Data sets included with GSadjust
Several example data sets, both synthetic data and real-world field data, are included with GSadjust. The synthetic data are generated from known station gravity values with random noise, drift, and calibration error added. These data are useful for testing whether different processing methods are capable of recovering the known station gravity values. The field data were collected using different relative and absolute gravity meters. The "true" station gravity values are unknown.
Synthetic data
Five synthetic datasets are provided with GSadjust in the sgp-gsadjust\test_data\synthetic directory. These test datasets include a range of drift types, number of relative-gravity meters, calibration errors, and survey designs. The details of each are shown in the table below. Random error is applied to the synthetic data, which can be used to test whether GSadjust recovers the known station gravity values through network adjustment. The parameters defining these datasets (drift rate, calibration error, observation error) can be modified in the Excel file GSadjust_TestData.xlsx, and the GSadjust input data regenerated. For example, two test datasets could be generated for an expected level of relative-gravity meter precision, and evaluated as to whether the adjustment can resolve the simulated gravity change. Additional test datasets (for example, with tide error) could also be generated from the examples provided.
The synthetic data are simulated as one sample per station. Therefore, when viewed in GSadjust the plots on the
Data tab will only show a single point rather than a time series.
|
Test case
|
Drift
|
Number of relative-gravity meters
|
Calibration error
|
Survey type
|
|
1
|
None
|
1
|
no
|
Loop
|
|
2
|
Linear
|
1
|
no
|
Loop
|
|
3
|
Linear
|
1
|
yes
|
Loop
|
|
4
|
Linear
|
2
|
yes
|
Loop
|
|
5
|
Nonlinear
|
1
|
yes
|
Dense-network
|
Field data
Field data are provided from ZLS Corporation Burris relative-gravity meters and from Scintrex CG-5 and CG-5 relative-gravity meters.
Burris data
These data were collected using two ZLS Corporation Burris meters. Two surveys were carried out, one in December 2017 and one in February 2018. The coordinates have been changed randomly by about 0.15 degree, so if the tide model is updated it will not correspond to the exact study area. There is corresponding absolute-gravity data for this data in the field\Absolute directory. These data are used in the
complete example.
Scintrex CG-5 data
These data were distributed with the original release of PyGrav (Hector and Hinderer, 2016).
Absolute data
These data were collected using a Micro-g Lacoste, Inc. A-10 absolute-gravity meter. Data were collected in conjunction with the relative-gravity data in the Burris directory. Four stations were occupied with the A-10 during each of the relative-gravity surveys. The gradient was measured at each station and is used to transfer the gravity value from the A-10 measurement height (about 71 cm) to the land surface.
