Georegistering Aerial Photographs: Measuring Seagrass

Georegistering Aerial Photographs:

• Measuring Seagrass

• Prop Scarring

Seagrass

• Submerged flowering plant found in shallow marine or estuarine waters

• Provides habitat for many commercially important animals

• Disturbed by brown tide, low water quality, dredging, and propeller scarring

Project Goals:

• Obtain unregistered aerial photograph

• Obtain DOQQ’s

• Use basemap with known coordinate system to register photograph

• Use registered photograph to digitize and measure propscarring

1. Aerial Photograph

• 1:9,600 format

• Warren Pulich Jr., Ph.D.

• International Institute for

• Sustainable Water Resources

• Texas State University

• San Marcos, Texas

• Coastal Bend Bays & Estuaries Program

2. Digital Orthophoto Quarter Quads

• Computer generated image of aerial photograph with features represented in true geographic positions

• Used as base map

• Coordinate system:NAD83
• Projection: UTM

• http://www.tnris.state.tx.us/digital.htm

DOQQ’s: Estes Flats

Texas Coast

Registering Aerial Photos

• Add unregistered aerial photo to basemap

• Use Georeferencing tools to align aerial photo with basemap

• Fit to display
• Add control points
• Choose transformation order

1st Order Polynomial

2nd Order Polynomial

3rd Order Polynomial

Registered Map

Measuring PropScars

• ArcCatalog: Create New Feature Class

• Use editor and sketch tool to trace along each prop scar

• Open attribute table of New Line feature class and sum total length of new lines

Digitized Propeller Scars

Conclusions

• Higher resolution photo needed for measuring smaller scars

• Thanks. Questions?