Homogeneous reprocessing of GPS,GLONASS and SLR observations

The International GNSS Service (IGS) provides operational products for the GPS and GLONASS constellation. Homogeneously processed time series of parameters from the IGS are only available for GPS. Reprocessed GLONASS series are provided only by individual Analysis Centers (i. e. CODE and ESA), making it difficult to fully include the GLONASS system into a rigorous GNSS analysis. In view of the increasing number of active GLONASS satellites and a steadily growing number of GPS+GLONASS-tracking stations available over the past few years, Technische Universität Dresden, Technische Universität München, Universität Bern and Eidgenössische Technische Hochschule Zürich performed a combined reprocessing of GPS and GLONASS observations. Also, SLR observations to GPS and GLONASS are included in this reprocessing effort. Here, we show only SLR results from a GNSS orbit validation. In total, 18 years of data (1994–2011) have been processed from altogether 340 GNSS and 70 SLR stations. The use of GLONASS observations in addition to GPS has no impact on the estimated linear terrestrial reference frame parameters. However, daily station positions show an RMS reduction of 0.3 mm on average for the height component when additional GLONASS observations can be used for the time series determination. Analyzing satellite orbit overlaps, the rigorous combination of GPS and GLONASS neither improves nor degrades the GPS orbit precision. For GLONASS, however, the quality of the microwave-derived GLONASS orbits improves due to the combination. These findings are confirmed using independent SLR observations for a GNSS orbit validation. In comparison to previous studies, mean SLR biases for satellites GPS-35 and GPS-36 could be reduced in magnitude from \(-35\) and \(-38\)  mm to \(-12\) and \(-13\)  mm, respectively. Our results show that remaining SLR biases depend on the satellite type and the use of coated or uncoated retro-reflectors. For Earth rotation parameters, the increasing number of GLONASS satellites and tracking stations over the past few years leads to differences between GPS-only and GPS+GLONASS combined solutions which are most pronounced in the pole rate estimates with maximum 0.2 mas/day in magnitude. At the same time, the difference between GLONASS-only and combined solutions decreases. Derived GNSS orbits are used to estimate combined GPS+GLONASS satellite clocks, with first results presented in this paper. Phase observation residuals from a precise point positioning are at the level of 2 mm and particularly reveal poorly modeled yaw maneuver periods.     

Time‐geographic Derivation of Feasible Co‐presence Opportunities from Network‐constrained Episodic Movement Data

Certain datasets on moving objects are episodic in nature – that is, the data is characterized by time gaps during which the position of the object is unknown. In this article, a model is developed to study the sparsely sampled network‐constrained movement of several objects by calculating both potential and feasible (i.e. more likely) co‐presence opportunities over time. The approach is applied to the context of a static sensor network, where the location of an object is only registered when passing a sensor location along a road network. Feasibility is incorporated based on the deviation from the shortest path. As an illustration, the model is applied to a large Bluetooth tracking dataset gathered at a mass event. The model output consists of maps showing the temporal evolution of the distribution of feasible co‐presence opportunities of tracked visitors over the network (i.e. the number of visitors that could have been present together). We demonstrate the model's usefulness in studying the movement and distribution of a crowd over a study area with relatively few sampling locations. Finally, we discuss the results with a special emphasis on the distinction between feasible and actual presence, the need for further validation and calibration, and the performance of the implementation.     

Revising the ‘host country standard’ principle: a step for China to align its overseas investment with the Paris Agreement

ABSTRACT

China’s overseas investment flows (US$ 183 billion) and stock (US$ 4.7 trillion) reached a record peak in 2016, second only to those of the US. A major cause for concern lies in the environmental sustainability of China’s overseas investment portfolio, which is compounded by the lack of transparency of China’s main development finance arms. We intend in this paper to give an update on the magnitude of green finance in China’s overseas investment and development finance portfolio on the basis of the best available estimates, and to put these figures into a broader perspective of multilateral development banks’ commitments and practices to combat climate change. We derive practical policy recommendations that Chinese development banks could take to further align China’s overseas investment with the 2°C target of the Paris Agreement, with the first step being to revise the ‘host country standard’ principle, to ensure that Chinese development banks use the most stringent of the two environmental standards, abroad or at home.

Key policy insights

• Chinese development banks lend, give or invest between US$ 38 billion and US$ 45 billion every year to developing countries, without either elaborating on, or integrating, the provisions of the Paris Agreement into their investment strategy.

• Regulations and safeguards are much more stringent for China’s domestic investment than for China’s overseas investment, and this stringency gap has been widening over recent years.

• As a step towards aligning Chinese overseas investment with the Paris Agreement, Chinese development banks could revise the ‘host country standard principle’. They could instead choose the highest among the two – recipient country or Chinese domestic – in terms of environmental stringency, consequently harmonizing overseas environmental regulation and safeguards with those that apply domestically.