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Photogeo Tip

FAQ #8 Accuracy

or “Why don’t the camera markers show up exactly where my feature is located?”

Issue: You take a bunch of photos and then go back to the office, import them using PhotogeoDWG. Gosh, the photos you snapped along a sidewalk show up in the middle of the road. Or worse, they are placed on the other side of the planet.

There are several reasons why this might be the case.

i) When you take the photograph, the camera will record the location of the camera. That is, where you are holding the camera at the time the photo was snapped.

ii) Location accuracy will be as good as the equipment you are using. A smart phone generally is accurate to within 10 meters. We were able to improve accuracy using a mobile wifi puck. You might also consider satellite enhancement dongles like the Bad Elf device for iPhones.

iii) Wildly inaccurate results could be due to interference of your GPS enabled device. Interference can be caused by tall buildings such as found in a dense city landscape, excessive tree coverage, and even cloud coverage.

iv) Imagery – google maps, bing maps are not as accurate as imagery you may have purchased. And you are not limited to using bing maps. Any background, including a CAD background can be used.

v) And, double check the GCS. As you might imagine, the wrong coordinate system will cause erroneous placement.