TY - JOUR AU - Witting, Lars AU - Pike, Daniel G PY - 2009/09/01 Y2 - 2024/03/28 TI - Distance estimation experiment for aerial minke whale surveys JF - NAMMCO Scientific Publications JA - NAMMCOSP VL - 7 IS - 0 SE - Articles DO - 10.7557/3.2709 UR - https://septentrio.uit.no/index.php/NAMMCOSP/article/view/2709 SP - 111-116 AB - <div>A comparative study between aerial cue&ndash;counting and digital photography surveys for minke whales conducted in Faxafl&oacute;i Bay in September 2003 is used to check the perpendicular distances estimated by the cue-counting observers. The study involved 2 aircraft with the photo plane at 1,700 feet flying above the cue&ndash;counting plane at 750 feet. The observer&ndash;based distance estimates were calculated from head angles estimated by angle-boards and declination angles estimated by declinometers. These distances were checked against image&ndash;based estimates of the perpendicular distance to the same whale. The 2 independent distance estimates were obtained for 21 sightings of minke whale, and there was a good agreement between the 2 types of estimates. The relative absolute deviations between the 2 estimates were on average 23% (se: 6%), with the errors in the observer&ndash;based distance estimates resembling that of a log-normal distribution. The linear regression of the observer&ndash;based estimates (<em>obs</em>) on the image&ndash;based estimates (<em>img</em>) was <em>Obs</em>=1.1<em>Img</em> (R2=0.85) with an intercept fixed at zero. There was no evidence of a distance estimation bias that could generate a positive bias in the absolute abundance estimated by cue&ndash;counting.</div> ER -