10.1371/journal.pone.0126292.g001 Vsevolod Afanasyev Vsevolod Afanasyev Sergey V. Buldyrev Sergey V. Buldyrev Michael J. Dunn Michael J. Dunn Jeremy Robst Jeremy Robst Mark Preston Mark Preston Steve F. Bremner Steve F. Bremner Dirk R. Briggs Dirk R. Briggs Ruth Brown Ruth Brown Stacey Adlard Stacey Adlard Helen J. Peat Helen J. Peat Vertical component of the velocity of the centre of gravity of the penguin. Public Library of Science 2015 operator requirements Passive radio frequency tags penguin crossings operation costs design specification Travel Direction rfid Reliable discrimination weighbridge weather conditions Macaroni penguins Radio Frequency Identification System system description penguin weight researcher processing options Eudyptes chrysolophus 24 hours South Georgia New Design Radio Frequency Identification data trip direction Low unit Bird Island 2015-04-20 03:19:56 Figure https://plos.figshare.com/articles/figure/_Vertical_component_of_the_velocity_of_the_centre_of_gravity_of_the_penguin_/1385898 <p>The figure shows the vertical component of the velocity of the centre of gravity of the penguin <i>v</i>(<i>t</i>), calculated using the first approximation (6). Any velocity trend (slope) indicates the weight estimate is in error. The slope of the linear regression (also shown) gives the relative error of the first approximation (8). Thus we calculate the second approximation of the penguin weight (10).</p>