title: Determining estuarine seagrass density measures from low altitude multispectral imagery flown by remotely piloted aircraft

authors: Martin, Ross David

subjects: Seagrass

abstract: Seagrass is the subject of significant conservation research. Seagrass is ecologically important and of significant value to human interests. Many seagrass species are thought to be in decline.  Degradation of seagrass populations are linked to anthropogenic environmental issues. Effective management requires robust monitoring that is affordable at large scale. Remote sensing methods using satellite and aircraft imagery enable mapping of seagrass populations at landscape scale. 
Aerial monitoring of a seagrass population can require imagery of high spatial and/or spectral resolution for successful feature extraction across all levels of seagrass density. Remotely piloted aircraft (RPA) can operate close to the ground under precise flight control enabling repeated surveys in high detail with accurate revisit-positioning.
This study evaluates a method for assessing intertidal estuarine seagrass (Zostera muelleri) presence/absence and coverage density using multispectral imagery collected by a remotely piloted aircraft (RPA) flying at 30 m above the estuary surface (2.7 cm ground sampling distance). The research was conducted at Wharekawa Harbour on the eastern coast of the Coromandel Peninsula, North Island, New Zealand.
Differential drainage of residual ebb waters from the surface of an estuary at low tide creates a mosaic of drying sediment, draining surface and static shallow pooling that has potential to interfere with spectral observations. The field surveys demonstrated that despite minor shifts in the spectral coordinates of seagrass and other surface material, there was no apparent difference in image classification outcome from the time of bulk tidal water clearance to the time of returning tidal flood.
For the survey specification tested, classification accuracy increased with decreasing segmentation scale. Pixel-based image analysis (PBIA) achieved higher classification accuracy than object-based image analysis (OBIA) assessed at a range of segmentation scales. Contaminating objects such as shells and detritus can become aggregated within polygon objects when OBIA is applied but remain as isolated objects under PBIA at this image resolution. There was clear separability of spectra for seagrass and sediment, but shell and detritus confounded the classification of seagrass density in some situations.  High density seagrass was distinct from sediment, but classification error arose for sparse seagrass.
Three classifiers (linear discriminant analysis, support vector machine and random forest) and three feature selection options (no selection, collinearity reduction and recursive feature elimination) were assessed for effect on classification performance. The random forest classifier yielded the highest classification accuracy, with no accuracy benefit gained from collinearity reduction or recursive feature elimination. Spectral vegetation indices and texture layers substantially improved classification accuracy. Object geometry made a negligible contribution to classification accuracy using mean-shift segmentation at this image-scale.
The method achieved classification of seagrass density with up to 84% accuracy on a three-tier end-member class scale (low, medium, and high density) when using training data formed using visual interpretation of ground reference photography, and up to 93% accuracy using precisely measured seagrass leaf-area. Visual interpretation agreed with precisely measured seagrass leaf area 88% of the time with some misattribution at mid-density. Visual interpretation was substantially faster to apply than measuring the leaf area. A decile class scale for seagrass density correlated with actual leaf area measures more than the three-tier scale, however, was less accurate for absolute class attribution.
The research demonstrates that seagrass feature extraction from RPA-flown imagery is a feasible and repeatable option for seagrass population monitoring and environmental reporting. Further calibration is required for whole- and multi-estuary application.

text: Determining estuarine seagrass density measures from low altitude multispectral imagery flown by remotely piloted aircraft Seagrass is the subject of significant conservation research. Seagrass is ecologically important and of significant value to human interests. Many seagrass species are thought to be in decline.  Degradation of seagrass populations are linked to anthropogenic environmental issues. Effective management requires robust monitoring that is affordable at large scale. Remote sensing methods using satellite and aircraft imagery enable mapping of seagrass populations at landscape scale. 
Aerial monitoring of a seagrass population can require imagery of high spatial and/or spectral resolution for successful feature extraction across all levels of seagrass density. Remotely piloted aircraft (RPA) can operate close to the ground under precise flight control enabling repeated surveys in high detail with accurate revisit-positioning.
This study evaluates a method for assessing intertidal estuarine seagrass (Zostera muelleri) presence/absence and coverage density using multispectral imagery collected by a remotely piloted aircraft (RPA) flying at 30 m above the estuary surface (2.7 cm ground sampling distance). The research was conducted at Wharekawa Harbour on the eastern coast of the Coromandel Peninsula, North Island, New Zealand.
Differential drainage of residual ebb waters from the surface of an estuary at low tide creates a mosaic of drying sediment, draining surface and static shallow pooling that has potential to interfere with spectral observations. The field surveys demonstrated that despite minor shifts in the spectral coordinates of seagrass and other surface material, there was no apparent difference in image classification outcome from the time of bulk tidal water clearance to the time of returning tidal flood.
For the survey specification tested, classification accuracy increased with decreasing segmentation scale. Pixel-based image analysis (PBIA) achieved higher classification accuracy than object-based image analysis (OBIA) assessed at a range of segmentation scales. Contaminating objects such as shells and detritus can become aggregated within polygon objects when OBIA is applied but remain as isolated objects under PBIA at this image resolution. There was clear separability of spectra for seagrass and sediment, but shell and detritus confounded the classification of seagrass density in some situations.  High density seagrass was distinct from sediment, but classification error arose for sparse seagrass.
Three classifiers (linear discriminant analysis, support vector machine and random forest) and three feature selection options (no selection, collinearity reduction and recursive feature elimination) were assessed for effect on classification performance. The random forest classifier yielded the highest classification accuracy, with no accuracy benefit gained from collinearity reduction or recursive feature elimination. Spectral vegetation indices and texture layers substantially improved classification accuracy. Object geometry made a negligible contribution to classification accuracy using mean-shift segmentation at this image-scale.
The method achieved classification of seagrass density with up to 84% accuracy on a three-tier end-member class scale (low, medium, and high density) when using training data formed using visual interpretation of ground reference photography, and up to 93% accuracy using precisely measured seagrass leaf-area. Visual interpretation agreed with precisely measured seagrass leaf area 88% of the time with some misattribution at mid-density. Visual interpretation was substantially faster to apply than measuring the leaf area. A decile class scale for seagrass density correlated with actual leaf area measures more than the three-tier scale, however, was less accurate for absolute class attribution.
The research demonstrates that seagrass feature extraction from RPA-flown imagery is a feasible and repeatable option for seagrass population monitoring and environmental reporting. Further calibration is required for whole- and multi-estuary application.

year: 2020

title: Tuned in and hands on: Sound designers beyond technical expertise

authors: Delmotte, Isabelle A.

abstract: The term sound designer is a relatively new addition to the professional roles in a film sound crew. Its use can be traced to the 1970s when the dismantlement of some major Hollywood studios gave space for more experimental approaches to film making. A study on acoustic ecologies and cinema sound allowed for creative and altruistic collaborations with some Australian cinema professionals. Subsequent face-to-face interviews and correspondence with the participants to the study pointed to the humanity and concerns at play behind the screen. It is apparent that the capacity of sound designer cannot be pigeonholed: it oscillates according to the demands of a film production and depends on its director’s and financial backers' sonic awareness. Amongst professional sound makers themselves exists a lack of consensus on the role and importance of the position of sound designer. The author proposes a way to lessen professional ambiguity and increase public recognition of atmospheric cinema sound. Invoking atmospheric sound at the inception of an audio-visual narrative could reward its makers and audiences in unsuspected ways. To acknowledge sound designers as architects of sensations and, by the same token, include viscerality and affect as creative elements of film production, could lead to a different appreciation of our lives in sound.

text: Tuned in and hands on: Sound designers beyond technical expertise The term sound designer is a relatively new addition to the professional roles in a film sound crew. Its use can be traced to the 1970s when the dismantlement of some major Hollywood studios gave space for more experimental approaches to film making. A study on acoustic ecologies and cinema sound allowed for creative and altruistic collaborations with some Australian cinema professionals. Subsequent face-to-face interviews and correspondence with the participants to the study pointed to the humanity and concerns at play behind the screen. It is apparent that the capacity of sound designer cannot be pigeonholed: it oscillates according to the demands of a film production and depends on its director’s and financial backers' sonic awareness. Amongst professional sound makers themselves exists a lack of consensus on the role and importance of the position of sound designer. The author proposes a way to lessen professional ambiguity and increase public recognition of atmospheric cinema sound. Invoking atmospheric sound at the inception of an audio-visual narrative could reward its makers and audiences in unsuspected ways. To acknowledge sound designers as architects of sensations and, by the same token, include viscerality and affect as creative elements of film production, could lead to a different appreciation of our lives in sound.

year: 2014

title: Neighbours at Puhoi River: A cross-cultural dual biography of Te Hemara Tauhia(1815-1891) and Martin Krippner(1817-1894)

authors: Eddy, Anne

subjects: Cross-cultural

abstract: This thesis seeks to re-construct the biographies of two relatively obscure, yet fascinating and controversial players in the history of Aotearoa New Zealand. Both historical figures were initiators and leaders of neighbouring settlements: the rangatira, Te Hemara Tauhia (1815 – 1891), in his role as chief of the Te Kawerau/Ngāti Rongo hapū of the Ngāti Whātua iwi, re-occupying ancestral lands after living in captivity with Ngāpuhi, and the former Austrian captain, Martin Krippner (1817 – 1894), organiser of an Austrian-Bohemian settlement made possible under the Auckland Provincial Government land grant scheme. Despite their efforts for each community, both men were accused by their own people of misusing their positions for personal gains. Te Hemara Tauhia was blamed for selling off tribal lands to cover personal debts. Martin Krippner was never forgiven for promising his Bohemian compatriots a ‘land of milk and honey’ while leading them to near starvation and struggle within dense New Zealand bush, and subsequently into war in the Waikato where Krippner was commissioned captain in the Waikato Militia.
Focussing on three main objectives, this cross-cultural dual biography provides an original contribution to historical scholarship: Firstly, it looks behind the myths that have been created around Te Hemara Tauhia and Martin Krippner; it thoroughly examines what both men did and how social, economic and political circumstances influenced their motivations and choices at that particular time. Secondly, placing Tauhia’s and Krippner’s biographies side-by-side provides a novel view of a range of historical phenomena from both Tangata Whenua (indigenous peoples) and European settlers (Pākehā) perspectives. Looking at the same events from different angles and perspectives, a cross-cultural, dual biography can act like a prismatic tool, revealing the complexity of a shared history. The third aim of this research encompasses my intention to contribute to and to participate in a dialogue between ethnic groups in Aotearoa New Zealand, especially between Māori and Pākehā, in order to challenge stereotypes and generalisations based on lack of knowledge of historical and cultural contexts.

text: Neighbours at Puhoi River: A cross-cultural dual biography of Te Hemara Tauhia(1815-1891) and Martin Krippner(1817-1894) This thesis seeks to re-construct the biographies of two relatively obscure, yet fascinating and controversial players in the history of Aotearoa New Zealand. Both historical figures were initiators and leaders of neighbouring settlements: the rangatira, Te Hemara Tauhia (1815 – 1891), in his role as chief of the Te Kawerau/Ngāti Rongo hapū of the Ngāti Whātua iwi, re-occupying ancestral lands after living in captivity with Ngāpuhi, and the former Austrian captain, Martin Krippner (1817 – 1894), organiser of an Austrian-Bohemian settlement made possible under the Auckland Provincial Government land grant scheme. Despite their efforts for each community, both men were accused by their own people of misusing their positions for personal gains. Te Hemara Tauhia was blamed for selling off tribal lands to cover personal debts. Martin Krippner was never forgiven for promising his Bohemian compatriots a ‘land of milk and honey’ while leading them to near starvation and struggle within dense New Zealand bush, and subsequently into war in the Waikato where Krippner was commissioned captain in the Waikato Militia.
Focussing on three main objectives, this cross-cultural dual biography provides an original contribution to historical scholarship: Firstly, it looks behind the myths that have been created around Te Hemara Tauhia and Martin Krippner; it thoroughly examines what both men did and how social, economic and political circumstances influenced their motivations and choices at that particular time. Secondly, placing Tauhia’s and Krippner’s biographies side-by-side provides a novel view of a range of historical phenomena from both Tangata Whenua (indigenous peoples) and European settlers (Pākehā) perspectives. Looking at the same events from different angles and perspectives, a cross-cultural, dual biography can act like a prismatic tool, revealing the complexity of a shared history. The third aim of this research encompasses my intention to contribute to and to participate in a dialogue between ethnic groups in Aotearoa New Zealand, especially between Māori and Pākehā, in order to challenge stereotypes and generalisations based on lack of knowledge of historical and cultural contexts.

year: 2017