Screening GPS telemetry data for locations having unacceptable error

Laver, Pete N.; Powell, Roger A.; Alexander, Kathleen A.

doi:10.1016/j.ecoinf.2015.02.001

Cited by 15 publications

(14 citation statements)

References 35 publications

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“…However, the relationship between location error and DOP can be extremely weak [ 30 ], resulting in either rejection of accurate data or inclusion of inaccurate data. Novel approaches to filtering data by comparing altitude values derived from a digital elevation model (DEM) to those from the GPS device for the same location have been proposed [ 31 ]. This approach was used with ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) Version 3 Digital Elevation Model (DEM) data, excluding GPS point data that varied by more than 100 m from the DEM in elevation.…”

Section: Methodsmentioning

confidence: 99%

Post-Release Monitoring of Western Grey Kangaroos (Macropus fuliginosus) Relocated from an Urban Development Site

Cowan¹,

Blythman²,

Angus³

et al. 2020

Animals

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The expansion of urban areas and associated clearing of habitat can have severe consequences for native wildlife. One option for managing wildlife in these situations is to relocate them. While there is a general perception that relocation is humane, transparency of outcomes is lacking. Here, we document the outcome of 122 western grey kangaroos (Macropus fuliginosus) relocated from an urban development site on the edge of Perth, Western Australia. Global Positioning System (GPS) or Very High Frequency (VHF) collars were fitted to 67 kangaroos, and their survival and movement were monitored over 12 months using telemetry, camera traps and spotlighting. Only six collared animals survived for the duration of the study with most dying within a week of the relocation, indicating stress associated with capture as the likely cause. By the completion of the study, 111 kangaroos were predicted to have died based on the proportion of individuals known to have died. Movement patterns of surviving GPS collared kangaroos changed over time from largely exploratory forays, to more repeated movements between focus areas within home ranges. The poor outcome here raises concerns around the viability of relocating a relatively large number of kangaroos as a management option. It also highlights the need for careful planning to limit the stress associated with capture and transport if relocations are to be used for managing kangaroos in urban areas.

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Section: Methodsmentioning

confidence: 99%

Post-Release Monitoring of Western Grey Kangaroos (Macropus fuliginosus) Relocated from an Urban Development Site

Cowan¹,

Blythman²,

Angus³

et al. 2020

Animals

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“…Therefore, we suggest that recommendations for handling data with respect to DOP are likely to apply to EHPE as well (for example, see [ 21 , 23 , 24 ]). Recently, Laver et al [ 33 ] suggested evaluation of multiple screening metrics (i.e., DOP, number of satellites, fix dimension (2D or 3D), estimated elevation error) in an information-theoretic framework to determine which screening metrics are best-suited for screening data from individual study sites. For data collected from GPS loggers using SiRF iii chipsets, EHPE is likely to provide an additional metric for such evaluation.…”

Section: Discussionmentioning

confidence: 99%

Assessment of accuracy, fix success rate, and use of estimated horizontal position error (EHPE) to filter inaccurate data collected by a common commercially available GPS logger

Morris

Conner

2017

PLoS ONE

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Global positioning system (GPS) technologies have improved the ability of researchers to monitor wildlife; however, use of these technologies is often limited by monetary costs. Some researchers have begun to use commercially available GPS loggers as a less expensive means of tracking wildlife, but data regarding performance of these devices are limited. We tested a commercially available GPS logger (i–gotU GT–120) by placing loggers at ground control points with locations known to < 30 cm. In a preliminary investigation, we collected locations every 15 minutes for several days to estimate location error (LE) and circular error probable (CEP). Using similar methods, we then investigated the influence of cover on LE, CEP, and fix success rate (FSR) by constructing cover over ground control points. We found mean LE was < 10 m and mean 50% CEP was < 7 m. FSR was not significantly influenced by cover and in all treatments remained near 100%. Cover had a minor but significant effect on LE. Denser cover was associated with higher mean LE, but the difference in LE between the no cover and highest cover treatments was only 2.2 m. Finally, the most commonly used commercially available devices provide a measure of estimated horizontal position error (EHPE) which potentially may be used to filter inaccurate locations. Using data combined from the preliminary and cover investigations, we modeled LE as a function of EHPE and number of satellites. We found support for use of both EHPE and number of satellites in predicting LE; however, use of EHPE to filter inaccurate locations resulted in the loss of many locations with low error in return for only modest improvements in LE. Even without filtering, the accuracy of the logger was likely sufficient for studies which can accept average location errors of approximately 10 m.

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“…For each treatment, we calculated the mean, standard deviation (SD), and range of GPS error in each dimension. Dilution of precision (DOP) measures have been suggested as a potential means of filtering inaccurate GPS locations (D'eon and Delparte 2005), although more recent studies have called into question the usefulness of this approach (Recio et al 2011, Laver et al 2015. To illustrate the relationship between DOP and GPS error for these transmitters, we plotted horizontal error and the absolute value of vertical error as a function of horizontal dilution of precision (HDOP) and vertical dilution of precision (VDOP), respectively.…”

Section: Static Testsmentioning

confidence: 99%

“…We then applied a speed filter (McConnell et al 1992) to remove locations associated with estimated mean minimum horizontal flight speeds !90 km hr À1 , a conservative cutoff speed for filtering outlier locations based on previous speed estimates of migrating Turkey Vultures (Mandel et al 2008, Dodge et al 2014. This had the effect of removing the most extreme outliers without also removing a large number of reasonable locations, a potential issue with filtering based on DOP metrics (Laver et al 2015). To estimate height above ground, we calculated the difference between each postfiltered GPS location and elevation based on U.S. Geological Survey (USGS) 1/3 arc-second seamless digital elevation models (DEM;~10 m 2 resolution; http://viewer.…”

Section: Field Testsmentioning

confidence: 99%

“…Although earlier studies have suggested that screening GPS data by removing locations with DOP values above an arbitrary cutoff may effectively remove outliers and reduce mean location error (D'eon and Delparte 2005, Lewis et al 2007), more recent work has demonstrated that, since the removal of GPS Selective Availability, DOP is less reliable for identifying large GPS errors (Recio et al 2011, Laver et al 2015, and that screening based solely on DOP may come at the cost of removing many accurate locations with little gain in error reduction. We advise against filtering based solely on DOP values and suggest that any screening incorporate multiple conditions or, ideally, take a modelbased approach to identifying unacceptable location error, sensu Laver et al (2015). We suggest that this applies to all modern GPS telemetry technology and not just the transmitters that we tested.…”

Section: Gps Accuracymentioning

confidence: 99%

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Environmental conditions and animal behavior influence performance of solar-powered GPS-GSM transmitters

et al. 2017

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Screening GPS telemetry data for locations having unacceptable error

Cited by 15 publications

References 35 publications

Post-Release Monitoring of Western Grey Kangaroos (Macropus fuliginosus) Relocated from an Urban Development Site

Post-Release Monitoring of Western Grey Kangaroos (Macropus fuliginosus) Relocated from an Urban Development Site

Assessment of accuracy, fix success rate, and use of estimated horizontal position error (EHPE) to filter inaccurate data collected by a common commercially available GPS logger

Environmental conditions and animal behavior influence performance of solar-powered GPS-GSM transmitters

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