How Satellite Images Provide Total Phosphorus Monitoring White ...

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Total Phosphorus Water Monitoring UsingSatellite ImageryFigure 1: BWSI Total Phosphorus Processed Image Example, Lake WashingtonBWSI calculated the average concentrationof Total Phosphorus in the 9x9 pixel field atthe location of each field data point(Nearest Neighbor Average) and comparedthem to the field data reported concentration.These data points, all measured within24-hours of overpass were then analyzedusing regression analysis. Both the R 2 andR 2 adjusted values are shown above. Forthis evaluation, the R 2 adjusted value wasreported to be 0.59, which indicates thereis a good degree of correlation despite thefact that BWSI had no control over the fielddata collection methods or accuracy of thefield results. This analysis can show that using the BWSI processed images for Phosphorus screening is certainlya data collection option for both historical and future monitoring efforts. The next evaluation shows how the datacorrelation improves when the time of field sample collection and satellite overpass are closer together.Blue Water Satellite, Inc.PAGE 5
Total Phosphorus Water Monitoring UsingSatellite ImageryCORRELATION WITHIN 1 AND 0.5 HOURSOF OVERPASSThis evaluation allowed BWSI to correlate processed data withfield data gathered when the time of sample collection wasrecorded. Available data from surface water bodies referencedabove was used where the following information was reported:• Total Phosphorus Concentrations (ppm)• Time of sample collection• Coordinates of sample location on the water bodyEven though BWSI is evaluating data collected by otherorganizations and the exact collections methods are unknown,a good indication of how the BWSI data can predict the averageconcentrations in a given location in a lake is to use those datapoints that have a collection time recorded close to the time ofsatellite overpass. The data variability should decrease whenthe difference between the field collection time and time ofsatellite overpass decreases.This relationship is demonstrated in the following evaluation.Using data points from the same three lakes referenced above, atotal of 28 data points were available for which the sampleswere reportedly collected within 1.0 hours of overpass and 14data points had reportedly been collected within 0.5 hours ofthe recorded satellite overpass time from the BWSI processedimages. The range in Total Phosphorus Concentrations for thefield data was 0.007 ppm to 0.107 ppm.BWSI had processed Total Phosphorus Water images for thethree lakes referenced above for the dates on which thecorresponding field data was collected. The BWSI processeddata was averaged for each of the 9x9 pixel grids where eachcorresponding data location was centered. Therefore, the BWSIconcentration from the processed image represented an area of90m x 90m. An example of the processed image for LakeChamplain is shown below in Figure 3.Figure 3. Lake Champlain-USA. Natural Color Image (Left), BWSI Total Phosphorus Water Processed Image (Right).Blue Water Satellite, Inc.PAGE 6
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