According to Shearer and Ashmore (1979), resistivity detector is a kind of instrument which is used on archeological site ground reconnaissance. However, Shearer and Ashmore (1979) stated that resistivity detector was not widely used in the past because it more time consuming and less successful than magnetometer. Nowadays resistivity detector method is starting to be applied commonly in archeological ground reconnaissance due to the advancing of the new technique. The technique is called ERT or electrical resistivity tomography. ERT Survey took place in the peak of Gunungsari Hill. Gunungsari Hill administratively was located in Salam District, near Muntilan City. Salam District is a part of Magelang Regency, Central Java Province. This survey’s main purpose was to discover the missing part of the temple ruin that was suspected below the temple area’s ground.
This research consists of several steps such as litterateur study and field observation, ERT survey, ERT data processing, and then ERT data interpretation and buried objects identification. ERT survey used Wenner Schlumberger array, an electrode configuration which has good vertical and horizontal coverage but it also has vertical and horizontal distortion. Processing ERT data in this research was carried out by X2IPI and Res2DInv software. Data interpretation was conducted by considering about Gunungsari Hill archeology, culture, history, geomorphology, geology, hydrogeology, geophysical characteristic, and also distortion effect of used array.
ERT survey can provide a subsurface map that contains information about both of horizontal and vertical location of buried objects. ERT survey is also easy to be conducted and also it has good precision if the interpreter knew much about the survey area characteristics. ERT survey result on Gunungsari Hill provides information that there are 11 buried andesitic materials those are strongly suspected as buried temple parts. They are located from just few centimeters to a half mater below the surface