scholarly journals CryoSat-2 interferometric mode calibration and validation: A case study from the Austfonna ice cap, Svalbard

2022 ◽  
Vol 269 ◽  
pp. 112805
Author(s):  
Ashley Morris ◽  
Geir Moholdt ◽  
Laurence Gray ◽  
Thomas Vikhamar Schuler ◽  
Trond Eiken
Keyword(s):  
Calibration And Validation ◽  
Ice Cap

Calibration and Validation of Microscopic Traffic Simulation Tools: Stockholm Case Study

2003 ◽  
Vol 1831 (1) ◽  
pp. 65-75 ◽  
Author(s):  
Tomer Toledo ◽  
Haris N. Koutsopoulos ◽  
Angus Davol ◽  
Moshe E. Ben-Akiva ◽  
Wilco Burghout ◽  
...  
Keyword(s):  
Travel Behavior ◽  
Traffic Simulation ◽  
Choice Model ◽  
Aggregate Data ◽  
Flow Measurements ◽  
Microscopic Traffic Simulation ◽  
Calibration And Validation ◽  
The North ◽  
Sensor Locations

The calibration and validation approach and results from a case study applying the microscopic traffic simulation tool MITSIMLab to a mixed urban-freeway network in the Brunnsviken area in the north of Stockholm, Sweden, under congested traffic conditions are described. Two important components of the simulator were calibrated: driving behavior models and travel behavior components, including origin–destination flows and the route choice model. In the absence of detailed data, only aggregate data (i.e., speed and flow measurements at sensor locations) were available for calibration. Aggregate calibration uses simulation output, which is a result of the interaction among all components of the simulator. Therefore, it is, in general, impossible to identify the effect of individual models on traffic flow when using aggregate data. The calibration approach used takes these interactions into account by iteratively calibrating the different components to minimize the deviation between observed and simulated measurements. The calibrated MITSIMLab model was validated by comparing observed and simulated measurements: traffic flows at sensor locations, point-to-point travel times, and queue lengths. A second set of measurements, taken a year after the ones used for calibration, was used at this stage. Results of the validation are presented. Practical difficulties and limitations that may arise with application of the calibration and validation approach are discussed.

Using Automatic Calibration with Microscopic Traffic Simulation

2008 ◽  
Vol 12 (2) ◽  
pp. 106-110
Author(s):  
Iisakki Kosonen ◽  
Keyword(s):  
Error Function ◽  
Simulation Models ◽  
Automatic Calibration ◽  
Microscopic Simulation ◽  
Detailed Model ◽  
Microscopic Traffic Simulation ◽  
Calibration And Validation ◽  
University Of Technology ◽  
Detailed Simulation

The microscopic simulation is getting increasingly common in traffic planning and research because of the detailed analysis it can provide. The drawback of this development is that the calibration and validation of such a detailed simulation model can be very tedious. This paper summarizes the research on automatic calibration of a high-fidelity micro-simulation (HUTSIM) at the Helsinki University of Technology (TKK). In this research we used ramp operation as the case study. The automatic calibration of a detailed model requires a systematic approach. A key issue is the error-function, which provides a numeric value to the distance between simulated and measured results. Here we define the distance as combination of three distributions namely the speed distribution, gap distribution and lane distribution. We developed an automated environment that handles all the necessary operations. The system organizes the files, executes the simulations, evaluates the error and generates new parameter combinations. For searching of the parameter space we used a genetic algorithm (GA). The overall results of the research were good demonstrating the potential of using automatic processes in both calibration and validation of simulation models.

scholarly journals Hydrodynamic Modeling of a Tropical Tidal River Using the Dynamic Estuary Model (DYNHYD5): A Case Study in Sibu Laut River, Sarawak, Malaysia

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Chen-Lin Soo ◽  
Teck-Yee Ling ◽  
Lee Nyanti
Keyword(s):  
Field Data ◽  
Model Simulation ◽  
Simulated Data ◽  
Hydrodynamic Modeling ◽  
Tidal River ◽  
Water Quality Simulation ◽  
Calibration And Validation ◽  
Simulated Flow ◽  
Good Agreement

Application of the Dynamic Estuary Model (DYNHYD5) in a tropical tidal river is limited. The successfully calibrated and validated hydrodynamic model is valuable in subsequent water quality simulation for environmental management. Hence, a hydrodynamic modeling approach using the DYNHYD5 was conducted in a tropical tidal river in Malaysia. Samplings were conducted in the Sibu Laut River to collect the hydrology data for model simulation. The model was calibrated and validated by comparing the simulated flow and mean depth with the field data at different simulation periods of time. The results showed that the model DYNHYD5 was successfully calibrated with channel flows and mean depths and then reproduced with good agreement in validation. The observed and simulated data were linearly correlated (R2 > 0.8) with values of slope γ ranging from 0.891 to 1.204 in both calibration and validation. The Nash–Sutcliffe coefficient of efficiency (NSE) of more than 0.7 in both calibration and validation also indicated satisfactory comparison between the observed and simulated data. The result indicated that the application of the DYNHYD5 is feasible in a tropical tidal river in Malaysia.

scholarly journals Simulation, calibration and validation protocols for the model 3D-CMCC-CNR-FEM: a case study in the Bonis’ watershed (Calabria, Italy)

2017 ◽  
Vol 14 (4) ◽  
pp. 247-256 ◽  
Author(s):  
A Collalti ◽  
C Biondo ◽  
G Buttafuoco ◽  
M Maesano ◽  
T Caloiero ◽  
...  
Keyword(s):  
Calibration And Validation

scholarly journals Multi-scale Calibration and Validation of MHYDAS-Erosion for A Small Mediterranean Vineyard Catchment: A Case Study

2014 ◽  
Vol 27 (1) ◽  
pp. 21-36
Author(s):  
Silvio Jose Gumiere ◽  
Laurence Delattre ◽  
Yves Le Bissonnais ◽  
Bruno Cheviron ◽  
Abir Ben Slimane ◽  
...  
Keyword(s):  
Soil Loss ◽  
Expert Knowledge ◽  
Physical Parameters ◽  
Calibration And Validation ◽  
Multi Scale ◽  
Spatially Distributed ◽  
Scale Calibration ◽  
Parameter Values ◽  
Total Discharge

Abstract In this work we present a case study of the multi-scale calibration and validation of MHYDAS-Erosion applied to a Mediterranean vineyard. The calibration was performed using expert knowledge in linking physical parameters to land uses with the automatic parameter estimation software PEST. MHYDAS-Erosion was calibrated and validated using spatially distributed observations on total discharge and soil loss. Calibration has been performed within six rainfall events; both hydrological and erosion parameters were calibrated using RMSE, R2 and the modified version of the Nash-Sutcliffe model efficiency criteria. Calibration results indicate there was good agreement between simulated and observed total discharge and total soil loss at the seven observation points (modified Nash-Sutcliffe efficiency (mNSE) ranging between 0.89 and 0.95). Acceptable results were obtained in terms of parameter values, identification of their physical meaning and coherence. However, some limitations were also identified, and could be remedied in more detailed studies involving (i) spatially-distributed rainfall on the catchment, (ii) a description of groundwater exfiltration and (iii) spatially-distributed properties of the ditches over the catchment. Validation results were quite satisfactory for three of the four validation events. The results from this case study suggest that MHYDAS-Erosion may need a specific calibration when applied to another catchment, but once it is calibrated, it could be used for multi-scale soil loss forecasting.

scholarly journals Volcano–glacier interactions on composite cones and lahar generation: Nevado del Ruiz, Colombia, case study

2007 ◽  
Vol 45 ◽  
pp. 115-127 ◽  
Author(s):  
J.C. Thouret ◽  
J. Ramírez C. ◽  
B. Gibert-Malengreau ◽  
C.A. Vargas ◽  
J.L. Naranjo ◽  
...  
Keyword(s):  
Pyroclastic Flows ◽  
Pyroclastic Density Currents ◽  
Density Currents ◽  
Long Term Effects ◽  
Ice Cap ◽  
The North ◽  
Potential Source ◽  
Ice Field

AbstractThe catastrophic lahars triggered by the 13 November 1985 eruption of the ice-clad Nevado del Ruiz volcano, Colombia, demonstrate that the interaction of hot pyroclasts with snow and ice can release 30–50 millionm3 of meltwater in 30–90 minutes. The 1985 eruption caused a 16% loss in area and a 9% loss in volume of snow, firn and ice. Turbulent pyroclastic density currents mechanically mixed with snow and produced meltwater at a rate of 0.5–1.6mms–1. Laboratory experiments suggest that turbulent, fluidized pyroclastic density currents exert mechanical and thermal scour, thereby efficiently transferring heat from hot pyroclasts to snow. Ice cap loss at Nevado del Ruiz continued between 1985 and 2000, representing a ∽52% decline in area and a ∽30% fall in volume. Ice 60–190m thick caps the east and southeast summit plateau, whereas an ice field < 30m thick and devoid of snow is retreating on the north, northeast and west edges. This asymmetrical distribution of ice reflects combined long-term effects of the 1985 eruption and of the post-1985 ice cap retreat. Should volcanic activity resume, steep-sided glaciers can fail and pyroclastic flows and surges can sweep the snowpack and generate mixed avalanches and lahars. Although the potential source of meltwater has decreased since 1985, extensive debris at the ice cap margins can be incorporated to future lahars.

scholarly journals Calibration and Validation of a Shared Space Model: Case Study

2016 ◽  
Vol 2588 (1) ◽  
pp. 43-52 ◽  
Author(s):  
Bani Anvari ◽  
Michael G. H. Bell ◽  
Panagiotis Angeloudis ◽  
Washington Y. Ochieng
Keyword(s):  
Model Case ◽  
Space Model ◽  
Calibration And Validation ◽  
Shared Space

scholarly journals Digital Mapping in Polar Regions from Landsat Photographic Products: A Case Study

1986 ◽  
Vol 8 ◽  
pp. 47-50 ◽  
Author(s):  
J.A. Dowdeswell ◽  
A.P.R. Cooper
Keyword(s):  
Control Point ◽  
Image Interpretation ◽  
Production Method ◽  
Polar Regions ◽  
Landsat Images ◽  
Map Projections ◽  
Digital Mapping ◽  
Ice Cap ◽  
Ground Control Points

Landsat photographic products on the Space Oblique Mercator (SOM) projection are used to construct a map of Nordaustlandet (Svalbard), of known accuracy. The map includes ice divides. Accurately enlarged Landsat images were digitized. Combined digitizer and operator errors were 64 m, at the enlargement scale. Fifteen ground control points rixed the two scenes. RMS errors in control point identification were <123 m. Geographical coordinates were extracted by: 1) converting digitizer coordinates to SOM cartesian coordinates and 2) transforming these coordinates to latitude and longitude. This map production method is applicable to any imagery of known projection. The digitally stored map may be plotted on a variety of map projections and scales. Two problems in image interpretation were: I) shadows obscuring detail on NNE-facing coasts and 2) summer snow cover obscuring parts of the terrestrial ice cap margins, The map is similar to an east coast map produced from Landsat computer compatible tapes. Differences between the Landsat map and a 1:50 000-scale aerial photograph were <100 m.

scholarly journals Geodetic mass balance record with rigorous uncertainty estimates deduced from aerial photographs and lidar data – Case study from Drangajökull ice cap, NW Iceland

2016 ◽  
Vol 10 (1) ◽  
pp. 159-177 ◽  
Author(s):  
E. Magnússon ◽  
J. Muñoz-Cobo Belart ◽  
F. Pálsson ◽  
H. Ágústsson ◽  
P. Crochet
Keyword(s):  
High Resolution ◽  
Mass Balance ◽  
Bias Correction ◽  
Aerial Photographs ◽  
Glacier Surface ◽  
Ice Cap ◽  
Uncertainty Estimates ◽  
Lidar Dem ◽  
Geodetic Mass Balance

Abstract. In this paper we describe how recent high-resolution digital elevation models (DEMs) can be used to extract glacier surface DEMs from old aerial photographs and to evaluate the uncertainty of the mass balance record derived from the DEMs. We present a case study for Drangajökull ice cap, NW Iceland. This ice cap covered an area of 144 km2 when it was surveyed with airborne lidar in 2011. Aerial photographs spanning all or most of the ice cap are available from survey flights in 1946, 1960, 1975, 1985, 1994 and 2005. All ground control points used to constrain the orientation of the aerial photographs were obtained from the high-resolution lidar DEM. The lidar DEM was also used to estimate errors of the extracted photogrammetric DEMs in ice- and snow-free areas, at nunataks and outside the glacier margin. The derived errors of each DEM were used to constrain a spherical semivariogram model, which along with the derived errors in ice- and snow-free areas were used as inputs into 1000 sequential Gaussian simulations (SGSims). The simulations were used to estimate the possible bias in the entire glaciated part of the DEM and the 95 % confidence level of this bias. This results in bias correction varying in magnitude between 0.03 m (in 1975) and 1.66 m (in 1946) and uncertainty values between ±0.21 m (in 2005) and ±1.58 m (in 1946). Error estimation methods based on more simple proxies would typically yield 2–4 times larger error estimates. The aerial photographs used were acquired between late June and early October. An additional seasonal bias correction was therefore estimated using a degree-day model to obtain the volume change between the start of 2 glaciological years (1 October). This correction was largest for the 1960 DEM, corresponding to an average elevation change of −3.5 m or approx. three-quarters of the volume change between the 1960 and the 1975 DEMs. The total uncertainty of the derived mass balance record is dominated by uncertainty in the volume changes caused by uncertainties of the SGSim bias correction, the seasonal bias correction and the interpolation of glacier surface where data are lacking. The record shows a glacier-wide mass balance rate of Ḃ  = −0.26 ± 0.04 m w.e. a−1 for the entire study period (1946–2011). We observe significant decadal variability including periods of mass gain, peaking in 1985–1994 with Ḃ  = 0.27 ± 0.11 m w.e. a−1. There is a striking difference when Ḃ  is calculated separately for the western and eastern halves of Drangajökull, with a reduction of eastern part on average  ∼  3 times faster than the western part. Our study emphasizes the need for applying rigorous geostatistical methods for obtaining uncertainty estimates of geodetic mass balance, the importance of seasonal corrections of DEMs from glaciers with high mass turnover and the risk of extrapolating mass balance record from one glacier to another even over short distances.

scholarly journals Calibration and validation of multi-reservoir MFD models: A case study in Lyon

2020 ◽  
Vol 136 ◽  
pp. 62-86 ◽  
Author(s):  
Guilhem Mariotte ◽  
Ludovic Leclercq ◽  
S.F.A. Batista ◽  
Jean Krug ◽  
Mahendra Paipuri
Keyword(s):  
Calibration And Validation
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