“The most urgent problem facing the newly independent United States was how to pay for the war that won the country its freedom; America’s debt was enormous. Its greatest asset was the land west of the Ohio River, but for this huge territory to be sold, it had first to be surveyed—that is, measured out and mapped. And before that could be done, a uniform set of measurements had to be chosen for...

Sky models are quantitative representations of natural luminance of the sky under various atmospheric conditions. They have been used extensively in studies of architectural design for nearly a century, and more recently for rendering objects in the field of computer graphics. The objectives of this paper are to (a) describe sky models, (b) demonstrate how map designers can render terrain under...

Total Cloud Cover (TCC) retrieval from ground-based optical imagery is a problem that has been tackled by several generations of researchers. The number human-designed algorithms for the estimation TCC grows every year. However, there no considerable progress in terms quality, mostly due to lack systematic approach design algorithms, assessment their generalization ability, and quality. In this...

In this paper, an extension to the radiosity method, for the simulation of daylight, is presented. The sky hemisphere around the scene is subdivided into a set of sky patches. By defining a location on the earth, a time of day and the weather conditions (e.g., clear sky, overcast, partly cloudy) a sky model (e.g., CIE or Perez) is applied to compute the radiosity values for each sky patch. In a...

The visible and NIR maximum degree of polarization (DoP) of cloud-free skylight depends on many factors, including wavelength, sun zenith angle, surface reflectance, and aerosol properties. For clear-sky environments, radiative transfer models accurately estimate the sky DoP when each of these properties is well constrained. (The model used here was recently compared with full-sky polarization ...

An understanding of the surface albedo of high latitudes is crucial for climate change studies. MODIS albedo retrievals flagged as high quality compare well with in situ Greenland Climate Network (GC-Net) measurements but cover too little area to fully characterize Greenland's albedo in non-summer months. In contrast, poor quality MODIS retrievals provide adequate spatio-temporal coverage, but ...