// Data for the Infinite Corridor at MIT
// for prediction of event known as "MIThenge"
//
// More info at also http://web.mit.edu/planning/www/mithenge.html
// Thanks to Keith Winstein and Ken Olum for various data.
//
// This file contains the coordinates of the corridor and is used by
// the programs mithengesun.frink and mithengemoon.frink
//
// For worked predictions, see https://futureboy.us/mithenge/
//
// Alan Eliasen, eliasen@mindspring.com

North = +1
South = -1
West = +1
East = -1

// Figures from Keith Winstein, GPS-surveyed for east side of corridor
// which is the observation point.
lat = 42.36002 degrees North
long = 71.09332 degrees West

// Surveyed property line for MIT.  The Infinite Corridor *should*
// be about parallel to this line, but that may not be exactly right.
//
// corridorAzimuth = 245.47391075 degrees

// Azimuth of corridor as surveyed via GPS by Alan Eliasen and
// Matthias Huerlemann, December 2004.  There is some uncertainty in this
// measurement, but it's an average of a large number of differential GPS
// readings (GPS + WAAS) for lines extended from the east and west sides of
// the corridor, about 446 meters apart.
// 
//    This reading also better matches "anomalous" historical observations
// such as the 2-2-1998 picture by Paul Schechter,
// http://web.mit.edu/planning/www/mithenge-schechter.jpg
// corridorAzimuth = 246.243152 degrees

// Corridor azimuth based on average of 2 observations by Ken Olum on
// 2005-01-31 
// corridorAzimuth = 245.84 degrees

// Corridor azimuth based on average of 2 observations by Ken Olum and
// 6 GPS measurements by Lenny Foner
// corridorAzimuth = 245.693 degrees

// Revised corridor azimuth based on more measurements by Lenny Foner
// corridorAzimuth = 245.737 degrees

// Value from Jim Leonard's IMG5145, 
// See mithengereverse3.frink
// corridorAzimuth = 245.587 degrees

// 2019 figures from mithengereverse8.frink plus Ken Olum's figures:
// corridorAzimuth = 245.715 degrees

corridorAzimuth = 245.75 degrees

// Conversion to coordinate system used by Meeus
corridorAzimuthMeeus = (corridorAzimuth - 180 degrees) mod circle

corridorLength = 251 m
doorHeight = 13 ft

// The doorway near the Massachusetts Avenue (west) end of the Infinite
// corridor on the 3rd floor is only about 5 feet wide.
doorWidth = 9 ft

// The following angle may be added to or subtracted from the azimuth of the
// centerline of the corridor and indicates the extreme azimuth angles that
// are visible from the back of the corridor and viewing from either the
// far left or far right side of the corridor.  It's equal to about
// 0.62 degrees.
azimuthCorrection = arctan[doorWidth, corridorLength]

// Temperature and pressure for refraction calculations.
pressure = 996 millibars