An advance in geolocation by light
An advance in geolocation by light
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光地理定位的进步
DOI：
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发表时间：
2004
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通讯作者：
P. Ekstrom
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作者：
P. Ekstrom
对曙暮光的一项新分析预测，对于窄带蓝光的观测，光变曲线（辐照度与太阳仰角）在+3 °和-5°（87 °至95°天顶角）之间的形状具有特殊的刚性形状，不受云层、地平线细节、大气折射或大气尘埃负荷的显著影响。这种形状是独特的，可以在测量数据中可靠地定位，并通过模板拟合到辐照度数据为动物地理定位提供了坚实的理论基础。由此产生的方法匹配的理论模型的辐照度与时间的一天的相关部分的一天的数据，调整参数的纬度，经度和云量。在有利的情况下，只有一个参数选择将很好地拟合，并且该选择成为位置估计。整个过程可以在标签中自动进行。理论上的估计在一年的大部分时间和地球的大部分地区都有很好的准确性，只是在春分点的冬季一侧和赤道附近有困难。每当太阳穿过-5°至+3°海拔时，极地地区都是有利的，并且每当太阳大幅偏离该海拔范围时，该方法都可以产生有用的结果。基于在北纬48°陆地上采集的数据的早期结果证实了预测与季节的关系，并与早期基于阈值的方法相比显示出有希望的性能。
A new analysis of twilight predicts that for observations made in narrow-band blue light, the shape of the light curve (irradiance vs. sun elevation angle) between +3 and -5° (87 to 95° zenith angle) has a particular rigid shape not significantly affected by cloudi- ness, horizon details, atmospheric refraction or atmospheric dust loading. This shape is dis- tinctive, can be located reliably in measured data, and provides a firm theoretical basis for animal geolocation by template-fitting to irradiance data. The resulting approach matches a theoretical model of the irradiance vs. time-of-day to the relevant portion of a given day's data, adjusting parameters for latitude, longitude, and cloudiness. In favorable cases, there is only one parameter choice that will fit well, and that choice becomes the position estimate. The entire process can proceed automatically in a tag. Theoretical estimates predict good accuracy over most of the year and most of the earth, with difficulties just on the winter side of equinox and near the equator. Polar regions are favorable whenever the sun crosses -5° to +3° elevation, and the method can yield useful results whenever the sun makes a significant excursion into that elevation range. Early results based on data taken on land at 48°N latitude confirm the predictions vs. season, and show promising performance when compared with earlier threshold-based methods.