iPhoneography -- that is, digital photography using the Apple iPhone built-in digital camera -- rekindled my interest in photography. A couple of years and three iPhones later, I'm eager to experiment with more capable digital cameras such as my old Canon PowerShot G9 and my new Panasonic Lumix DMC-FZ150. I will continue to use my iPhone camera along with many excellent third-party camera-replacement and photo-editing apps, but from this point forward waltersanford's photoblog will be no longer dedicated to iPhoneography exclusively. I hope you will continue to follow my photoblog as I explore exciting new directions in digital photography and videography.

The North American Sundial Society Sundial Registry listing for Virginia Alexandria Dial #253 says, “May have been removed; could not be located 8/2005. Contacted historical society 12/2008 to confirm placement but no reply.” I’m happy to report the sundial is in fact right where it’s supposed to be! Well, sort of. The Sundial Registry lists the location of Dial #253 as, “NW corner of King & Cameron St.” That is, in a word, impossible: Cameron- and King Streets are parallel streets, as shown by a zoomed-in map of Old Town Alexandria. The actual location of the vertical sundial is the corner of Cameron- and N. Washington Streets, as shown by a geotagged full-size version of the photo and verified by the following screen captures from Google Maps Street View: facing east along Cameron Street toward N. Washington Street; corner of Cameron- and N. Washington Streets; facing west along Cameron Street toward N. Columbus Street.

Alexandria Dial #254 is a horizontal sundial located at historic Christ Church on the opposite side of Cameron Street from Dial #253. The Sundial Registry listing for Dial #254 says, “Horizontal circular bronze dial appears to have been designed for 32 degrees N.” Read more about this issue in my last post, "Sundial at Christ Church, Alexandria, VA USA."

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Picasa Web Album: Alexandria, VA Sundials

Tech Tips: All photos in the preceding slideshow were geotagged automatically by an Apple iPhone 4. Apple Computer does not support Adobe Flash on its mobile devices, so embedded slideshows from Picasa Web Albums (such as the one shown above) will not display properly on the iPod touch, iPhone, and iPad. For this reason, you may need to follow the hyperlink to the photo album, then click on the slideshow icon (shown upper-right corner). Learn more about Google Maps Street View. Locate the sundials using the following search string in Google Maps: "Christ Church Alexandria"

A horizontal sundial is located on the grounds of historic Christ Church in Old Town Alexandria, Virginia USA. The North American Sundial Society Dial Registry listing says, the "dial appears to have been designed for 32 degrees N." In order to determine whether the sundial is in fact aligned properly, I examined a couple of photos that were geotagged by my Apple iPhone 4. (See "Tech Tips" for details, below.)

Similar to setting the correct time on an analog clock or wristwatch (by moving the hands of the timepiece into proper position), properly orienting a horizontal sundial will move the shadow of the gnomon (or style) into position so that the dial face displays the correct time.

1. The dial plate should be horizontal.
2. The shadow-casting edge of the gnomon should be parallel to the Earth's axis, inclined at an angle equal to the latitude of the sundial.
3. The tip of the gnomon should point toward the North Celestial Pole (i.e., Polaris, the North Star). More simply, the dial face should be aligned so that 12 noon points toward geographic north and the 12 noon hour line is aligned with your local meridian.

Photos 1-2 of 8 (shown below) verify that the dial plate is horizontal. Photos 3-4 show the gnomon is inclined at an angle of 31.86 degrees (~32 degrees); Photos 5-6 show the latitude of the sundial is 38 degrees 48 minutes 22.2 seconds. Photos 7-8 show the image direction is 218.4602 degrees, meaning the tip of the gnomon is pointing southwest rather than true geographic north (0, 360 degrees).

(download)

Click here to download:

sundial-at-christ-church-alexandria-va-usa-vksuFgqGhEjxwzoGgocm.zip (8.88 MB)

Bottom line: The Christ Church sundial appears to have been made for another location and is aligned improperly for its new location. In other words, the sundial is strictly ornamental and will not tell time correctly.

Tech Tips: The iPhone Camera app works seamlessly with two built-in devices to geotag photos: the GPS sensor measures position on Earth; the digital compass measures "image direction." PixelStick, an application for Mac OS X, was used to measure angles in one of the photos (see Photos 1-4, above). Apple "Preview" was used to display GPS info for both photos (see Photos 5-8, above).

Photos © Copyright 2012 Walter Sanford. All rights reserved. www.wsanford.com