Thursday, February 23, 2017

Converting arcminutes and decimal degrees to meters

In the morning section I began out on the lawn, foregoing the usual introduction in the classroom. I had given a brief introduction to latitude and longitude on Monday. Wednesday the hide and seek went well, only one group failed to find the rendezvous point. The hide was sufficiently cloaked that the lead seekers had to bring home the last digit on the GPS unit to find me. And that led naturally to the question: just how far is 0.001 arcminutes? This leads to a focus in the Thursday laboratory on determining the conversion from meters to arcminutes. I opted not to start in the classroom on Thursday but to launch from the field. This works well if Monday and Wednesday have laid down the basic concepts.


Regina, Anjannet, Mandylae, Tristan, Sasha being blinded by the low morning sun

The 8:00 section ran east along North 6° 54.568" The Garmin Vista was still set in decimal degrees, so Anjannet started at N 6.90945°.


The group headed east, Anjannet, Mayleen, and Sasha in the second row.

Tristan, Dee-L, Sasha, Mayleen on the far right

Mandylae on the surveyor's wheel 


Heading east, Maygen second from the right

A modified conversion sheet provided data at one meter increments out beyond 180 meters. This is where the road passes campus. At just over 180 meters one crosses the 0.100 arcminute mark.



About 1860 meters per minute.


Anjannet's GPS was still set to decimal minutes. About 111,460 meters per degree or thereabouts. Using Desmos requires manually adjusting both the x and y axis to properly display the data.


In the afternoon I wanted to try to run north into the new soccer field. I did not want to start too far east and hit the cliff, or too far west and wind up in the bush to the west of the field.


I opted to start at the LRC, but this was somewhat problematic.  The start was at N 06° 54.530 on some GPS units, 0.531, 0.532, 0.527, and 0.528 on other units. The LRC blocked reception and limited accuracy.

The LRC is simply a suboptimal start and a better path than east 158° 09.586 ought to be explored. The class veered consistently right of north.


The track is not a bad track per se, longer that the traditional east track, which surprised me. The ".530" start is harder mathematically, and that was complicated by the multiple different start values that had to be subtracted. I chose to subtract these in the field rather than the lab so students could "see" where the values in the table were coming from. Ultimately the sun was scorching hot and that actually made thinking harder for everyone.


The view from the starting point.

Jeremiah on the surveyor's wheel, Aimina checks her longitude

Saleen and Vanessa

Vanessa, standing in the view of the path back uproute

The uproute line

Crossing the road

180 meters was just across the road.

Thus 210 meters is possible, 30 more than is possible on the east route.

Headed for 210, and 240 is theoretically possible.


Pelida remained true to 158° 09.586' and was well west of the group

Kimsky taking notes, everyone else reading their GPS


Pelida's data and graph, 1950 meters per arcminute on the polar route.

Wednesday, February 22, 2017

Hide and seek discovery learning

Navigating purely by latitude and longitude coordinates was again taught as a discovery learning exercise where I hid in the back bush and the students tried to find me using a GPS and my coordinates.


On Monday I preselected my hide. One student had downloaded a GPS app to their phone that used decimal degrees, so I included the decimal degrees coordinates this year.


The arcminute display.

The hid was a hollow in the side of a hill with embankments to the east and north.


Hard to see the hide from across the valley.


The view from the hide.


First arrivals were Jeremiah and Kimsky, both of whom had to come right on top of my position in the hide. A large group traipsed along behind them. One of the seven GPS units failed last term. A sixth one failed back at the office today. Only five GPS units were available.


Jayvin, Dorothy, and Tedrick were following closest behind Jeremiah and Kimsky.


Vanessa, Kiana, and Jayvin.


Kiana, Jayvin, and Jeremiah


Iva Nicole arrives.

Jeremiah and Dorothy wait.


Mayleen arrives.
 Tristan appears.



This term the group chose to hunker down and wait. They said there were others up at the road, while one group had headed towards the gym.


With voices being heard, Vanessa and Aimina wait at the hide.


Upslope others wait, the group had fallen quiet.


Tristan took up a sniper's nest position. We could hear Sasha from across the valley.


Pelida was in with the main group.


As Sasha's voice rang out across the fields, the group chose to hunker down further, crouching behind the tall grass.

The source of the whoops and loud calls appeared.  Sasha suddenly saw the large group up in the hollow.


Sasha followed by Anjannet.


Sasha arrives, excited to find the rest of the class.

Saturday, February 18, 2017

Temperature sensing walk

Although Friday in physical science is often reserved for assessments of learning, I am always open to try something else. The division had recently acquired a remote surface temperature sensing device. Friday being a sunny day and the class meeting at noon, I thought there might be a chance to reinforce the sensation of different Celsius temperatures. The weather station here still reports in Fahrenheit, thus there is no sense of what a particular Celsius temperature means, what is hot, what is cold.

Pelida measures the top of a transformer in the midday sun

On Wednesday I had demonstrated a 0° Celsius ice water bath, 100°C boiling water, 21°C melting coconut oil, 37°C human body temperature (an oral temperature of 34°C to 35°C actually), and indoor room temperature of 28°C.

Tristan measures the cooling fin temperatures as Tiffany, Pelida, Jeremiah, and Dannia look on.

Outdoors in the shade leaves and grass on the ground in the shade were registering 33°C on Friday. The highest temperatures seen were for asphalt which repeatedly came in with peak temperatures of 55°C and 56°C. Little wonder running on the road is challenging here: air temperatures above the road can be significantly elevated above ambient temperatures.

Vanessa measures water surface temperature. 

Water and wet surfaces consistently came in a few degrees Celsius lower than the 32°C to 33°C we were seeing for non-sunny surfaces. Cars were checked, with black cars coming in around 45°C and white cars roughly ten degrees Celsius cooler. Black t-shirts were hotter than white t-shirts. The tops of heads were also checked, with one student showing significantly hotter hair than others in the class. Someone hypothesized that coconut oil might be responsible.

I was pleasantly surprised at the interest the students showed in measuring everything around them. For homework I had them report the temperatures of the objects we measured during the class period in a follow-on homework assignment.