Reliability test of Inverse Distance Weighting (IDW) method by linier limits

The Inverse Distance Weighting (IDW) is a multipoint interpolation method used in predicting the missing data as well as that can be used to count the average regional rain fall. According to Prasasti, it is necessary to include more data in order to obtain more significant interpolation result. So, to improve the accuracy of IDW method interpolation result, it is conducted by adding auxiliary points linearly between adjacent stations which then are called as IDW linier method. The reliability test is conducted by comparing the calculation results of linier IDW method by exact surface field and mathematic equation as well as conducted the application reliability test in the field, namely by comparing the calculation results with the observed data. Results of the application reliability test in exact field by mathematic equation of X+Y+Z/10 = 12 by using 3-5 rain stations, show that there is an average accuracy increase of IDW linear method of 2.21% from the original IDW method. Meanwhile, the reliability test in the field, Sidoarjo Regency and Mojokerto Regency show that the linear IDW method has an average accuracy increase of 5.13%. This accuracy increase is caused by the addition of some information and increasing close of information to the expected points, namely the auxiliary points.