Combination of geodetic observations and models for glacial isostatic adjustment fields in Fennoscandia

We demonstrate a new technique for using geodetic data to update a priori predictions for Glacial Isostatic Adjustment (GIA) in the Fennoscandia region. Global Positioning System (GPS), tide gauge, and Gravity Recovery and Climate Experiment (GRACE) gravity rates are assimilated into our model. The technique allows us to investigate the individual contributions from these data sets to the output GIA model in a self-consistent manner. Another benefit of the technique is that we are able to estimate uncertainties for the output model. These are reduced with each data set assimilated. Any uncertainties in the GPS reference frame are absorbed by reference frame adjustments that are estimated as part of the assimilation. Our updated model shows a spatial pattern and magnitude of peak uplift that is consistent with previous models, but our location of peak uplift is slightly to the east of many of these. We also simultaneously estimate a spatially averaged rate of local sea level rise. This regional rate (similar to 1.5 mm/yr) is consistent for all solutions, regardless of which data sets are assimilated or the magnitude of a priori GPS reference frame constraints. However, this is only the case if a uniform regional gravity rate, probably representing errors in, or unmodeled contributions to, the low-degree harmonic terms from GRACE, is also estimated for the assimilated GRACE data. Our estimated sea level rate is consistent with estimates obtained using a more traditional approach of direct "correction" using collocated GPS and tide gauge site

The natural resources of Morro Bay

The primary purpose of this report, then, is to document the natural resources of Morro Bay and their values; point out significant problems regarding their use and to make recommendations for preservation of these resources to planners, administrators and interested citizens. A secondary purpose of this report is to pull together into one source, all data and references on the biological resources of Morro Bay. Up to now these data have been widely distributed amongst letters, reports, papers, etc., to which few have access. At the request of Senate Resolution No. 176, 1966 First Extraordinary Session, the Department completed in December, 1966 a report entitled, "Report of the Natural Resources of Morro Bay and Proposal for Comprehensive Area Plan." Based largely upon the recommendations of that report, the San Luis Obispo County Board of Supervisors appointed a task force to prepare a comprehensive area plan for the Morro Bay area and its watershed. Hence, the information herein is presented in order that the natural resources of Morro Bay will be given adequate consideration, based on the best data available, in the proposed comprehensive area plan and in other plans such as one being prepared by the Coastal Zone Conservation Commission. (148ppp.

Geometry-based TCAR models and performance analysis

Abstract. The paper presents a methodology that combines geometry-based models and geometric constraints for improved three carrier ambiguity resolution (TCAR). First of all, a general modelling strategy using three or more phase-based ranging signals is presented. The strategy can generally identify three best “virtual ” signals to allow for more reliable AR under certain observational conditions characterised by ionospheric and tropospheric delay variability, level of phase noise and orbit accuracy. The selected virtual signals often have minimum or comparatively low ionospheric effects, and thus are known as ionosphere-reduced virtual signals. As a result, the ionospheric parameters in the geometry-based observation models can be eliminated for long baselines, typically those of length tens to hundreds of kilometres. Secondly, the general formulation of the equation system for the ambiguity resolution problem is examined. This general formulation enables the combination of apriori position and ambiguity and ionosphere information, to achieve reliable integer solutions or high availability of Real-Time Kinematic (RTK) solutions. Thirdly, numerical experiments have been performed and three sets of dual-frequency GPS data have been collected over baselines of length 21km, 56km and 74km and the performance benefits of the proposed algorithms have been investigated. Results confirm that the AR with the ionosphere-reduced NL signals, instead of the original L1 and L2 signals, performs better over longer baselines. For instance, the AR success rate for the 74km data set is improved from 88 % to 93%. Introducing geometric constraints, particularly, apriori position and ionospheric corrections predicted from the previous epochs, AR reliability is further improved, to 98 % for the above data set