Data were collected from March to April 2020. The area is relatively plain and proximal to the coastal line in the southern part of Penajam Paser Utara regency in East Kalimantan province. Measurements were completed on a transect that is perpendicular to the existing utilities with 60-meter interval per line. We used a GPR system with a 100MHz frequency of AKULA 9000-Geoscanner for collecting data at the sites.
The
system GPR collect the data with 150 ns time length and the sampling rate of 512
sample per trace, 45 scans rate, and 32 scans range. Low cut filter of 125 MHz
and high cut filter 25 MHz were used to collect data. GPR profiles were acquired with
the common-offset technique in continuous time mode, and stacking up to three
traces and background of 20. The relative dielectric permittivity (RDP) 11 of unsorted soil was
chosen for data acquisition. The position of the selected location
(coordinates of latitude and longitude) were marked and recorded using Global
Positioning. A
total of 106 GPR reflection profiles with the length varies between 30m-120m that
corresponding to 7 km of linear extension. All data were acquired using the
same acquisition parameters.
The main
steps used in the basic processing routine were: time-zero correction, dewow,
AGC, band-pass filtering, running average filter, background removal filter, deconvolution
and time–depth conversion.
All the 106 GPR data sections along the unloading facility
have been processed and interpreted for the position of the pipeline. The
interpreted section all presenting in the attachments-1.
The following staging we are using for interpretation of GPR
data:
(1)
All 106 GPR sections have been
processed using the basic processing steps as explained in the previous section.
(2)
Interpret pipe position and
depth in the GPR processed section, and the result for example showing like the
following section.
Cross-section within model area