Estimating the breeding population of an elephant seal colony from a single census

Our aim was to develop a method for estimating the annual number of female elephant seals pupping in a colony from a single count. This is difficult because breeding females are not synchronous so there is no time when the entire population is present. We applied models that describe arrival and departure behavior to account for those missed in any one count and calculated correction factors that yield total population from any single count throughout a season. At seven colonies in California for which we had multiple female counts per year, we found consistent timing in arrival and departure both within and between sites for as long as 50 years. This meant that the optimal correction factor, the date when the maximum number of females was onshore, was consistent. At Point Reyes, a female count on 27 or 28 Jan can be multiplied by 1.15 to yield the total female population; at Año Nuevo Island, the correction was 1.17 on 25-26 Jan; and at Año Nuevo Mainland, 1.13 on 28-30 Jan. Correction factors at Channel Island colonies and King Range were also 1.13. Across the colonies studied, the factor 1.15 multiplied by a female count between 26 and 30 Jan was close to optimal, and this provides a method for estimating the female population size at colonies not yet studied. Our method can produce population estimates with minimum expenditure of time and resources and will facilitate monitoring of the elephant seal population size over its entire range.

Characterization of Neutron Detection Systems with Confidence via Statistical Parameter Correction

Neutron detection systems utilize statistical alarm techniques where a measured false alarm rate (FAR) can vary drastically from the FAR predicted by a theoretical model. The ability to set an alarm threshold that results in a practically controlled FAR is crucial to characterize detector sensitivity with both accuracy and precision. A generalized and automated method is presented to statistically evaluate FAR performance by assuming that the FAR itself is not deterministic, but a normal stochastic process over a specific parameter to be corrected that will hereafter be referred to as the correction. In this manner, a specific correction results in not only a point estimate of FAR, but also a confidence interval. The central objective is focused exclusively on characterization assuming that experiments are executed in a tightly controlled environment so that an accurate comparison is enabled across detectors. Once a correction is calculated, the estimated FAR is only assumed accurate in a similar environment for sensitivity evaluation. Initially, the calculated correction factor was used to compare FARs across various distributions including normal, corrected normal, Poisson, and a simplified normal distribution. Later verification data sets were used to empirically demonstrate the rate of containment of measured confidence coefficients using two detectors of different technology. A second application uses the correction method to improve the signal-to-noise ratio metric to agree more with dynamic sensitivity results. Finally, a third application studies the effect of altering the duration of background acquisition on FAR performance.

COMPARISON OF GEOMETRIC CORRECTION SCHEMES FOR GEOSTATIONARY OCEAN COLOR IMAGER SLOTS WITHOUT GCPS

<p><strong>Abstract.</strong> Currently, the geometric correction process of GOCI (Geostationary Ocean Color Imager) image is performed by matching slot images against shorelines and utilizing the matching results as GCPs (Ground Control Point). However, there are several GOCI slots without shorelines and for such slots acquiring GCPs is not easy. The purpose of this paper is to compare several alternative geometric correction schemes applicable to the slots without GCPs. We analyzed three schemes. The first scheme is to apply the correction angle of the same slot in the most recent dataset. The second scheme is to apply correction angle of the previous slot in the current dataset. And the last scheme is to apply correction angle of the slot with the largest number of GCPs in the same time dataset. Overall process for comparing the quality of the three geometric correction schemes consisted of the following steps. Firstly, using ephemeris metadata of GOCI Level 1A, we established initial sensor model, which defines geometry relationship between ground coordinate system and image coordinate system of a GOCI image. And then, by matching edge detected from GOCI slot images and shoreline landmark chips, we obtained GCPs. Using these GCPs, we calculated correction angle of each slot. After then, through the three schemes, we conducted precision sensor modeling. Among three schemes, geometric correction applying the previous slot correction angle showed the best quality. The average RMSE of this scheme was about 1.4<span class="thinspace"></span>km, which was quite close to geometric correction quality applying correction angles from GCPs.</p>

Investigation of chemical composition and moisture content for different materials on the attenuation of γ rays

In the present work, materials, namely mud, sand mud, ferruginous sandstone and sandstone with different densities are used to evaluate the effect of chemical composition and moisture content on the self-attenuation coefficient factor at γ-energy range from 59.5 to 1332.5 keV. The results revealed that the attenuation coefficient increases with increasing the moisture content until the material saturate with moisture. The average value of increasing linear attenuation coefficients based on increasing moisture content are 14.3%, 16.0%, 18.2%, 28.1% and 24.8% at γ-energies 59.5, 356.0, 661.7, 1173.4 and 1332.5 keV, respectively. Chemical composition of material affected on the values of attenuation, i.e. the elements with high density have high attenuation coefficient. Significant effect of self-attenuation correction factor was observed at low γ-energies up to 500 KeV. Application of the calculated correction of environmental sample with low radioactivity content has been carried out.