title: The efficacy of path loss models for fixed rural wireless links

authors: Phillips, Caleb

subjects: computer science

abstract: In this paper we make use of a large set of measurements from a production wireless network in rural New Zealand to analyze the performance of 28 path loss prediction models, published over the course of 60 years. We propose five metrics to determine the performance of each model. We show that the state of the art, even for the “simple” case of rural environments, is surprisingly ill-equipped to make accurate predictions. After combining the best elements of the best models and hand-tuning their parameters, we are unable to achieve an accuracy of better than 12 dB root mean squared error (RMSE)—four orders of magnitude away from ground truth.

text: The efficacy of path loss models for fixed rural wireless links In this paper we make use of a large set of measurements from a production wireless network in rural New Zealand to analyze the performance of 28 path loss prediction models, published over the course of 60 years. We propose five metrics to determine the performance of each model. We show that the state of the art, even for the “simple” case of rural environments, is surprisingly ill-equipped to make accurate predictions. After combining the best elements of the best models and hand-tuning their parameters, we are unable to achieve an accuracy of better than 12 dB root mean squared error (RMSE)—four orders of magnitude away from ground truth.

year: 2011

title: Investigating the vertical structure of sediment fluxes across an intertidal mudflat

authors: Beisly, Toby

subjects: Oceanography

abstract: Muddy coastal environments consisting of fine grained, cohesive sediment, are important systems for their provision of crucial ecosystem services and unique ecology. Such environments are governed by complex sediment transport patterns connecting the system to the wider coastal environment. To understand sediment transport it is necessary to measure suspended sediment concentrations and current velocities, from which, sediment fluxes can be estimated. Measurements of suspended sediment concentration (SSC) are typically carried out through the use of a variety of instruments, including, optical backscatter sensors or acoustic backscatter sensors; while acoustic doppler velocimeters, electromagnetic current meters and acoustic doppler current profilers are used to provide measurements of flow velocities.  
To reliably estimate sediment flux, accurate vertical profiles of SSC and currents are required. Despite the need for profile information, typically flux calculations are based on observations from a single measurement location and exploited through the water column. However, the sensitivity of flux measurements to the vertical resolution (e.g., number of instruments) or to the method of extrapolation is rarely quantified. 
This study elucidates the significant sensitivity of measurements to the instrument arrangement and technique used to extrapolate the data. Our results, taken in the field under real life conditions, indicate that single, or even double, vertical instrument arrangements are likely to have a large margin of error associated with any resulting flux estimates. However, a more even spread of instruments over the water column appears to give a more accurate estimate of flux. We find that under calm conditions (small waves) the Rouse SSC models provide a good estimate of SSC while the velocity model; law of the wall, contains significant uncertainty in its velocity estimates. These results demonstrate the uncertainty associated with such dynamic environments, and as such, the need for robust measurement techniques and an understanding of the vertical structure of SSC and currents. Such understanding of sediment transport is crucial for making informed decisions around the management of intertidal muddy environments.

text: Investigating the vertical structure of sediment fluxes across an intertidal mudflat Muddy coastal environments consisting of fine grained, cohesive sediment, are important systems for their provision of crucial ecosystem services and unique ecology. Such environments are governed by complex sediment transport patterns connecting the system to the wider coastal environment. To understand sediment transport it is necessary to measure suspended sediment concentrations and current velocities, from which, sediment fluxes can be estimated. Measurements of suspended sediment concentration (SSC) are typically carried out through the use of a variety of instruments, including, optical backscatter sensors or acoustic backscatter sensors; while acoustic doppler velocimeters, electromagnetic current meters and acoustic doppler current profilers are used to provide measurements of flow velocities.  
To reliably estimate sediment flux, accurate vertical profiles of SSC and currents are required. Despite the need for profile information, typically flux calculations are based on observations from a single measurement location and exploited through the water column. However, the sensitivity of flux measurements to the vertical resolution (e.g., number of instruments) or to the method of extrapolation is rarely quantified. 
This study elucidates the significant sensitivity of measurements to the instrument arrangement and technique used to extrapolate the data. Our results, taken in the field under real life conditions, indicate that single, or even double, vertical instrument arrangements are likely to have a large margin of error associated with any resulting flux estimates. However, a more even spread of instruments over the water column appears to give a more accurate estimate of flux. We find that under calm conditions (small waves) the Rouse SSC models provide a good estimate of SSC while the velocity model; law of the wall, contains significant uncertainty in its velocity estimates. These results demonstrate the uncertainty associated with such dynamic environments, and as such, the need for robust measurement techniques and an understanding of the vertical structure of SSC and currents. Such understanding of sediment transport is crucial for making informed decisions around the management of intertidal muddy environments.

year: 2023

title: Piri Pāua: Mātauranga Māori and marine science approach to growth rate and length at maturity of pāua in the Bay of Plenty 2022-2024

authors: Paul-Burke, Kura

abstract: Pāua is a highly regarded taonga (culturally important) species. Mai i ngā Kurī ā Whārei ki Tihirau (the Bay of Plenty Regional Iwi Customary Fisheries Forum) raised concerns about the current state of pāua in Te Moana-a-Toi (Bay of Plenty). This project utilised localised intergenerational observations of population dynamics in traditional harvesting areas to assess pāua productivity in the Tauranga Moana Mātaitai Reserve in Tauranga and Te Rohe Moana o Ngāti Awa in Whakatāne. The project combined mātauranga Māori alongside marine science field methods.

Results were compared with previous iwi-led research at Tauranga in 2013 and Whakatāne in 2010. The pāua population in 2023 had declined by almost half in Tauranga but remained relatively consistent across all sites in Whakatāne. However, pāua were small sized in both locations, with less than 1% of individuals reaching the Minimum Legal Size (125 mm) for harvesting. Growth rate surveys were conducted in the wild at both locations from June 2023 to the end of May 2024 and identified pāua as slow growing and, as a result, sexually mature at smaller sizes than in other regions of Aotearoa New Zealand.

text: Piri Pāua: Mātauranga Māori and marine science approach to growth rate and length at maturity of pāua in the Bay of Plenty 2022-2024 Pāua is a highly regarded taonga (culturally important) species. Mai i ngā Kurī ā Whārei ki Tihirau (the Bay of Plenty Regional Iwi Customary Fisheries Forum) raised concerns about the current state of pāua in Te Moana-a-Toi (Bay of Plenty). This project utilised localised intergenerational observations of population dynamics in traditional harvesting areas to assess pāua productivity in the Tauranga Moana Mātaitai Reserve in Tauranga and Te Rohe Moana o Ngāti Awa in Whakatāne. The project combined mātauranga Māori alongside marine science field methods.

Results were compared with previous iwi-led research at Tauranga in 2013 and Whakatāne in 2010. The pāua population in 2023 had declined by almost half in Tauranga but remained relatively consistent across all sites in Whakatāne. However, pāua were small sized in both locations, with less than 1% of individuals reaching the Minimum Legal Size (125 mm) for harvesting. Growth rate surveys were conducted in the wild at both locations from June 2023 to the end of May 2024 and identified pāua as slow growing and, as a result, sexually mature at smaller sizes than in other regions of Aotearoa New Zealand.

year: 2025