scholarly journals Horizontal Measurement Performance of Five Mapping-Grade Global Positioning System Receiver Configurations in Several Forested Settings

2008 ◽  
Vol 23 (3) ◽  
pp. 166-171 ◽  
Author(s):  
Michael G. Wing ◽  
Aaron Eklund ◽  
Sessions John ◽  
Karsky Richard
Keyword(s):  
Real Time ◽  
Measurement Errors ◽  
Measurement Accuracy ◽  
Gps Receiver ◽  
Gps Receivers ◽  
Young Forest ◽  
Significant Difference ◽  
Time Differential ◽  
Closed Canopy ◽  
Differential Corrections

Abstract We examined the horizontal measurement performance of five mapping-grade GPS receiver configurations operating simultaneously at three measurement test sites established in open sky, young forest, and closed canopy conditions. Two of the GPS receivers had external antennas, and two receivers were configured to collect data with real-time differential corrections through the Wide Area Augmentation System (WAAS). The GPS receivers collected data using 1-, 30-, and 60-point recording intervals to test the influence of the number of point recordings on position determination. We also postprocessed all data to examine the influence of differential corrections. We found statistically significant differences in measurement accuracy between GPS receiver configurations that had an external antenna and receivers that did not. The top performer for unprocessed data collected measurements with real-time differential corrections and had average measurement errors of 0.4, 0.8, and 2.2 m, in open sky, young forest, and closed canopy conditions, respectively. The top performer for postprocessed data had average measurement errors of 0.2, 0.1, and 1.2 m, in open sky, young forest, and closed canopy conditions, respectively. The influence of number of points on measurement accuracy was observed between the 1- and 30-point intervals, with no statistically significant differences between the 30- and 60-point intervals. No statistically significant difference resulted in WAAS measurements that were postprocessed. The measurement accuracies we report are acceptable for many natural resource measurement applications. These findings encourage the use of external antennas when using GPS receivers under forest canopy. In addition, point recording intervals of 30 appear to be efficient for accurate measurements with mapping-grade GPS receivers.

scholarly journals Vertical Measurement Accuracy of Mapping-Grade Global Positioning Systems Receivers in Three Forest Settings

2008 ◽  
Vol 23 (2) ◽  
pp. 83-88 ◽  
Author(s):  
Michael G. Wing ◽  
Aaron Eklund
Keyword(s):  
Real Time ◽  
Measurement Accuracy ◽  
Gps Receiver ◽  
Gps Receivers ◽  
Positioning Systems ◽  
Young Forest ◽  
Open Canopy ◽  
Time Differential ◽  
Closed Canopy ◽  
Differential Corrections

Abstract Elevation or height differences are necessary measurements for many forest operation activities. We rigorously examined the vertical measurement performance of five mapping-grade GPS receivers in three forest settings representing open-sky,young-forest, and closed-canopy conditions. The mapping-grade GPS receivers collected data simultaneously at each of the three forest settings and had different hardware and data-collection configurations, including internal and external antennas, and real-time differential corrections. We evaluated the influence of forest setting and postprocessed differential corrections on all GPS receiver measurements, including those that were collected with real-time differential corrections. We also compared the effect of 1-, 30-, and 60-point averaging intervals on vertical measurement accuracy. We found average vertical accuracies for unprocessed GPS receiver measurements of 0.9, 1.7, and 2.8 m in the open-sky, young-forest, and closed-canopy settings, respectively. The influence of data postprocessing was inconsistent under closed canopy and resulted in average vertical GPS accuracies of 0.2, 0.4, 3.3 m in open-canopy, young-forest, and closed-canopy settings, respectively. Different point averaging intervals did not result in statistically significant differences in vertical accuracies for either unprocessed or postprocessed GPS data.

scholarly journals An Examination of Five Identical Mapping-Grade Global Positioning System Receivers in Two Forest Settings

2011 ◽  
Vol 26 (3) ◽  
pp. 119-125 ◽  
Author(s):  
Michael G. Wing ◽  
Jereme Frank
Keyword(s):  
Measurement Errors ◽  
Primary Objective ◽  
Average Error ◽  
Gps Receivers ◽  
Young Forest ◽  
Significant Difference ◽  
Secondary Objective ◽  
Satellite Signal ◽  
Sky Conditions ◽  
Identical Mapping

Abstract We collected measurements using five identical high-quality mapping-grade GPS receivers that were configured the same and collected data simultaneously in two distinctly different settings within a forest. Our primary objective was to determine whether measurement accuracies were different among the mapping-grade GPS receivers. A secondary objective was to determine whether measurement accuracies were different depending on whether receivers established their locations by taking a single 1-second measurement or by averaging 30 or 60 measurements. In the open-sky setting, where receivers had few obstructions overhead, we found that all five receivers recorded measurements with similar positional accuracies. Errors were lower when measurements were differentially corrected (postprocessed). We found an average error of 1.6 m for unprocessed data and an average error of 0.2 m for postprocessed data. Our results indicate that in open-sky conditions, all five receivers performed similarly when measurements were postprocessed. In addition, there was no significant difference in accuracy whether 1, 30, or 60 points were averaged, regardless of whether data were postprocessed. In the young-forest test course, examination of errors between receivers revealed that one receiver had significantly different errors compared with other receivers, which was likely the result of environmental influences on satellite signal strength and availability. We also found that measurement errors for all five receivers were significantly lower when measurements were postprocessed. On average, measurement errors were 5.9 m for unprocessed data and 1.4 m for postprocessed data. In analyzing individual receiver errors, no receiver had significantly different measurement errors whether 1, 30, or 60 measurements were recorded.

scholarly journals Calibration and Accuracy Determination of a Microwave Type Sensor for Measuring Grain Flow

2014 ◽  
Vol 931-932 ◽  
pp. 1592-1596
Author(s):  
Renny Eka Putri ◽  
Azmi Yahya ◽  
Nor Maria Adam ◽  
Samsuzana Abd Aziz ◽  
Tajudeen Abiodun Ishola
Keyword(s):  
Real Time ◽  
Pitch Angle ◽  
Measurement Errors ◽  
Measurement Accuracy ◽  
Evaluation Study ◽  
Flow Sensor ◽  
Roll Angle ◽  
Flow Measurements ◽  
Solid Flow ◽  
Grain Flow

Impact type grain flow sensor for crop yield monitoring is known to have problem of some thrown grain by the elevator conveyor in a combine not hitting the sensing impact plate. New technology of microwave solid flow sensor was used to solve the problem of impact-type sensor. A calibration stand with its instrumentation systems to stimulate the actual operation of the clean grain auger in a rice combine had been designed and constructed in this study for the purpose of conducting the calibration and evaluation study of the sensor. Two different solid flow sensor orientations and three different solid flow sensor extrusions were investigated in order to find the best positioning of the sensor on the chute for the measurement. Results from the conducted tests indicates that the best sensor positioning is on totally flat ground at 180o orientation and 8 cm extrusion of the chute cross section (R2=0.9400). Then, the solid flow sensor was tested at seven chute pitch angle positions (i.e-4.5o, -3.0o, -1.5o, 0o, +1.5o, + 3.0o, and +4.5 o), seven chute roll angle positions (i.e-4.5o,-3.0o, -1.5 o, 0o, +1.5o, +3.0 o, and +4.5o). Finally, accuracy tests undertaken to compare the real time measurements against the average flow measurements. ANOVA test shows that both pitch angle and roll angle positions have significant effects on the measurement accuracy of the sensor. The measurement errors increased with increasing roll angles and increasing pitch angle. Conclusively, this conducted laboratory study was able to quantify the measurement accuracy of the SWR Solid Flow sensor for real-time measurement of grain flow under a simulated laboratory rice combine test set-up.

scholarly journals Experimental study on improving the accuracy of marine gravimetry by combining moving-base gravimeters with GNSS antenna array

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Zhimin Shi ◽  
Junjian Lang ◽  
Xinghui Liang ◽  
Zhibo Zhou ◽  
Aizhi Guo ◽  
...  
Keyword(s):  
Antenna Array ◽  
Real Time ◽  
Frequency Band ◽  
Antenna Arrays ◽  
Measurement Errors ◽  
Measurement Accuracy ◽  
Tectonic Activity ◽  
Gravity Measurement ◽  
Vertical Position ◽  
Point Positioning

AbstractThe gravity field is one of the Earth’s basic physical fields. The geoid can be calculated and the tectonic activity underground can be inversed by gravity anomaly. With the development of various ship-borne gravimeters and navigation technology, including the Global Navigation Satellite System (GNSS) and Strapdown Inertial Navigation System (SINS), the precision of marine gravimetry has been significantly improved (achieve or better than 1mGal). Errors arising from calculations of the correction term have become the main source of gravity measurement errors. At present, the traditional approach is to deploy a GNSS antenna, connect the GNSS antenna to the gravimeter, record the real-time position through data acquisition software, and then use this position to calculate the gravity correction item afterward. Two errors are inevitable. (1) The GNSS antenna position error is large. The pseudorange point positioning method is generally used to obtain real-time GNSS antenna positions, and the positioning accuracy is poor compared with that of precise point positioning. (2) The position coordinates of the gravimeter contain systematic errors related to the ship’s attitude. In this paper, a joint experiment including GNSS antenna arrays and ship-borne gravimeters was designed to evaluate the measurement accuracy via repeat lines on the same ship. The experimental results show the following: (1) attitude accuracies of 0.0299° for the yaw angle, 0.0361° for the pitch angle, and 0.1671° for the roll angle can be obtained at baseline lengths of 25 and 4 m. (2) The GNSS antenna array has an obvious role in determining the point acceleration in the low-frequency band (0–0.01 Hz) and the point position and velocity in the high-frequency band (0.01–1 Hz). (3) The vertical position eccentricity causes an absolute error of 1 mGal and a relative error of $${10}^{-1}$$ 10 - 1 mGal in gravity measurements and can be corrected by the GNSS antenna array method. (4) Using a GNSS antenna array can obviously improve the measurement accuracy of an instrument with a precision equaling or exceeding 1 mGal, but cannot obviously improve that to an instrument with poor precision (2 mGal or below).

scholarly journals The Impact of Bayesian Penalized Likelihood Reconstruction Algorithm on Quantitative Accuracy of Positron Emission Tomography Volumetric Measurements

2020 ◽  
Author(s):  
Liang Chen ◽  
Dongfang Chen ◽  
Tao Huang ◽  
Cen Lou
Keyword(s):  
Positron Emission Tomography ◽  
Measurement Errors ◽  
Measurement Accuracy ◽  
Penalized Likelihood ◽  
Reconstruction Algorithm ◽  
Emission Tomography ◽  
International Electrotechnical Commission ◽  
Positron Emission ◽  
Significant Difference ◽  
The Impact

Abstract Objectives The metabolic tumor volume (MTV) of positron emission tomography/computed tomography (PET/CT) is an important index to evaluate the prognosis and the responses of treatments. The purpose of this study is to assess the impact of Bayesian Penalized Likelihood (BPL) reconstruction algorithm and segmentation methods on the accuracy of MTV via a phantom study.Methods Using the National Electrical Manufactures Association/International Electrotechnical Commission (NEMA/IEC) image quality phantom, six hot spheres and background were filled with 21.56 KBq/ml and 5.39 KBq/ml Na 18 F (a sphere to background ratio of 4: 1). Acquired images were reconstructed using BPL (β = 400) and non-BPL (Ordered subsets expectation maximization + time of flight + point spread function, OSEM+TOF+PSF) algorithms, respectively. MTVs of six spheres were delineated using maximum standardized uptake value (SUV max ) percentage threshold method and iterative adaptive method, respectively. The actual measured volumes of spheres were used as the standard for comparative analysis.Results The MTVs measurement errors in BPL were 4.96%, -3.00%, 6.18%, 5.20%, -10.00% and 18.33%, which was significantly lower than that in non-BPL ( Z = - 2.562, p = 0.009), and the measurement errors in non-BPL were 16.70%, 10.77%, 26.00%, 30.00%, 61.82% and 113.33%. The optimal percentage SUV max threshold of spheres in BPL algorithm was raged in 40% - 45%, which was not affected by the ball size. And there was no significant difference of MTVs measurement accuracy between the 42%SUV max and iterative adaptive threshold (Z = -0.48, p = 0.699). However, using the non-BPL algorithm, the measurement errors of 42%SUV max and iterative adaptive delineation methods were 16.70%, 10.77%, 26.00%, 30.00%, 61.82%, 113.33%, and -7.70%, -9.00%, -8.73%, -5.20%, -12.91%, 38.33% respectively. The MTVs measurement accuracy of iterative adaptive was significantly better than that of the 42%SUV max threshold (Z = -2.24, p = 0.026). The iterative adaptive and 42%SUV max threshold methods had excellent interobserver reliability (ICCs=1.00 for all of six spheres) for MTVs measurement.Conclusion BPL reconstruction algorithm can improve the accuracy of MTVs measurements, especially for small lesions. In the case of using non-BPL methods, the iterative adaptive delineation method should be adopted to improve the accuracy of MTVs measurements.

Pollution Measurement Accuracy Using Real Time Sensors and Wastewater Samples Analysis

1993 ◽  
Vol 28 (11-12) ◽  
pp. 67-78 ◽  
Author(s):  
G. Ruban ◽  
P. Marchandise ◽  
O. Scrivener
Keyword(s):  
Real Time ◽  
Measurement Errors ◽  
Measurement Accuracy ◽  
Field Experiments ◽  
Sampling Strategy ◽  
Random Errors ◽  
Standard Samples ◽  
Particulate Pollution ◽  
Order Of Magnitude ◽  
Pollution Measurement

This paper deals with a comparison of the pollution measurement accuracy between real time pollution sensors (especially Suspended Solids - S.S.- determination by turbidimetry) and standard samples analysis on raw wastewaters. The two methods are used in commonly favourable conditions. Considering separate measurement errors, the S.S. random errors of the two methods are in the same order of magnitude (about ± 25% for a 90% confidence interval), but sampler/analyses lead to a systematic underevaluation of about 17%. These rather high figures for the sampling/analyses method are due to the cumulation of samples compounding and preservation errors. The determination of the samples collection error when estimating pollution loads is based on a set of 12 rainfall events registered during a 5 month study on a combined sewer overflow. Due to an optimized sampling strategy, the use of a 24 bottle sampler shows an average S.S. load underevaluation of only 5%, compared with the continuous estimation of the pollution sensor considered as a reference. Real time pollution sensors can, therefore, be considered as convenient systems for field experiments where particulate pollution is of special interest, which is the case for runoff waters. Besides which, they are particularly suitable for the control and automation of sanitary transport and treatment equipment, being easily integrated into computerized systems.

scholarly journals Standard and Real-Time Accuracy and Reliability of a Mapping-Grade GPS in a Coniferous Western Oregon Forest

2006 ◽  
Vol 21 (4) ◽  
pp. 222-227 ◽  
Author(s):  
Michael G. Wing ◽  
Richard Karsky
Keyword(s):  
Real Time ◽  
Field Measurements ◽  
Coast Guard ◽  
Young Forest ◽  
Open Canopy ◽  
Standard Configuration ◽  
True Position ◽  
Us Coast Guard ◽  
Differential Corrections ◽  
Time Accuracy

Abstract Accuracy requirements for forested resource measurements can vary greatly depending on analysis and management objectives. Technologies that present efficiencies for reliable measurement collection may help organizations better meet data requirements. We tested the accuracy and reliability of a mapping-grade GPS in a variety of forested conditions in western Oregon. Our objectives were to measure the performance of a GPS operating in a standard configuration and also with real-time US Coast Guard Beacon signals. We also examined the influence of postfield differential corrections and the number of GPS points collected on measurement accuracy and reliability. We found measurement accuracies between 1 and 4 m from true position depending on the amount of canopy closure and the type of GPS configuration. Our results indicated that both standard-mode GPS and US Coast Guard Beacon signals can produce very accurate measurements in open-canopy conditions but are less reliable in young-forest conditions. Postprocessing of field measurements generally yielded improved measurements in young-forest settings but led to slightly reduced accuracies for US Coast Guard Beacon data collected in open-canopy settings. Our results also indicated that collecting a greater number of points does not necessarily lead to improved measurement accuracies. West. J. Appl. For. 21(4):222–227.

scholarly journals Testing GPS generated 1PPS against a rubidium standard

ACTA IMEKO ◽  
2013 ◽  
Vol 2 (1) ◽  
pp. 7 ◽  
Author(s):  
Vukan R Ogrizovic ◽  
Jadranka Marendic ◽  
Snezana Renovica ◽  
Sinis¡a Delcev ◽  
Jelena Gucevic
Keyword(s):  
Real Time ◽  
High Accuracy ◽  
Gps Receiver ◽  
Gps Receivers ◽  
Cycle Slips ◽  
Set Up ◽  
Time Critical

GPS receivers are often used in time-keeping applications, due to their availability, low price and high accuracy. We tested the capability of the GPS receiver to deliver a time-keeping accuracy needed for the time-critical applications, such as astrometry measurements, when a microsecond or better level of accuracy is needed in real-time. We tested a geodetic class GPS receiver against a rubidium standard, over a 24 hours period. In the overall view, the accuracy corresponds to the nominal values. However, we experienced outliers with the certain regularity that we could not explain with cycle-slips or the experiment set-up.

scholarly journals Comparative Study of Positional Accuracies Using Three GPS Receivers

2020 ◽  
Vol 24 (3) ◽  
pp. 443-448
Author(s):  
O.J. Nnamani ◽  
V.A. Ijaware
Keyword(s):  
Global Positioning System ◽  
Vertical Position ◽  
Accurate Information ◽  
Positioning System ◽  
Gps Receiver ◽  
Gps Receivers ◽  
University Of Technology ◽  
Significant Difference ◽  
Global Positioning ◽  
The One

The emergence of the Global Positioning System (GPS) receiver over the years has afforded the avenue to acquire data from various geospatial locations. This paper analyses and compares the accuracy of point positions collected using three Global Positioning System (GPS) receivers— South H66/H88, Sokkia radian IS, and ProMark 3. A field study was conducted on 5 control points within the Federal University of Technology Akure (FUTA) Campus. The One-way ANOVA test performed for the coordinates obtained from the three GPS receivers at an alpha level of 0.05 using SPSS version 16 reveals no statistically significant difference between the coordinates. Analysis of the result shows that South GPS, Sokkia GPS, and ProMark GPS receivers had horizontal misclosure values of 0.1337, 0.1625 and 0.2425 respectively, making South GPS best in obtaining accurate information onhorizontal positions. For the vertical position, misclosure values of 0.0902, 0.2336, and 0.2771 respectively were obtained for the Three GPS receivers, thereby revealing that Sokkia GPS performed optimally in obtaining heights above the ellipsoid. However, as a combination of horizontal and  vertical positions (3-Dimension), Sokkia GPS performed best while ProMark GPS performed averagely and South GPS performed least. This study shows that any of the three GPS receivers can provide reasonable accurate geographic data. However, a definite conclusion remains that the selection of an optimal GPS receiver in this study for any project will largely depend upon the user’s needs and project requirements as the significant variation observed in the height coordinates should be further investigated. Keywords: GPS Receivers, Accuracy, Position Determination, GPS Coordinates

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