Remote Sensing of Wetlands Josh Kauffman Brief Outline Why study wetlands Remote Sensing benefits drawbacks The Landsat program Aerial Image Spectroscopy The future http commons wikimedia org wiki File Wetlan ds Cape May New Jersey jpg Why Study Wetlands Wetlands are ecologically vital areas which provide habitat for diverse organisms from plants to fish to birds Wetlands also filter out pollutants from rivers and streams used by people They also act as buffer zones protecting the inland from storms and flooding http walton ifas ufl edu images hurricane Benefits of Studying Wetlands Remotely http www calistogatroop18 org photos 20061014 20Anderson 20Marsh 20Hike 20353 jpg Salt marshes and other habitat are difficult or impossible to traverse on foot Remote sensors greatly reduce the need for painstaking groundwork NASA s Landsat satellites and airplanes fitted first with cameras then Multi Spectral Scanners MSS and later Thematic Mappers or TM and Enhanced Thematic Mappers ETM with LiDAR can capture vegetation even down to species in some cases These technologies can also identify areas of water leaf greenness and exposed soil Time series can be used to identify habitat loss soil erosion and water inundation The Landsat Program In 1972 the Landsat I satellite launched into a sun synchronous 900 kilometer high orbit with a 99 2 degree inclination for near global coverage a period of 103 minutes and a repeat pattern every 18 days Landsat II and later III took over while following the same orbit parameters until the launch of Landsat IV which packed newer technology 1 http upload wikimedia org wik ipedia en 4 41 Landsat1 jpg Equipped with Multispectral Scanner Systems these satellites were best for very large wetland studies due to low resolution and shaky geometric precision 2 Multispectral Scanning Systems The MSS systems on the Landsat satellites are passive sensors that measure radiation perpendicular to the orbital path via a rotating mirror which passes light reflected off the Earth into 24 sensors 6 for each band The four bands measured are the 500 600 600 700 700 800 and the 800 1000 nanometer spectra Red Green and Blue are bands 7 5 and 4 respectively With a pixel size of 68m x 83m the MSS system is only really useful for large scale land use coverage 2 http www geology iastate edu gcp satellite images im age36 gif The Landsat Program cont d http www geog ucsb edu jeff 115a history land sat45 gif The introduction of Landsat IV in 1982 and Landsat V in brought about a new technology called Thematic Mapping Greatly increased resolution allowed scientists to map and study wetlands ecology as never before These two satellites were launched into a sun synchronous 705 km 98 2 degree of inclination with a 99 minute period and repeat coverage every 16 days Unfortunately the U S Government privatized satellites at this time inflating data prices and causing scientists to stop collecting data This led to a loss of very valuable satellite imagery because the data went unstored during this period 3 Thematic Mapping Thematic Mapping on Landsat IV and V operated in a whisk broom method with a mirror oscillating left and right Secondary mirrors fill in the gaps left by this method 5 Data is collected across 7 bands Bands 1 4 are the visible spectrum band 5 can detect leaf soil moisture Band 6 is an infrared thermal imager and band 7 detects moisture content as well http geology com novarupta maps landsatnovarupta region large jpg The TM instrument has allowed scientists to reach 30 meter resolution which in wetlands study is very important though greater resolution is always better This is 2 5 times better than the MSS resolution TM also has better geometric stability Landsat 7 and ETM Landsat 6 failed during launch in 1993 and in 1995 Landsat 7 took over In the same orbit as Landsat 4 and 5 this new satellite carried a payload that included a very precise radiometric calibration unit an onboard data collector and the Enhanced Thematic Mapper with a panchromatic band achieving 15 meter resolution multispectral 30 meter resolution 6 http landsat gsfc nasa gov i mages lg jpg l7satellite jpg Enhanced Thematic Mapping Enhanced thematic mapping is better for wetlands evaluation than TM because of the greater spacial resolution better instrument calibration and higher geometric fidelity thanks to GPS systems Both technologies are used to study aspects of wetlands such as vegetation cover high water mark habitat loss fragmentation and water quality The biggest use of these technologies is studying land use and change over time Side by side comparison of TM left and ETM right images of harvest time in Nangrong Thailand From http www cpc unc edu projects nan grong data spatial data remote sen sing satellite imagery 7 IKONOS Satellite The IKONOS 2 commercial satellite has brought spacebased spectral imaging resolution down to just 3 2 meters 0 82 m panchromatic This provides an incredible opportunity to gather data not just on large tracts of wetland estuarine habitat but also within habitat variations and features 681 kilometer 98 2 degree of inclination orbit and a repeat time of around 4 days 8 http borrowedearth files wordpress com 2 008 05 mangrove0459sm jpg Can be used to classify mangrove communities at a very high resolution by assigning unique spectral identities to vegetation cover and use that information to predictively analyze unexplored or inaccessible mangrove forests Airborne Visible InfraRed Imaging Spectrometer http aviris jpl nasa gov html aviris overvi ew html One study successfully used the AVIRIS system to produce a vegetation map of the Everglades down to individual species with a roughly 66 accuracy very good at this point in time 10 The latest in remote sensing of wetlands is the use of AVIRIS and similar systems These consist of a spectrometer array attached to an airplane flown at extremely high altitudes NASA flies this system on a U 2 plane at 20 000 meters 9 The technology essentially a plane mounted version of the thematic mapper of the Landsat satellites Though with 224 simultaneous bands covering 400 2500 nanometers 9 Gets great resolution which varies with height above ground More predictive of community composition than ETM CAO Systems The Carnegie Airborne Observatory has developed a system like AVIRIS but also incorporates a LiDAR to map beautifully at resolutions of 0 1 to 4 meters depending on the research With up to 288 channels in the visible and near