Pemodelan dan estimasi sumberdaya nikel laterit menggunakan metode ordinary kriging di PT Vale Indonesia Tbk, Sorowako, Kecamatan Nuha Kabupaten Luwu Timur, Provinsi Sulawesi Selatan = Modeling and estimation of nickel laterite resources using ordinary kriging method at PT Vale Indonesia Tbk, Sorowako, Nuha District, East Luwu Regency, South Sulawesi Province