We made experiments on fundamentals of the wireless LAN positioning, including 3-demensional positioning accuracy. A typical experiment was conducted in a gymnasium with furniture emulating the office environment. The horizontal accuracy was 2.6m and the vertical was 4.4m (67%probability) at 1 to 2m height. Detection of the current floor is not possible by the wireless LAN positioning in the usual office environment. Mainfactors of the error are the multipath and the geographical arrangement of wireless LAN access points. Motion of the wireless LAN instrument, which is the positioning target, in the walking speed does not affect positioning accuracy. A microwave oven did not adversely affect the positioning accuracy in these experiments.
An operational scheme for masking cloud-contaminated pixels in Advanced Very High Resolution Radiometer (AVHRR) daytime data was developed, evaluated and presented. Dynamic thresholding was used with channel 1, 2 and 3 to automatically create a cloud mask for a single image. Then the 10-day cloud coverage imagery was generated over the whole Asian region along with cloud-free composite imagery. Finally the monthly based compiling was conducted based on the derived cloud coverage imagery in terms of land cover and country. As a result, it was found that 20-day is required to acquire the cloud free data over the whole asia using NOAA AVHRR. The 10-day cloud coverage and cloud free composite imagery derived in this research is available via the website http: //webpanda.iis.u-tokyo.ac.jp/CloudCover/.
The interest to monitor cloud properties from space- and ground-based observations is based on the large influence that clouds have on the Earth and Atmosphere energy balance. The quantitative 3D description of clouds is important for refined methods in nowcasting and the modeling of weather and climate. Multi-angle Earth Observation (EO) image data from ATSR2 (onboard ERS-2), AATSR (onboard Envisat) and MISR (onboard EOS-Terra) were used to estimate cloud-top height (CTH) . Because of the cloud advection within the time delay between the acquisition of two different viewing angles from one polar-orbiting satellite, the preliminary cloud-top heights had to be corrected by this wind induced error. This paper describes the methodology for CTH estimation from multi-view satellite sensors, including wind correction with cloud-top winds (CTW) extracted from Meteosat images. The presented case studies include validation with independent data, i.e. our new ground-based stereo camera system, ground-based radar, soundings and CTHs from other satellites and/or retrieval techniques. Finally, a case study is shown where the satellite- and ground-based 3D cloud boundary results were combined.