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This paper presents one of the most comprehensive tests conducted about the real-time kinematics (RTK) and continuously operating reference stations (CORS) network using instruments from three global positioning system (GPS) manufacturers (Leica, Topcon, and Trimble). The test was carried out between August and October 2006 in the Marmara Region of Turkey as part of the research project for establishing RTK CORS network covering all of Turkey. Three GPS networks (NET-120, NET-90, and NET-60) were designed, each consisting of six CORS points: with interstation distances of 120, 90, and 60 km, respectively. Leica, Trimble, and Topcon directly participated in the tests, each company contributing a 2 week effort. RTK surveys were compiled at check points (previously known points) and new points were generally selected in built-up areas. Flachen Korrectur parameter—Spatial correction parameters, virtual reference stations, pseudoreference stations, and master auxiliary concept techniques were used for RTK positioning. Postprocessing by network solution software was also used at check points. The results of network-based RTK and postprocessing were found to be successful at each net, the main exception being the difficulties encountered by one of the firms participating at NET-120. Results are discussed in the paper. [ABSTRACT FROM AUTHOR]

An evapotranspiration method comparison was carried out by the International Water Management Institute (IWMI, Sri Lanka), at two locations in the Gediz Basin, Turkey, in the period from May to September 1998. In the IWMI study a number of ground-based techniques were compared with results obtained by remote sensing methods. Recently, a search of the satellite active archive yielded over 70 high quality level 1b images from NOAA/AVHRR over the same time period. The processing of these images with the SEBAL algorithm enabled us to build up a detailed time series of sensible and latent heat fluxes for a period of 120 days. In this paper a comparison is made between the sensible and latent heat fluxes determined from the present series of NOAA-14/AVHRR images and the results obtained earlier from various other prediction methods applied during the 1998 IWMI project. Specifically, the NOAA/SEBAL results are assessed against the scintillometer and temperature fluctuation methods. The results show that the NOAA derived evapotranspiration values follow the seasonal irrigation cycle quite well and correspond closely to the Landsat derived values, although they are lower than the results obtained with the traditional crop factor and Penman–Monteith methods. [ABSTRACT FROM AUTHOR]