My Lovely Sha Sha, latitude, and longitude

This term Binky was replaced by My Lovely Sha Sha 

My Lovely Sha Sha 

Complete with a name tag

The string proved very useful for securing Sha Sha to a branch

Location of Sha Sha to the west of the student center

Tied to a Campnosperma brevipetiolata branch

Obscured from some angles

Non-obvious even from close range.

Class opened with a slide deck on setting up GPSTest for Android. The deck also mentions iOS Compass and iOS GPS Tracks.

Scrap paper was provided so students could reference the coordinates as they walked.

iPhone compass doesn't display decimal places for the seconds. Of 14 students 12 students had iPhones. Compass doesn't display decimal places for arcseconds. Note that one iPhone had a Compass app that looked different and displayed decimal degrees. The phone appeared to be an older phone. One student found that GPS Tracks would report two decimal places for arcseconds. 

Franson would locate Sha Sha. Both Franson and Mitchy were working with Compass on an iPhone. This put them within ten to fifteen meters of Sha Sha, but no closer. 

Maylanica, Ivy Faye, and Leila'Ona had followed Franson and Mitchy, with Austin further back following them. Only Franson and Mitchy were navigating. Mitchy and Franson had initially entered the coordinates into Apple Maps, which gave them the location of Sha Sha. They did not seem to know how to orient the map to help them get close to Sha Sha, although the app did get them to the student center. I do not want this exercise to become "use a map app" to find Binky/Sha Sha, but at the same time I cannot hope to constrain the choices the students make. The intent, however, is discovery learning about latitude and longitude. 

With 12 of the 14 students on an iPhone and Compass being the dominant app, the lab was switched up to determine the number of meters per arcsecond.

The intent was to start at E 158° 09' 30" and walk to E 158° 09' 40' along latitude N 6° 54' 34' or possibly N 6° 54' 44". Clearing a culvert on Romantic Drive seems to the former, and the latter is necessary to clear a drainage ditch near the bookstore. But the latter may actually clip the health center. 

Start was as captured above, near the bookstore. 

Looking south from the start point. No photos were captured on this run: this was the first time the new measuring wheel was used. The wheel was a massive improvement: measurements to a tenth of a meter, and the wheel can roll backward winding down the distance measurement. The walk was significantly longer. Each student flipped a second at a different place. With the Compass users flipping a second 15 meters ahead of the GPSTest and GPS Tracks user. This was because Compass flips to 31 arcseconds at 30.5 arcseconds. This was certainly problematic in the field. This meant making multiple stops to read distances for each student. This also generated unique distance values - a plus. 

The existence of GPS Tracks on iOS should allow the class to get back to arcminutes. Or to get decimal arcseconds. Arcseconds proved interesting: There are just over 30 meters per arcsecond here at 6° 54'. That makes it easy to calculate meters per arcminute, sixty arcseconds in an arcminute. 

Prior to going out on the lawn the class was briefed on the layout of the laboratory.

The data table based on GPSTest data gathered by the author. Controlling the distance in meters is far easier than controlling the distance in arcminutes.

The data was ferociously linear. 

With a slope of 31.96364 meters per arcsecond, and a potential resolution of 0.01 arcseconds, GPSTest and GPS Tracks can put one - theoretically only - within 32 centimeters of a location. Of course there are other error issues to consider. But theoretically accuracy to within a British foot is possible. Putting a searcher right on top of Sha Sha. 

Arcseconds worked better than expected, the data gathering process was lengthy. The weather cooperated beautifully this term. Arcminutes became the default because the earliest GPS units displayed in this format by default. Perhaps shifting to seconds is preferable? That or decimal degrees? But decimal degrees would require returned to fixed distances in meters which would be less intuitively obvious than the approach of walking a single arcsecond and then taking a reading. The complication with arcseconds is that one inevitably has to record the decimal places: the GPS reading is not stable enough to land on ".00" - see the data table above. One then has to record the decimal points. In the sun. On a cell phone. Solve the data gathering complications and arcseconds are the way to go.