This research is conducted to assess the accuracy of spline interpolation methods to predict and model the surface water pH of Pulau Tuba, Langkawi, Kedah, Malaysia. In-situ sampling activities using pH-meter and Geographic Positioning Systems (GPS) were carried out during high tides and at noon in November 2018. The development of spatial models were constructed using the Regularized and Tension spline methods. Then, validation of models was carried out to compare the observed and predicted values of pH using correlation analysis, regression analysis, and error analysis. The accuracy of the developed map was calculated using the overall accuracy equation. The research found that the regularized spline method had more accuracy in estimating surface water pH variability than the tension spline method. The Pearson correlation coefficient (r), Coefficient of determination (R2), Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) were reported at 0.896, 0.803, 0.0265 and 0.0344 for the regularized spline method, respectively. The developed spatial model was then transformed into a map by adding map elements such as legend, title, north arrow, and scales for effective visualization. The developed map has an accuracy of 87.50%. The surface water pH was found at the range of 7-8. The low reading of pH is expected due to the addition of rainwater that lowered the pH of the coastal water of Pulau Tuba, Langkawi, Kedah. The research outcomes would benefit the government and non-government agencies to monitor the coastal and ocean acidification and the development of strategic policies and rules to reduce the impact of anthropogenic activities and climate change for this area.
Kamaruddin S. A., Ahmad Nasir N. A. H., Syafiqah Rahim N., Shuhaime N., Hashim M. A., Suhail Khazali A., Aziz K. N. A. & Roslani M. A., 2021. A comparative accuracy of regularized and tension spline methods to estimate and model the surface water pH of Pulau Tuba, Langkawi, Kedah. Science Letters 15(2): 116-134. Article.
