Methods River Conservation Area Drone Survey Alvin Chin, Justin Martinez, Donna Climent, Eva Tillett Advanced Geomatics Spring 2019 Introduction & Objective Methods and Materials This project was divided into four phases: Plan Approval, Site Preparation, Flight, and Image Processing. Drone flights are subject to both the Federal Aviation Regulations (“Part 107”) and New Jersey state statute (P.L.2017, c.315). Off-campus drone flights by Rutgers researchers also require review by RU Environmental Health and Safety and RU Risk Management.[13] We submitted a flight plan that included a site map, regional flight hazards and sensitive areas, permission from the property-owner, FAA pilot certification, drone aircraft registration certification, and drone technical specifications. Per the plan, we informed local stakeholders, including a public utility with significant electrical infrastructure in the vicinity of the wetland site. As a capability-building exercise, we flew a practice flight at an athletic field on campus which also required a flight plan submission. Our drone model was a DJI Inspire 1 Pro, equipped with a DJI FC550 camera. To prepare the site, we cleared narrow footpaths starting from a gravel road along the wetland’s southern edge, going north through the phragmites vegetation. Along these paths, we cleared wider areas to ensure that a Ground Control Point marker (GCP) placed on the ground would have a line of sight to the survey drone. 8 GCPs were constructed from 3x4 ft salvaged cardboard and paper; it was thought this would be a sufficient quantity.[14] Their locations were recorded using a handheld GPS receiver. On the day of flight, flight missions were programmed into the drone using Pix4Dcapture drone flightplan software. To account for limited flight endurance, the survey was divided into four missions of 16 minutes or less. Before the first mission, the drone’s GPS was calibrated. Each flight was launched from a nearby point along the southern road. 859 images were transferred from the drone camera to the Rutgers CRSSA computer server. There, the images were separated into groups by flight mission, and the image groups were concurrently processed on adjacent workstations using Pix4Dmapper software. After GCPs and supplemental manually-added tie points were linked in all images, the group links were merged and the full image set was processed using the merged link set. A Digital Elevation Model and photomosaic were generated. Conclusions -Add more GCPs to field for more accurate drone maps -Calibrate camera -More developed Pix4D application (malfunctions impaired results) -Longer battery life for a continuous flight project -Better field clearing technique -Account for variation in weather, tide, illumination, and seasonality Acknowledgements References Camera Flight Positions & Image Processing Results Our goal is to create a 3-dimensional spatial model as a reference for long-term monitoring studies at the New Brunswick River Conservation Area wetland in the city of New Brunswick, NJ. The site includes ~40 acres of wetland, including a tidally-influenced slough and dense vegetative cover of Phragmites australis. Phragmites australis is a widespread wetland reed that maintains some ecosystem services, including sediment stabilization, but reduces fish habitat and may decrease biodiversity.[1] Phragmites may also increase drainage and oxidation, increasing subsidence.[2] Given climate change-induced rises in storm frequency and water elevations, phragmites wetlands may be a valuable natural mitigator during extreme weather events.[3] Previous research has found that phragmites wetlands “actively resist the deleterious effects of sea-level rise” and that phragmites is “likely to stabilize tidal wetlands because of traits that support higher below-ground productivity than the vegetation they are replacing.”[4] Nonetheless, wetland elevation is a site-sensitive function of the interdependent factors of organic material inputs, sediment deposition, and soil porosity; accumulated phragmites litter may increase elevation, but deprive the wetland of depositional inputs.[5] In these cases where a high spatial resolution is needed, a small unmanned aircraft, or drone, is a useful platform to map changes in wetlands using structure-from-motion photogrammetry.[6] Drone-based remote sensing has been used to measure phragmites heights[7], create digital surface models[8], and digital terrain models despite dense vegetation cover[9]. However, coastal wetlands surveys may require flexible and rapid deployment of sampling missions[10], and extensive image post-processing.[11,12] We propose to collect imagery with a drone (operated by the Rutgers-NJ Agricultural Experiment Station’s Office of Research Analytics), and process it into a 3-dimensional model that can be used as a reference for future changes in wetland extent and elevation. GCP marker with Bad Elf GPS unit Clearing vegetation for accessibility; Track of pathways cleared and GCP locations Pix4D with four overlapping flight plans We would like to thank Lucas Marxen, Dan Farnsworth, Alejandro Ruiz, and Rick Lathrop for their assistance [1] Raichel, DL; Able, KW; & Hartman, JM. Estuaries (2003) 26: 511. See also Yuhas, CE; Hartman, JM; & Weis, JS. Urban Habitats (2005) 3:158-191 . [2] Chambers, RM; Meyerson, LA; & Saltonstall, K. (1999) Expansion of Phragmites australis into tidal wetlands of North America. Aquatic Botany 64:261–273. [3] Weis, J. April 3, 2019. “As climate change erodes US coastlines, an invasive plant could become an ally.” The Conversation. https://theconversation.com/as-climate-change-erodes-us-coastlines-an-invasive-plant-could-become-an-ally-111162 Accessed 5 April 2019. [4] Kirwan, ML & Megonigal, J.P. (2013) Tidal wetland stability in the face of human impacts and sea-level rise. Nature 504 (7478):53 . [5] Karstens, S; Jurasinski, G; Glatzel, S; & Buczko, U. (2016) Dynamics of surface elevation and microtopography in different zones of a coastal Phragmites wetland. Ecological Engineering. 94:152-163. [6] Kalacskaa, M; Chmura, G.L; Lucanus, O; Bérubé, D; & Arroyo-Mora, J.P. (2017) Structure from motion will revolutionize analyses of tidal wetland landscapes. Remote Sensing of Environment. Volume 199, 15 Sept, pp.14-24. [7] Meneses, NC; Baier, S.; Reidelstürz, P.; Geist, J.; & Schneider, T. (2018) Modelling heights of sparse aquatic reed (Phragmites australis) using Structure from Motion point clouds derived from Rotary- and Fixed-Wing Unmanned Aerial Vehicle (UAV) data. Limnologica 72, pp.10-21. [8] Samiappan, S; Turnage, G; Hathcock, LA; & Moorhead, R. (2017) Mapping of invasive phragmites (common reed) in Gulf of Mexico coastal wetlands using multispectral imagery and small unmanned aerial systems. International Journal of Remote Sensing, 38:8-10, 2861-2882. [9] Meng, X; Shang, N; Zhang, X; Li, C; Zhao, K; Qiu, X; & Weeks, E. (2017) Photogrammetric UAV Mapping of Terrain under Dense Coastal Vegetation: An Object-Oriented Classification Ensemble Algorithm for Classification and Terrain Correction. Remote Sensing, 9(11), 1187. [10] Doughty, CL & Cavanaugh, K. (2019) Mapping Coastal Wetland Biomass from High Resolution Unmanned Aerial Vehicle (UAV) Imagery. Remote Sensing 11(5):540. [11] Bhatt, P. (2018) Mapping Coastal Wetland and Phragmites on the Hiawatha National Forest Using Unmanned Aerial System (UAS) Imagery: Proof of Concepts. Michigan Technological University, ProQuest Dissertations Publishing. 13421185. [12] Thornton, V. (2018) Determining Tidal Characteristics In a Restored Tidal Wetland Using Unmanned Aerial Vehicles and Derived Data. Virginia Commonwealth University, VCU Scholars Compass Theses and Dissertations. [13] Lai, Jonathan. “Rutgers bans drones on campus.” 4 Apr 2016. Philadelphia Inquirer. [14] Pix4d Blog. “Do more GCPs equal more accurate drone maps?” 5 Nov 2018. https ://www.pix4d.com/blog/GCP-accuracy- drone-maps Accessed April 2019. Locations of: images (red) taken by drone. GCPs and manually-added tie points (blue) Final mosaic output of entire wetland Final DEM (digital elevation model) output of entire wetland 100m
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Methods
River Conservation Area Drone SurveyAlvin Chin, Justin Martinez, Donna Climent, Eva Tillett
Advanced Geomatics Spring 2019
Introduction & Objective
Methods and MaterialsThis project was divided into four phases: Plan Approval, Site Preparation, Flight, and Image Processing.
Drone flights are subject to both the Federal Aviation Regulations (“Part 107”) and New Jersey state statute (P.L.2017, c.315). Off-campus drone flights by Rutgers researchers also require review by RU Environmental Health and Safety and RU Risk Management.[13] We submitted a flight plan that included a site map, regional flight hazards and sensitive areas, permission from the property-owner, FAA pilot certification, drone aircraft registration certification, and drone technical specifications. Per the plan, we informed local stakeholders, including a public utility with significant electrical infrastructure in the vicinity of the wetland site. As a capability-building exercise, we flew a practice flight at an athletic field on campus which also required a flight plan submission. Our drone model was a DJI Inspire 1 Pro, equipped with a DJI FC550 camera.
To prepare the site, we cleared narrow footpaths starting from a gravel road along the wetland’s southern edge, going north through the phragmites vegetation. Along these paths, we cleared wider areas to ensure that a Ground Control Point marker (GCP) placed on the ground would have a line of sight to the survey drone. 8 GCPs were constructed from 3x4 ft salvaged cardboard and paper; it was thought this would be a sufficient quantity.[14] Their locations were recorded using a handheld GPS receiver.
On the day of flight, flight missions were programmed into the drone using Pix4Dcapture drone flightplansoftware. To account for limited flight endurance, the survey was divided into four missions of 16 minutes or less. Before the first mission, the drone’s GPS was calibrated. Each flight was launched from a nearby point along the southern road.
859 images were transferred from the drone camera to the Rutgers CRSSA computer server. There, the images were separated into groups by flight mission, and the image groups were concurrently processed on adjacent workstations using Pix4Dmapper software. After GCPs and supplemental manually-added tie points were linked in all images, the group links were merged and the full image set was processed using the merged link set. A Digital Elevation Model and photomosaic were generated.
Conclusions
-Add more GCPs to field for more accurate drone maps
-Calibrate camera -More developed Pix4D
application (malfunctions impaired results)
-Longer battery life for a continuous flight project
-Better field clearing technique-Account for variation in
weather, tide, illumination,and seasonality
Acknowledgements
References
Camera Flight Positions & Image Processing Results
Our goal is to create a 3-dimensional spatial model as a reference for long-term monitoring studies at the New Brunswick River Conservation Area wetland in the city of New Brunswick, NJ. The site includes ~40 acres of wetland, including a tidally-influenced slough and dense vegetative cover of Phragmites australis.
Phragmites australis is a widespread wetland reed that maintains some ecosystem services, including sediment stabilization, but reduces fish habitat and may decrease biodiversity.[1] Phragmites may also increase drainage and oxidation, increasing subsidence.[2] Given climate change-induced rises in storm frequency and water elevations, phragmites wetlands may be a valuable natural mitigator during extreme weather events.[3] Previous research has found that phragmites wetlands “actively resist the deleterious effects of sea-level rise” and that phragmites is “likely to stabilize tidal wetlands because of traits that support higher below-ground productivity than the vegetation they are replacing.”[4] Nonetheless, wetland elevation is a site-sensitive function of the interdependent factors of organic material inputs, sediment deposition, and soil porosity; accumulated phragmites litter may increase elevation, but deprive the wetland of depositional inputs.[5]
In these cases where a high spatial resolution is needed, a small unmanned aircraft, or drone, is a useful platform to map changes in wetlands using structure-from-motion photogrammetry.[6] Drone-based remote sensing has been used to measure phragmites heights[7], create digital surface models[8], and digital terrain models despite dense vegetation cover[9]. However, coastal wetlands surveys may require flexible and rapid deployment of sampling missions[10], and extensive image post-processing.[11,12]
We propose to collect imagery with a drone (operated by the Rutgers-NJ Agricultural Experiment Station’s Office of Research Analytics), and process it into a 3-dimensional model that can be used as a reference for future changes in wetland extent and elevation.
GCP marker with Bad Elf GPS unit
Clearing vegetation for accessibility;Track of pathways cleared and GCP locations
Pix4D with four overlapping flight plans
We would like to thank Lucas Marxen, Dan Farnsworth, Alejandro Ruiz, and Rick
Lathrop for their assistance
[1] Raichel, DL; Able, KW; & Hartman, JM. Estuaries (2003) 26: 511. See also Yuhas, CE; Hartman, JM; & Weis, JS. Urban Habitats (2005) 3:158-191 .[2] Chambers, RM; Meyerson, LA; & Saltonstall, K. (1999) Expansion of Phragmites australis into tidal wetlands of North America. Aquatic Botany 64:261–273. [3] Weis, J. April 3, 2019. “As climate change erodes US coastlines, an invasive plant could become an ally.” The Conversation. https://theconversation.com/as-climate-change-erodes-us-coastlines-an-invasive-plant-could-become-an-ally-111162 Accessed 5 April 2019.[4] Kirwan, ML & Megonigal, J.P. (2013) Tidal wetland stability in the face of human impacts and sea-level rise. Nature 504 (7478):53 .[5] Karstens, S; Jurasinski, G; Glatzel, S; & Buczko, U. (2016) Dynamics of surface elevation and microtopography in different zones of a coastal Phragmites wetland. Ecological Engineering. 94:152-163. [6] Kalacskaa, M; Chmura, G.L; Lucanus, O; Bérubé, D; & Arroyo-Mora, J.P. (2017) Structure from motion will revolutionize analyses of tidal wetland landscapes. Remote Sensing of Environment. Volume 199, 15 Sept, pp.14-24. [7] Meneses, NC; Baier, S.; Reidelstürz, P.; Geist, J.; & Schneider, T. (2018) Modelling heights of sparse aquatic reed (Phragmitesaustralis) using Structure from Motion point clouds derived from Rotary- and Fixed-Wing Unmanned Aerial Vehicle (UAV) data. Limnologica 72, pp.10-21.[8] Samiappan, S; Turnage, G; Hathcock, LA; & Moorhead, R. (2017) Mapping of invasive phragmites (common reed) in Gulf of Mexico coastal wetlands using multispectral imagery and small unmanned aerial systems. International Journal of Remote Sensing, 38:8-10, 2861-2882.[9] Meng, X; Shang, N; Zhang, X; Li, C; Zhao, K; Qiu, X; & Weeks, E. (2017) Photogrammetric UAV Mapping of Terrain under Dense Coastal Vegetation: An Object-Oriented Classification Ensemble Algorithm for Classification and Terrain Correction. RemoteSensing, 9(11), 1187.[10] Doughty, CL & Cavanaugh, K. (2019) Mapping Coastal Wetland Biomass from High Resolution Unmanned Aerial Vehicle (UAV) Imagery. Remote Sensing 11(5):540.[11] Bhatt, P. (2018) Mapping Coastal Wetland and Phragmites on the Hiawatha National Forest Using Unmanned Aerial System (UAS) Imagery: Proof of Concepts. Michigan Technological University, ProQuest Dissertations Publishing. 13421185.[12] Thornton, V. (2018) Determining Tidal Characteristics In a Restored Tidal Wetland Using Unmanned Aerial Vehicles and Derived Data. Virginia Commonwealth University, VCU Scholars Compass Theses and Dissertations.[13] Lai, Jonathan. “Rutgers bans drones on campus.” 4 Apr 2016. Philadelphia Inquirer.[14] Pix4d Blog. “Do more GCPs equal more accurate drone maps?” 5 Nov 2018. https://www.pix4d.com/blog/GCP-accuracy-drone-maps Accessed April 2019.
Locations of: images (red) taken by drone. GCPs and manually-added tie
points (blue) Final mosaic output of entire wetland
Final DEM (digital elevation model) output
of entire wetland
100m
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