摘要：The purpose of this research is to evaluate the precision of the Inverse Distance Weighted (IDW) to estimate and map the coastal water pH for the sustainability of Pulau Tuba, Langkawi, Kedah. 30 sampling points have been set up during two sampling activities in November 2018. The pH meter has been calibrated and lowered to 1 meter below the water surface to measure the reading of pH. The development of the spatial model was developed using the spatial analyst tool available in ArcGIS Software. Several types of statistical analyses were carried to compare the observed and predicted value of pHs such as correlation analysis, regression analysis, and error analysis. Accuracy assessment was carried later after the transformation of a spatial model into a surface map. The research found that the IDW method successfully interpolated the pH readings. The research found that there is a strong positive correlation between the observed and predicted values. For error analysis, Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) were recorded at 0.033 and 0.044, respectively. After the transformation of the spatial model to the surface map, the accuracy of the map is recorded at 81.25%. The map produced can be used by residents and local government for social and economic development and protection of biodiversity at the coastal water of Pulau Tuba, Langkawi, Kedah.
