The
GPS is on top on left side of camera away from your finger over shutter
(good idea eh?). The GPS takes from 5 seconds to 3 minutes to "acquire".
GPS display is reduced to showing one to three bars (coords not shown). If
you had the camera on within 30 minutes, the acquisition is under 1 minute.
I always held camera up above head to maximize time to acquire (a photo
stance for the future), but even under moderate canopy, acquiring signal
takes time. Sometimes turning on/off camera helps. There is nothing to
show that you have a fresh GPS position except 3 signal bars. If you don't
wait to get a signal bar, the previous position will be used to tag photos.
All photos will be tagged in even if you show no signal. You can turn off
GPS (stop tagging), but getting to the menu to turn off GPS is about 10
clicks. There is an EASY button setting that makes the GPS from menu
accessible to turn off quickly though. There is no feature to "LOCK" GPS
onto the photo subject, then step back and take the photo from the
photographers position.
Accuracy
A few tests in various Alaskan country shows the Sony works pretty good in
the open Slide 4 (range of 2-5 meters), but under canopy error budgets
increase dramatically Slide 5 (witnessed 200 meters). The open sky
environment is adequate for these systems. That's a picture of Denali -
North America's tallest peak from Denali State Park. Wonderful shot!
No GPS position is better than a really wrong one
Since this camera tags all photos regardless if the GPS has a hot fix or
not, you can tag a photo miles from it's position. A habit of mine is to
turn on the camera, shoot the photo and turn off camera to conserve battery
life. Unless you give these camera's time to fix, you can embed extreme
inaccuracies, harming a mapping project more than it helps. I would much
rather not have any gps position than a really wrong position.
Inability to Offset from a Photographers Position
Again, no big deal if you in an aircraft shooting photos where you don't
mind having the position of the camera coordinates embedded, but a bigger
deal when on the ground and tying the photo to a feature. Tying the
photo of the subject (the feature) to the feature is important to reduce
map confusion and matching photo management.
Slides 6, 7 and 8 show a scenario where offsets come into play. The Sony
(Slide 6) cannot determine an offset, plus it has inherent accuracies that
place the photographers position in errors of 10 - 30 meters away from true
photographer position. While the Trimble (Slide 7) has the ability to
offset and "bind" one or more photos to a particular point feature. In
this case, I took 2 photos (1 and 2) of a building, and associated those
photos using TrimPix to a building primary entrance point feature. I took
another photo of a sign along the west side of a road and associated that
photo with a Sign point feature. In the first mapping scenario I want all
photos assigned to one coordinate - the primary entrance. Turn to Slide
8. Hence, i will stand off from the building, offset the GPS antenna
position to the front door and fire my photo. This way I conserve energy,
and maximize efficiency by mapping and shooting from the same spot. I then
Paused the Feature, walked around to back of building and took my Photo 2.
TrimPix sent both photos to my datalogger and i selected both photos and
closed feature. I then opened my Sign Point feature, offset the point to
the sign, fired my photo, wirelessly transmit my photo via TrimPix, and
close feature. In Slide 6, you can see the result of all photos.
Watermarking from GPS PhotoLink stamps the photos with the Postprocessed
Exported true position of the GPS. Coordinates are blocked to protect the
innocent (:><).
Having GPS PhotoLink to handle all the final photo processing is still valuable
for seeding true Differential positions from an export back into the photo,
watermarking and file management of the photo batch
Can You Have a GPS Camera and TrimPix?
Sure! Any camera with a GPS most likely is SDHC compliant. Hence, TrimPix and a GPS
embedded camera serves as a backup to a workflow. TerraSync overwrites
the in-camera GPS positions on photo association to the feature, but having the raw
gps photo can serve as a backup in case things go really wrong in the field.
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Joel Cusick
National Park Service/Alaska Regional Office
240 West. 5th Avenue, Anchorage, AK - 99501
(907) 644-3549
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+61°13.0213', -149°53.1763', (NAD83 CORS96)
6VUN4499490383 USNG
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Many thanks to Joel for his never-ending enthusiasm and support! |
GPS-enabled photos
