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APPLE: Bridge distortion common in computer maps

Letter by Jerry R. Broadus, Puyallup on Sep. 24, 2012 at 2:08 pm with No Comments »
September 24, 2012 2:09 pm
Apple's new maps app displays the Narrows bridges as a collapsed wreck of concrete and steel. (Screenshot from Tumblr's "The Amazing iOS 6 Maps.")

The Saturday paper put the now locally famous screenshot of the Tacoma Narrows Bridge from the new iPhone system on the front page. I cannot comment on Apple Maps as a whole, but the distortion of the bridge in the photo appears to be nothing more than the result of using two photos for the bridge, and placing them on different elevation planes for mapping.

To accurately map a photo, you have to control elevations. This effect is common to other mapping systems as well.

You might try going to Google Earth, on a large computer screen, and zooming in to the Tacoma end of the same bridge. Get in real close, and then place the bridge approaches slightly off center. You will see that in the Google system the bridge appears to plunge down the slope to approximately the water level of the Narrows. Looks like a Nordic ski jump.

The satellite image in Google Maps (this time on an iPhone) shows a similar distortion, but it’s not as dramatic, probably because the program is not generally used for similar “fly throughs.” If, in Google Earth, you bring up the Astoria Megler Bridge, and then go to “street view,” you will not see even the rise over the shipping channel.

In short, to get fairly accurate distances on the level of these channels, the mapping program is reducing the photos to sea level. With the Tacoma Narrows, it makes the bridge look like a causeway rather than a suspension bridge.

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