Name: NCC_Pugwash_Estuary_Eelgrass_Aerial_Images_2014

Display Field: Site

Type: Feature Layer

Geometry Type: esriGeometryPolygon

Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>This layer represents the eelgrass distribution in the Pugwash Estuary as of August, 2014. The methods and analysis leading to the creation of this layer is as follows:</SPAN></P><P><SPAN STYLE="font-weight:bold;">Methods:</SPAN></P><P><SPAN>Aerial imagery was taken August 20, 2014, between the hours of 12:50pm-2pm where low tide was 0.6m at 12:44pm, by a Cessna high winged aircraft equipped with a vertical photo hole in the belly. A Canon 1DX - 18MP camera with a 35mm lens was used for the true colour photos and a specially modified IR version of the Canon 5DMarkI 13MP camera with a 35mm lens was used for the infrared photos. The area was flown in parallel lines, at 2000ft for the color imagery and at 4000ft for the IR imagery.</SPAN></P><P><SPAN>Roughly 1500 JPEG images were taken for the color map, of which roughly 1000 were used to assemble the final large map. The IR images map was made from about 700 images. Agisoft's Photoscan and Photoshop CS5 softwares were used to assemble the map, using both TIFFs and JPEG file formats depending on the size of the map. The map was assembled into strips, which joined one at a time to form a larger piece. Some manual editing was needed to join some of the images. </SPAN></P><P><SPAN>To compile individual images into one large image of the estuary, the resolution was reduced slightly (~10-15%) due to the limitations in file formatting (JPEGS can't be any more then 1.0GB and TIFFS can't be any more then 4.0GB in size). That means individual files and smaller compiled images have slightly more detail then the image of the entire estuary.</SPAN></P><P><SPAN STYLE="font-weight:bold;">Analysis: </SPAN></P><P><SPAN>The analysis was completed by NCC staff using ArcGIS 10.1. First, the image was georeferenced to ESRI basemap imagery using a third-order polynomial and the cubic convolution resampling technique was employed in the georeferencing process. </SPAN></P><P><SPAN>Due to initial issues converting rasters to vector formats, the initial imagery was resampled using cubic convolution into a 5m pixel size. Then, using the Image Classification Tool, a maximum likelihood classification was run to classify the imagery based on the pixel value. The dense and sparse classes were extracted from the raster and converted to a vector format (shapefile). Polygons less than 25m² were deleted, and polygons within 15m were aggregated (clumped together. Finally, manual editing was required to edit the classified areas since the pixel classification had issues differentiating between water and eelgrass, qualifying sparse beds as they were a combination of multiple bare sediment and eelgrass pixels. Fifty-one ground control points were taken August 21, 2014 (the day after aerial imagery was flown) and compared to the final eelgrass delineations for an accuracy assessment.</SPAN></P><P><SPAN STYLE="font-weight:bold;">Results:</SPAN></P><P><SPAN>The eelgrass meadows in the Pugwash estuary comprise ~54% of the estuary with an area of 282ha. The eelgrass is primarily distributed within the basin of the Pugwash estuary, though there are beds extending up into the Pugwash River (south of the main basin). When compared to the ground reference points, there was an 82% accuracy in eelgrass classifications.</SPAN></P></DIV></DIV></DIV>

Service Item Id: 334a2367ceb546c39f21bb1c5411231b

Copyright Text: Nature Conservancy of Canada

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Fields:

• OBJECTID ( type: esriFieldTypeOID, alias: OBJECTID )
• Shape ( type: esriFieldTypeGeometry, alias: Shape )
• Site ( type: esriFieldTypeString, alias: Site, length: 50 )
• Year ( type: esriFieldTypeString, alias: Year, length: 50 )
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