title: An examination of the causes of heading bias in computer simulated self-motion

authors: Kim, Ruth Susan

abstract: A series of experiments were devised in order to examine aspects of human visual performance during simulated self-motion. The experimental stimuli were computer simulations of observer translational motion through a 3-D random dot cloud. Experiments were specifically designed to obtain data regarding the problem of bias in judgments of heading, and to determine the influence of various experimental factors upon the bias. A secondary aim was to use these results to develop a workable computer model to predict such bias in heading estimation. 
Heading bias has been known for many years, but it is generally assumed only to be a problem for complex observer motion. However, the current work involved simple observer translation, and found a significant amount of heading bias. A wide variety of experimental factors were examined, and it was found that scene depth and speed had the greatest effect upon the accuracy of heading estimates, with a faster speed or smaller depth reducing bias. 
It was proposed that yaw eye movements, driven by the rotational component of radial flow, were responsible for the bias. An adaptation of the Perrone (1992) model of heading was used to model this, and a highly significant correlation was obtained between the experimental data and the predictions of the model.

text: An examination of the causes of heading bias in computer simulated self-motion A series of experiments were devised in order to examine aspects of human visual performance during simulated self-motion. The experimental stimuli were computer simulations of observer translational motion through a 3-D random dot cloud. Experiments were specifically designed to obtain data regarding the problem of bias in judgments of heading, and to determine the influence of various experimental factors upon the bias. A secondary aim was to use these results to develop a workable computer model to predict such bias in heading estimation. 
Heading bias has been known for many years, but it is generally assumed only to be a problem for complex observer motion. However, the current work involved simple observer translation, and found a significant amount of heading bias. A wide variety of experimental factors were examined, and it was found that scene depth and speed had the greatest effect upon the accuracy of heading estimates, with a faster speed or smaller depth reducing bias. 
It was proposed that yaw eye movements, driven by the rotational component of radial flow, were responsible for the bias. An adaptation of the Perrone (1992) model of heading was used to model this, and a highly significant correlation was obtained between the experimental data and the predictions of the model.

year: 2003

title: Nitrogen leaching from effluent irrigated pasture

authors: Treweek, Glen

subjects: sewage

abstract: The surface waters of the Taupo region are of high quality and are sensitive to inputs of nitrogen. To reduce the amount of nitrogen discharged to surface water, the Taupo District Council (TDC) has employed a land treatment scheme (LTS), where treated municipal wastewater is irrigated onto ryegrass pasture. To limit the possibility of nitrogen pollution, regulations govern the amount of effluent that TDC may irrigate. This study reports the results from the first year of a five year trial where nitrogen leaching from the Taupo LTS was measured.
To measure nitrogen leaching from the Taupo LTS, 48 intact monolith lysimeters were installed beneath effluent irrigation from two centre pivot irrigators. Four treatments based on nitrogen loading rates were trialled, nominally no-N (0 kg N ha-¹yr-¹), low-N (350 kg N ha-¹yr-¹ or less), mid-N (between 350 and 450 kg N ha-¹yr-¹), and high-N (greater than 450 kg N ha-¹yr-¹). Leachate was collected at least monthly and analysed for total nitrogen (TN), nitrate/nitrite nitrogen (NO₃-N), ammoniacal nitrogen (NH₄-N), dissolved organic nitrogen (DON), and total Kjeldahl nitrogen (TKN). The pasture was removed from the lysimeters to determine dry-matter production and pasture nitrogen concentration to calculate nitrogen uptake.
Effluent irrigation significantly increased pasture growth and nitrogen leaching compared to the un-irrigated treatments (P<0.001). The mean rate of pasture growth from the irrigated treatments was 15,800 ± 1,700 kg DM ha-¹yr-¹, but there were no significant difference between the rate of pasture growth between the irrigated treatments. The pasture of the high-N treatments had a significantly higher nitrogen concentration than the low-N treatments (P<0.001), consequently the high-N treatment removed 390 kg N ha-¹, compared to 310 kg N ha-¹ removed from the mid-N and low-N treatments. On average, the pasture removed 84 % of the nitrogen that was irrigated.
After 12 months, the no-N treatments leached 5 ± 3 kg TN ha-¹, the low-N treatment leached 15 ± 1 kg TN ha-¹, the mid-N treatment leached 17 ± 8 kg TN ha-¹, and the high-N treatment leached 26 ± 4 kg TN ha-¹. The high-N treatments leached significantly more TN than the low-N (P<0.005), but there was no significant difference in TN leached between the high-N and mid-N, or the mid-N and low-N treatments. The TN leached was poorly correlated with the rate of effluent irrigation. TN leached was positively correlated with the volume of water that drained through the soil (R2=0.7). The nitrogen in the leachate of the irrigated treatments comprised on average, 53 % NO₃-N, and 45 % DON, while the leachate of the un-irrigated treatments comprised, on average, 26 % NO₃-N and 72 % DON. NH₄-N accounted for approximately 2% of all nitrogen leached. Most of the NO₃-N leached throughout the year was leached after rain during summer and autumn. The mean concentration of NO₃-N leached from the irrigated treatments was 1.3 g N m-³. The concentration of NO₃-N in the leachate never exceeded Ministry of Health guidelines (11.3 g N m-³). The mean concentration of DON leached from the irrigated treatments was 1.2 g N m-³.
Removing nitrogen in the pasture is the solution to avoid excess nitrogen leaching from the Taupo LTS. There is potential to recover more nitrogen in the pasture by improving the pasture cover and frequency of harvest.

text: Nitrogen leaching from effluent irrigated pasture The surface waters of the Taupo region are of high quality and are sensitive to inputs of nitrogen. To reduce the amount of nitrogen discharged to surface water, the Taupo District Council (TDC) has employed a land treatment scheme (LTS), where treated municipal wastewater is irrigated onto ryegrass pasture. To limit the possibility of nitrogen pollution, regulations govern the amount of effluent that TDC may irrigate. This study reports the results from the first year of a five year trial where nitrogen leaching from the Taupo LTS was measured.
To measure nitrogen leaching from the Taupo LTS, 48 intact monolith lysimeters were installed beneath effluent irrigation from two centre pivot irrigators. Four treatments based on nitrogen loading rates were trialled, nominally no-N (0 kg N ha-¹yr-¹), low-N (350 kg N ha-¹yr-¹ or less), mid-N (between 350 and 450 kg N ha-¹yr-¹), and high-N (greater than 450 kg N ha-¹yr-¹). Leachate was collected at least monthly and analysed for total nitrogen (TN), nitrate/nitrite nitrogen (NO₃-N), ammoniacal nitrogen (NH₄-N), dissolved organic nitrogen (DON), and total Kjeldahl nitrogen (TKN). The pasture was removed from the lysimeters to determine dry-matter production and pasture nitrogen concentration to calculate nitrogen uptake.
Effluent irrigation significantly increased pasture growth and nitrogen leaching compared to the un-irrigated treatments (P<0.001). The mean rate of pasture growth from the irrigated treatments was 15,800 ± 1,700 kg DM ha-¹yr-¹, but there were no significant difference between the rate of pasture growth between the irrigated treatments. The pasture of the high-N treatments had a significantly higher nitrogen concentration than the low-N treatments (P<0.001), consequently the high-N treatment removed 390 kg N ha-¹, compared to 310 kg N ha-¹ removed from the mid-N and low-N treatments. On average, the pasture removed 84 % of the nitrogen that was irrigated.
After 12 months, the no-N treatments leached 5 ± 3 kg TN ha-¹, the low-N treatment leached 15 ± 1 kg TN ha-¹, the mid-N treatment leached 17 ± 8 kg TN ha-¹, and the high-N treatment leached 26 ± 4 kg TN ha-¹. The high-N treatments leached significantly more TN than the low-N (P<0.005), but there was no significant difference in TN leached between the high-N and mid-N, or the mid-N and low-N treatments. The TN leached was poorly correlated with the rate of effluent irrigation. TN leached was positively correlated with the volume of water that drained through the soil (R2=0.7). The nitrogen in the leachate of the irrigated treatments comprised on average, 53 % NO₃-N, and 45 % DON, while the leachate of the un-irrigated treatments comprised, on average, 26 % NO₃-N and 72 % DON. NH₄-N accounted for approximately 2% of all nitrogen leached. Most of the NO₃-N leached throughout the year was leached after rain during summer and autumn. The mean concentration of NO₃-N leached from the irrigated treatments was 1.3 g N m-³. The concentration of NO₃-N in the leachate never exceeded Ministry of Health guidelines (11.3 g N m-³). The mean concentration of DON leached from the irrigated treatments was 1.2 g N m-³.
Removing nitrogen in the pasture is the solution to avoid excess nitrogen leaching from the Taupo LTS. There is potential to recover more nitrogen in the pasture by improving the pasture cover and frequency of harvest.

year: 2011

title: A brief history of Whakapapa: Māori approaches to genealogy

authors: Mahuika, Nepia

subjects: whakapapa

abstract: Whakapapa is the Māori term for genealogy. It has been described by some as the skeletal structure of Maori epistemology because all things have their own genealogies. In research, whakapapa has been presented in tribal histories, Maori Land Court records, and consistently as a framework for matauranga Māori (Māori knowledge) and Māori research methodologies. This essay offers a brief overview of the ways in which whakapapa has been understood and negotiated in research particularly after the arrival of Europeans. Some early ethnographers, for instance, applied their own genealogical methods of dating to whakapapa, which influenced various Māori approaches from the twentieth century. With the advent of literacy and print, Māori experimented with new ways to record genealogy, and yet the underlying oral, ethical, and cultural practices that are crucial to whakapapa have remained integral to how it still lives and operates in Maori communities today.

text: A brief history of Whakapapa: Māori approaches to genealogy Whakapapa is the Māori term for genealogy. It has been described by some as the skeletal structure of Maori epistemology because all things have their own genealogies. In research, whakapapa has been presented in tribal histories, Maori Land Court records, and consistently as a framework for matauranga Māori (Māori knowledge) and Māori research methodologies. This essay offers a brief overview of the ways in which whakapapa has been understood and negotiated in research particularly after the arrival of Europeans. Some early ethnographers, for instance, applied their own genealogical methods of dating to whakapapa, which influenced various Māori approaches from the twentieth century. With the advent of literacy and print, Māori experimented with new ways to record genealogy, and yet the underlying oral, ethical, and cultural practices that are crucial to whakapapa have remained integral to how it still lives and operates in Maori communities today.

year: 2019