On the other hand, depending on the mapping function and zenith total delay in the tropospheric correction, the planar model with tropospheric correction can provide decimeter level accuracy for low altitude stations. If decimeter level accuracy for water surface fluctuation is required, the planar model cannot be used when a receiver is at an altitude of a few hundred meters and observations are taken at low elevation angles. This paper evaluates three models: the planar model, the planar model with tropospheric correction and a model based on. One important step to utilize this technique is modeling the interferometric path (the difference between the direct and the reflected signal paths). Read moreĪltimetry by using GNSS (Global Navigation Satellite Systems) reflectometry is regarded as a new promising technique. For example, for 5-meter reflector height, observations below 20° elevation angle have more than 1-centimeter atmospheric altimetry error. Lastly, we present the limiting conditions for negligible atmospheric altimetry correction (sub-cm), over domain of satellite elevation angle and reflector height. We also provide an equivalent correction for the effective satellite elevation angle such that the refraction effect is nullified. We define the interferometric slant factor used to map interferometric zenithal delays to individual satellites. About half of the delay was found to originate above the receiving antenna at low satellite elevation angles. Assessment results showed excellent agreement for the angular component and good for the linear one. We provide specific expressions for the linear and angular components of the atmospheric interferometric delay and corresponding altimetry correction, parameterized in terms of refractivity and bending angle. ground-based GNSS-R and validated them against raytracing. We have developed closed-form expressions for atmospheric refraction in. Although atmospheric delays are best investigated via ray-tracing, its modification for reflections is not trivial. Radio waves used in Global Navigation Satellite System Reflectometry (GNSS-R) are subject to atmospheric refraction, even for ground-based tracking stations in applications such as coastal sea-level altimetry. With fewer approximations than the previous approach (directly using the mapping function), the new delay error model is also more accurate but with less absolute improvement of about 3 % compared to the previously existing model. For the GNSS-IR atmospheric delay, we revise the geometry of the GNSS signal path for the case of coastal GNSS-IR where the antenna is within 98 % of the atmospheric bending effect, compared to about 88 % with the previously adopted approach. For the bending effect, we propose a new calculation which takes into account the water vapour content and utilizes the widely used mapping function approach to account for the elevation dependence. Also, usually very low elevation angle observations are used in GNSS-IR, which makes the atmospheric impact even more important. Unlike GNSS positioning applications, in GNSS-IR the bending effect is as important as the delay effect. We revise the tropospheric error model in ground-based GNSS-IR for sea level applications.
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