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Quantifying Change and Error Among Categories: A Method for Relating Difference by Category with Difference Overall

This research presents a method to measure change and error among categories using component intensities. The method separates overall difference into three components: Quantity, Exchange, and Shift. It can be implemented using the diffeR package in R software or the PontiusMatrix Excel file available at www.clarku.edu/~rpontius.

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Quantifying Change and Error Among Categories: A Method for Relating Difference by Category with Difference Overall

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  1. Component intensities to relate difference by category with difference overall Robert Gilmore Pontius Jr Clark University Association of American Geographers 2019 www.clarku.edu/~rpontius rpontius@clarku.edu The United States National Science Foundation’s Division of Environmental Biology supported this work via grant OCE-1637630 for the Plum Island Ecosystems Long Term Ecological Research site. The Edna Bailey Sussman Trust supplied additional funding via a grant entitled “Applying GIS to quantify marsh dynamics in the Plum Island Ecosystems” for Su Ye to classify the remotely sensed data. .

  2. Major Points • I present a method to measure change and error among categories. • The method separates overall difference into three components: Quantity, Exchange and Shift. • You can use the method with the diffeR package in the R software or the PontiusMatrix Excel file from www.clarku.edu/~rpontius Pontius Jr, Robert Gilmore. 2019. Component intensities to relate difference by category with difference overall. International Journal of Applied Earth Observation and Geoinformation 77: 94-99. https://doi.org/10.1016/j.jag.2018.07.024.

  3. Comparison Quantity, Exchange and Shift Components of Difference 1 1 1 2 2 2 3 3 3 Reference 2 2 3 3 1 1 1 1 2 1 2 Category 1 has Quantity gain of 2 pixels, while Categories 2 and 3 each have Quantity loss of 1 pixel. Categories 1 and 2 have Exchange of 2 pixels. Categories 1 and 3 have Exchange of 2 pixels. Categories 2 and 3 have Exchange of 0 pixels. Remaining difference is Shift of 4 pixels, as category 1 transitions less to 2 than 2 transitions to 1, while 1 transitions more to 3 than 3 transitions to 1.

  4. Size and Intensity by category and overall Each difference involves two categories, thus overall component is half of sum of category components. Category 1 has Quantity component more intensive and Shift component less intensive than overall. Category 2 has Quantity component less intensive and Shift component more intensive than overall. Category 3 has Quantity component and Shift components equally intensive as overall components.

  5. Marsh Grasses Spartina Alterniflora Spartina Patens

  6. Losses from 2005 Alterniflora has Quantity loss while other categories have Quantity gain. Exchange between Alterniflora and Patens constitute most of difference. Patens gains from Alterniflora more than Patens loses to Alterniflora, while Patens loses more to Water than Patens gains from Water, thus Patens shifts. Bare loses to Water more than Bare gains from Water, while Bare gains more from Patens than Bare loses to Patens, thus Bare shifts. Linear features are Alterniflora ditches surrounded with Patens, which appear to move south perhaps due to image misregistration. Gains to 2005

  7. Transition matrix from 2005 to 2013

  8. G denotes Quantity gain. L denotes Quantity loss.

  9. Use diffeR package in R or PontiusMatrix41.xlsx,available for free with videos at www.clarku.edu/~rpontius • Pontius Jr, Robert Gilmore and Ali Santacruz. 2014. Quantity, Exchange and Shift Components of Differences in a Square Contingency Table. International Journal of Remote Sensing 35(21): 7543-7554.

  10. Major Points • I present a method to measure change and error among categories. • The method separates overall difference into three components: Quantity, Exchange and Shift. • You can use the method with the diffeR package in the R software or the PontiusMatrix Excel file from www.clarku.edu/~rpontius Pontius Jr, Robert Gilmore. 2019. Component intensities to relate difference by category with difference overall. International Journal of Applied Earth Observation and Geoinformation 77: 94-99. https://doi.org/10.1016/j.jag.2018.07.024.

  11. Preliminary data and modeling suggests that the marshes at Plum Island will survive to the end of the century but with more open water, wider creeks and more Spartinia Alterniflora

  12. Plum Island Ecosystemsin northeastern Massachusetts

  13. Change 1985 1971 1991 1999

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