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.

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