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IKONOS imagery with four multispectral bands similar to Landsat TM bands 1-4 and high spatial resolution (4-m multispectral and 1-m panchromatic) is potentially well suited for aquatic plant surveys in lakes and wetlands. To explore the capabilities of IKONOS imagery for aquatic plant surveys, we acquired a September 1, 2001 IKONOS image for Swan Lake in Nicollet County, Minnesota, USA. Swan Lake is a large (over 9000 acres) type 4 wetland with an abundance of aquatic vegetation. The image below displays the false color composite of raw data over the study area and shows distinct differences throughout Swan Lake that are largely due to variations in aquatic vegetation. |
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| Due to the size of Swan Lake and the abundance of aquatic plants the collection of reference data would be very difficult without the aid of modern technology. For this study we took advantage of Global Positioning System (GPS) technology and advanced GPS tracking software on Imagine 8.5. Field reference data were collected using the GPS tracking software on a Fujitsu pen computer. Different types of aquatic vegetation were identified in the field and located directly on the IKONOS image using the field computer. The images below show the Fujitsu pen computer being used on Swan Lake and a screenshot of the computer display. |
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| Being able to accurately identify location on the image while in the field was especially useful on this large wetland. Having the image available quickly after its acquisition for use in reference data collection was a big advantage in field sampling since unique areas with different spectral radiometric response could be identified on the image and targeted for field identification. For this preliminary assessment, emergent vegetation was targeted. However, the abundance of thick submerged vegetation appearing at the surface was also noted. The images below show the lakescape of Swan Lake. |
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| Preliminary classification of a pan-sharpened multispectral IKONOS image was able to provide us with an early map identifying different aquatic vegetation groups throughout the image. With further research, additional field reference data, and processing we expect to identify more specific aquatic plant types. Future plans also include research into appropriate accuracy assessments techniques. This preliminary study has indicated that the use of IKONOS imagery for aquatic plant surveys is promising. The high spatial resolution of the IKONOS imagery enables the assessment of aquatic vegetation variation within lakes and wetlands. The image below shows our preliminary Aquatic Vegetation Map displayed over the panchromatic image of Swan Lake. |
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