| 1. |
- Ågren, Jonas, et al.
(author)
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Improving the Swedish quasigeoid by gravity observations on the ice of Lake Vänern
- 2014
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In: International Association of Geodesy Symposia. - Cham : Springer International Publishing. - 9783319108360 ; , s. 171-177
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Conference paper (peer-reviewed)abstract
- One of the key activities in Geodesy 2010, the Swedish strategic plan for geodetic activities during the period 2011–2020, is the restoration of the gravity network and data in order to improve the accuracy of the national quasigeoid model. One weak point has been that very few gravity observations have been available over Lake Vänern, Sweden’s largest lake. During the extremely cold winters 2010 and 2011, the ice became sufficiently thick to make ice observation of gravity. The main purpose of this paper is to present the 2011 ice gravity campaign, summarise the experiences made and investigate how much the new ice observations improve the computed quasigeoid model in the area. This is investigated under the assumption that a modern Earth Gravitational Model based on GRACE and GOCE is used. It is found that new ice measurements improve the quasigeoid with a RMS of about 2–3 cm in and around the lake with a maximum improvement of 7 cm.
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| 2. |
- Hassanzadeh Siyahpoush, Morteza, 1980, et al.
(author)
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Path and speed control of a heavy vehicle for collision avoidance manoeuvres
- 2012
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In: Intelligent Vehicles Symposium (IV), 2012 IEEE. Alcalá de Henares, Spain, 3-7 June 2012. - 1931-0587. - 9781467321198 ; , s. 129-134
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Conference paper (peer-reviewed)abstract
- In an emergency situation prior to an imminent accident, first in-vehicle warning systems would intervene and aim to make the driver to take a suitable action. If the risk of accident was not eliminated, then an autonomous collision avoidance manoeuvre can prevent it. In this work, path and speed control are intended to be used to perform such a manoeuvre by using steering and braking actuators respectively. In order to provide actuators with suitable control inputs, first a path is planned for the heavy vehicle to follow during the manoeuvre. Then the path is used to calculate feedforward control inputs whereas a feedback controller assures the path tracking by compensating for errors. As a result, a robust path planning and control algorithm is designed and implemented that can perform autonomous collision avoidance manoeuvres for a heavy vehicle. Promising simulation results support ongoing works on vehicle demonstration and experiments on a real heavy vehicle.
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| 3. |
- Hill, Emma M., et al.
(author)
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Combination of geodetic observations and models for glacial isostatic adjustment fields in Fennoscandia
- 2010
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In: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 115:B07
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Journal article (peer-reviewed)abstract
- We demonstrate a new technique for using geodetic data to update a priori predictionsfor Glacial Isostatic Adjustment (GIA) in the Fennoscandia region. Global PositioningSystem (GPS), tide gauge, and Gravity Recovery and Climate Experiment (GRACE)gravity rates are assimilated into our model. The technique allows us to investigate theindividual contributions from these data sets to the output GIA model in a self‐consistentmanner. Another benefit of the technique is that we are able to estimate uncertaintiesfor the output model. These are reduced with each data set assimilated. Any uncertaintiesin the GPS reference frame are absorbed by reference frame adjustments that are estimatedas part of the assimilation. Our updated model shows a spatial pattern and magnitudeof peak uplift that is consistent with previous models, but our location of peak upliftis slightly to the east of many of these. We also simultaneously estimate a spatiallyaveraged rate of local sea level rise. This regional rate (∼1.5 mm/yr) is consistent forall solutions, regardless of which data sets are assimilated or the magnitude of a priori GPSreference frame constraints. However, this is only the case if a uniform regional gravityrate, probably representing errors in, or unmodeled contributions to, the low‐degreeharmonic terms from GRACE, is also estimated for the assimilated GRACE data. Ourestimated sea level rate is consistent with estimates obtained using a more traditionalapproach of direct “correction” using collocated GPS and tide gauge sites.
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