scholarly journals Modeling the signature of a transponder in altimeter return data and determination of the reflection surface of the ice cap near the GRIP camp, Greenland

1998 ◽  
Vol 44 (148) ◽  
pp. 625-633
Author(s):  
G. Haardenog-Pedersen ◽  
K. Keller ◽  
C. C. Tscherning ◽  
N. Gundestrup
Keyword(s):  
Global Positioning System ◽  
Propagation Delay ◽  
Radar Altimeter ◽  
Reflection Point ◽  
Ice Cap ◽  
Global Positioning ◽  
Satellite Radar ◽  
The Difference ◽  
Satellite Radar Altimetry

AbstractUsing an active transponder with the ERS-I and ERS-2 radar altimeters, the distance to the satellite was measured at a location close to the GRIP site, Greenland, at an altitude of 3.2 km. The measurement was executed while the transponder was in the “ice-tracking mode”. It includes a bias due to the propagation delay. The location of the transponder was determined using the global positioning system.The transponder signal was modeled and the distance from the altimeter to the effective reflection point of the transponder was determined. Since the transponder was located within 1 km of the ground tracks, the measurement was corrected for this offset. A correction was also done for the surface slope, resulting in the distance (plus bias) to the closest sub-satellite point on the surface of the (compact) snow.The transponder signal was then removed from the radar altimeter waveform, enabling the determination of the distance (plus bias from the altimeter to the first reflective surface within the snow. The différence between this distance and that obtained using the transponder was < 2 m. This shows that the surface which gives rise to the first return of the reflection agrees with the surface of the (compact, dry) snow at this high-altitude location. This is an important result to be used when studying ice-cap topography using satellite radar altimetry.

scholarly journals Modeling the signature of a transponder in altimeter return data and determination of the reflection surface of the ice cap near the GRIP camp, Greenland

1998 ◽  
Vol 44 (148) ◽  
pp. 625-633 ◽  
Author(s):  
G. Haardenog-Pedersen ◽  
K. Keller ◽  
C. C. Tscherning ◽  
N. Gundestrup
Keyword(s):  
Global Positioning System ◽  
Propagation Delay ◽  
Radar Altimeter ◽  
Reflection Point ◽  
Ice Cap ◽  
Global Positioning ◽  
Satellite Radar ◽  
The Difference ◽  
Satellite Radar Altimetry

Abstract Using an active transponder with the ERS-I and ERS-2 radar altimeters, the distance to the satellite was measured at a location close to the GRIP site, Greenland, at an altitude of 3.2 km. The measurement was executed while the transponder was in the “ice-tracking mode”. It includes a bias due to the propagation delay. The location of the transponder was determined using the global positioning system. The transponder signal was modeled and the distance from the altimeter to the effective reflection point of the transponder was determined. Since the transponder was located within 1 km of the ground tracks, the measurement was corrected for this offset. A correction was also done for the surface slope, resulting in the distance (plus bias) to the closest sub-satellite point on the surface of the (compact) snow. The transponder signal was then removed from the radar altimeter waveform, enabling the determination of the distance (plus bias from the altimeter to the first reflective surface within the snow. The différence between this distance and that obtained using the transponder was &lt; 2 m. This shows that the surface which gives rise to the first return of the reflection agrees with the surface of the (compact, dry) snow at this high-altitude location. This is an important result to be used when studying ice-cap topography using satellite radar altimetry.

scholarly journals Ice-divide flow at Hans Tausen Iskappe, North Greenland, from surface movement data

2001 ◽  
Vol 47 (156) ◽  
pp. 78-84 ◽  
Author(s):  
C. S. Hvidberg ◽  
K. Keller ◽  
N. Gundestrup ◽  
P. Jonsson
Keyword(s):  
Global Positioning System ◽  
Average Rate ◽  
Horizontal Velocity ◽  
Surface Strain ◽  
Surface Velocity ◽  
Strain Rates ◽  
Ice Cap ◽  
Movement Data ◽  
Global Positioning ◽  
North Greenland

AbstractSurface strain rates around the southeastern dome of Hans Tausen Iskappe in Peary Land, North Greenland (82.5° N, 27.5° W), are determined from global positioning system surveys of a strain net. Average longitudinal surface strain rate increases towards the dome, from (1.4 ± 0.2) × 10−4 a−1 at 5–10 ice thicknesses from the divide to (2.4 ± 1.0) × 10−4 a−1 within 1 ice thickness from the divide. Analysis of the data shows that the ice cap is presently building up within the strain net with an average rate of 〈∂H/∂t〉 = + 0.04 ± 0.02 m a−1. Assuming a uniform thickening, the shape factor of the horizontal velocity (the ratio between the vertically averaged horizontal velocity and the horizontal surface velocity) decreases towards the dome, from 0.9 at a distance of 10 ice thicknesses from the dome to 0.5 at the dome based on application of the continuity equation. Our results indicate that a region with anomalous flow is formed around the dome, supporting recent indications reported by Vaughan and others (1999). It is not possible from our data to constrain parameters of the flow law, because there is no independent estimate of the significant present thickening of the central part of the ice cap and its pattern around the dome.

Monitoring Players’ Readiness Using Predicted Heart-Rate Responses to Soccer Drills

2018 ◽  
Vol 13 (10) ◽  
pp. 1273-1280 ◽  
Author(s):  
Mathieu Lacome ◽  
Ben Simpson ◽  
Nick Broad ◽  
Martin Buchheit
Keyword(s):  
Heart Rate ◽  
Global Positioning System ◽  
Daily Basis ◽  
Internal Load ◽  
Individual Level ◽  
Multiple Stepwise Regression Analysis ◽  
Global Positioning ◽  
Fitness Criterion ◽  
The Difference ◽  
The Individual

Purpose: To examine the ability of multivariate models to predict the heart-rate (HR) responses to some specific training drills from various global positioning system (GPS) variables and to examine the usefulness of the difference in predicted vs actual HR responses as an index of fitness or readiness to perform. Method: All data were collected during 1 season (2016–17) with players’ soccer activity recorded using 5-Hz GPS and internal load monitored using HR. GPS and HR data were analyzed during typical small-sided games and a 4-min standardized submaximal run (12 km·h−1). A multiple stepwise regression analysis was used to identify which combinations of GPS variables showed the largest correlations with HR responses at the individual level (HRACT, 149 [46] GPS/HR pairs per player) and was further used to predict HR during individual drills (HRPRED). Then, HR predicted was compared with actual HR to compute an index of fitness or readiness to perform (HRΔ, %). The validity of HRΔ was examined while comparing changes in HRΔ with the changes in HR responses to a submaximal run (HRRUN, fitness criterion) and as a function of the different phases of the season (with fitness being expected to increase after the preseason). Results: HRPRED was very largely correlated with HRACT (r = .78 [.04]). Within-player changes in HRΔ were largely correlated with within-player changes in HRRUN (r = .66, .50–.82). HRΔ very likely decreased from July (3.1% [2.0%]) to August (0.8% [2.2%]) and most likely decreased further in September (−1.5% [2.1%]). Conclusions: HRΔ is a valid variable to monitor elite soccer players’ fitness and allows fitness monitoring on a daily basis during normal practice, decreasing the need for formal testing.

scholarly journals Precise determination of Earth's center of mass using measurements from the global positioning system

1992 ◽  
Vol 19 (14) ◽  
pp. 1487-1490 ◽  
Author(s):  
Yvonne Vigue ◽  
Stephen M. Lichten ◽  
Geoffrey Blewitt ◽  
Michael B. Heflin ◽  
Rajendra P. Malla
Keyword(s):  
Global Positioning System ◽  
Center Of Mass ◽  
Precise Determination ◽  
Positioning System ◽  
Global Positioning

Determination of global positioning system (GPS) receiver clock errors: impact on positioning accuracy

2009 ◽  
Vol 20 (7) ◽  
pp. 075105 ◽  
Author(s):  
Ta-Kang Yeh ◽  
Cheinway Hwang ◽  
Guochang Xu ◽  
Chuan-Sheng Wang ◽  
Chien-Chih Lee
Keyword(s):  
Global Positioning System ◽  
Positioning System ◽  
Gps Receiver ◽  
Positioning Accuracy ◽  
Global Positioning ◽  
Receiver Clock

scholarly journals Comparative study of accuracy of differential global positioning system (DGPS) and total station instruments

2021 ◽  
pp. 49-58
Author(s):  
Didigwu Augustus Ugonna Sunday ◽  
Ogbe David .O
Keyword(s):  
Global Positioning System ◽  
Positioning System ◽  
Total Station ◽  
The Earth ◽  
Optical Distance ◽  
Reflected Light ◽  
Global Positioning ◽  
Similar Survey ◽  
The Difference ◽  
Land Using

Total Station and Global Positioning System (GPS) are two instruments used to fix position on the earth. The total station employs electro-optical distance meter method, emitting laser beams to a target and detecting light reflected off it by measuring the deviation of the wavelength of the reflected light. Global Positioning System (GPS) is a space-based satellite for rapid position determination, its’ receiver calculates its position by precisely turning the signal sent by GPS satellite high above the earth. The study aims at the assessment of the two instruments: GPS and Total Station. To achieve this aim, two surveys were performed on the same parcel of land using the two instruments. In the first part of the survey, a closed-loop traverse was performed around a chosen parcel of land using a calibrated total station. The station determined only coordinates of points from where bearings and distances were extracted. Thereafter, DGPS equipment was then used to perform a similar survey as the total station. In this case, visible satellites were used to determine the coordinates of all the stations. The results of the two methods present the distances, bearings, and coordinates. The difference between each of the results was also analyzed. Thus the maximum average difference in distance of 5mm occurred throughout the chainage and maximum differences in the coordinate of 12mm Easting and 9mm Northing were found where there are tree covers. However, the study shows that even though the two instruments are good tools for positioning, each exhibited it’s own accuracy, efficiency, advantages and disadvantage.

Assessment of the Power Potentials of Ofu Stream for Mini Hydroelectric Development

2013 ◽  
Vol 824 ◽  
pp. 129-137
Author(s):  
R.E. Ochagwuba ◽  
Samuel O. Igbinovia
Keyword(s):  
Environmental Impact ◽  
Global Positioning System ◽  
Economic Transformation ◽  
Energy Resources ◽  
Positioning System ◽  
Hydroelectric Development ◽  
Global Positioning ◽  
Analytical Assessment ◽  
Flow Power

Analytical assessment of the water energy resources in Ofu stream segments at Ofokopi, as one of the hydrologic regions of Kogi state, Nigeria was carried out. The principal focus was on the determination of the stream segments parameters of head, flow, power potentials and Environmental Impact Assessment (EIA). Two appropriate sites in close cascade were identified namely, Ofu I and Ofu II. Garmin GPSMAP 76S global positioning system was used to determine the gross hydraulic heads which gave 11.84 m and 8.60 m respectively. Power potentials of magnitude of 330 kW and 118.8 kW and annual energy generation of 2,890.80 MWhr and 1,040.69 MWhr respectively were estimated. The results of the EIA study yield negligible impact on the locality. The estimated power being in the mini hydroelectric schemes category, the identified sites could be developed to provide electric power for socio-economic transformation of the rural area.

Sign in / Sign up

Export Citation Format

Share Document