767
edits
Changes
Jump to navigation
Jump to search
Line 2:
Line 2: + + Line 19:
Line 21: +
Added images
==Fresnel Lens==
==Fresnel Lens==
[[File:System_III_Fresnel_Lens.png|frame|right|A Fresnel lens receiver is a cost effective alternative to a telescope, allowing a much larger aperture at reasonable expense.]]
The current receiver system uses a ~12" x 12" Frensel lens [http://www.wikiwand.com/en/Fresnel_lens], sold as a replacement part for overhead projectors. A Frensel lens employs complex internal geometries to mimic the optical properties of a conventional convex lens, while maintaining a thin plate shape. The effect of this is that a large lens can be made cheaply and does not occupy as much space as a traditional lens of similar aperture (i.e. the size of the inlet, which limits the amount of light a lens will allow to pass through). The Optical Comms team switched to a Fresnel lens receiver after demonstrating that the larger aperture allowed by the lens gave better light output to the photodetector over the conventional telescopes that had previously been used. Telescopes were cost limited to about a 6 inch aperture for the group, while very large Fresnel lenses could be easily acquired with some creative Craiglist searching (the largest of these came in the form of an old rear-projection television monitor).
The current receiver system uses a ~12" x 12" Frensel lens [http://www.wikiwand.com/en/Fresnel_lens], sold as a replacement part for overhead projectors. A Frensel lens employs complex internal geometries to mimic the optical properties of a conventional convex lens, while maintaining a thin plate shape. The effect of this is that a large lens can be made cheaply and does not occupy as much space as a traditional lens of similar aperture (i.e. the size of the inlet, which limits the amount of light a lens will allow to pass through). The Optical Comms team switched to a Fresnel lens receiver after demonstrating that the larger aperture allowed by the lens gave better light output to the photodetector over the conventional telescopes that had previously been used. Telescopes were cost limited to about a 6 inch aperture for the group, while very large Fresnel lenses could be easily acquired with some creative Craiglist searching (the largest of these came in the form of an old rear-projection television monitor).
==GPS Verification==
==GPS Verification==
[[File:Geodetic_survey_mark.png|frame|right|Geodetic Survey marks indicate locations that have been precisely located by the US Geodetic Survey]]
In order to investigate the accuracy of GPS measurements, which can potentially introduce another source of error, the group set out to locate several Geodetic Survey Markers [https://en.wikipedia.org/wiki/Survey_marker] near the usual 10km test sites. These marks indicate very precisely triangulated locations determined by surveyors for the US Geodetic Survey. The OpComms team was able to locate mark AA1874 [http://www.geocaching.com/mark/details.aspx?PID=AA1874], in the parking lot of the Skyline Boulevard test site, as well as nearby HT3252 [http://www.geocaching.com/mark/details.aspx?PID=HT3252]. By finding these marks, the group was able to confirm the accuracy of some of the GPS coordinates assumed by the MATLAB script. The group also purchased several mid-range quality GPS hand units to verify measurements, and found that in-field measurements were accurate to 4 decimal places in latitude and longitude, but were accurate to only 10’s of meters in altitude, due to the nature of satellite triangulation.
In order to investigate the accuracy of GPS measurements, which can potentially introduce another source of error, the group set out to locate several Geodetic Survey Markers [https://en.wikipedia.org/wiki/Survey_marker] near the usual 10km test sites. These marks indicate very precisely triangulated locations determined by surveyors for the US Geodetic Survey. The OpComms team was able to locate mark AA1874 [http://www.geocaching.com/mark/details.aspx?PID=AA1874], in the parking lot of the Skyline Boulevard test site, as well as nearby HT3252 [http://www.geocaching.com/mark/details.aspx?PID=HT3252]. By finding these marks, the group was able to confirm the accuracy of some of the GPS coordinates assumed by the MATLAB script. The group also purchased several mid-range quality GPS hand units to verify measurements, and found that in-field measurements were accurate to 4 decimal places in latitude and longitude, but were accurate to only 10’s of meters in altitude, due to the nature of satellite triangulation.
[[Category:Optical Communications]]
[[Category:Optical Communications]]