Camera Tilt-Down Phenomenon

Observation:

Since operation of the webcam began on September 19, 2005, the camera has mysteriously tilted downward - not just once, but twice.  Sometime between the time of the image taken on January 4, 2006, and the time of the image taken on January 5, 2006, the camera tilted down by about 2.5 degrees.  This happened again between 1 and 3 pm on March 23, 2006, when the camera tilted downward by another 3 degrees.  

You can see this change in the vertical field of view in the three images below.  In all three images, the top of the pole is at the same height from the bottom of the image.  Thus, the amount of the tilt-down can be determined by measuring the distance from the top of the pole to the top of the image.  In the series of images below, the bottom of the images are aligned, so you can see the amount of tilt-down that has occurred by how much the banner at the top of the image is displaced downward in each successive image.

Analysis:

The camera is secured to a flat plate within the metal camera enclosure holding it fixed in relation to the outside of the enclosure.  The enclosure is attached to the cabin wall mounting bracket with a "U" shaped steel frame with two 1/2" bolts into either side of the enclosure.  This provides for the vertical or elevation adjustment of the field of view.  The azimuthal adjustment is provided for by rotation around a 1/2" bolt between the bottom of the "U" shaped frame and the end of the wall mounting bracket.  Pointing around the azimuth axis has apparently not changed.)

The mass of the camera/enclosure assembly is not evenly distributed around the axis of the elevation adjustment bolts.  There is more mass at the front end of the assembly than there is at the back end.  This is because the camera itself is mounted at the front end of the enclosure against the enclosure's window, and the front lip of the enveloping plastic dog house extends about 4 inches out in front of the window.

Even though the dog house is rounded on the top to prevent snow accumulation, it is suspected that there is some accumulation that contributes to an even greater mass on the front end of the camera enclosure assembly.

By referring to the Snowfall table, it can be seen that January 5th and March 23rd were days of exceptional snow fall (23 inches in the days just before the 5th, and 14 inches in the days just before the 23rd) and low temperature (observed in the temperature log which is not posted on the website).

The tilting was probably the result of the lower ambient temperature causing the camera enclosure's elevation axis clamp to loosen slightly (as the metal contracted) and the weight of snow piled on top of the forward end of the camera enclosure dog house causing a greater torque on the elevation axis clamp.

Hopefully the mysterious tilt-down won't continue with the arrive of Spring and warmer temperatures!

4-11-06