Since you didn't zero they don't mean anything.
Ground Probe
"PHASE ANGLE" is the measured difference between the transmitted signal and the signal received from the target. Different materials have different characteristics (resistivity, reflectivity, conductivity, density, etc) which affect the signal that is returned from that specific target. It is this difference between the transmitted and returned signal (phase angle) that is measured by.
The detector only reports VDIs converted from positive phase angles (0 to 180 degrees). The negative angles aren't valid assuming that the machine is calibrated correctly. In the ground probe screen, you may see negative angles if you are holding the coil in the air so there is no real signal coming in - just noise, or you haven't zeroed it first. Once you zero the machine and lower it to the ground, or read your target, your phase angles should come in between 0 and +180 (as with anything there will be exceptions - ground conditions, noise, what have you). A ferrite bead will come in very close to 180 degrees (-95 VDI) which is close to where most normal ground comes in and pure conductors will come in around 0 degrees (+95 VDI). Salt water (wet beach or fields with lots of fertilizer and wet) comes in close to 90 degrees (0 VDI) Approximate numbers.
Ground should fall between 0 and 180 degrees. In air, when you zero the detector, you will see phases of both positive and negative values - those are just noise and don't pay attention to them. If you are getting a negative phase for any of the frequencies when you lower the loop to the ground however, you probably have an overload problem. Most ground that we see is 178 (-94) to 165 degrees except salt which falls close to 90 degrees (VDI 0).
The VDI reading is converted from the ground phase normalized to standard VDI units. It's either going to be from the strongest signal if the detector is running best data, or the average of the two strongest signals if correlate is selected. If you have ground coming in at -94(VDI) with a signal strength of 2% and another ground coming in at -91 with a signal strength of 7%, it would seem to me that the ground coming in at -91 is more mineralized even though it is a less negative VDI. A signal strength of the ground as follows 0 to 10% weak, 10% to 20% Moderate and 20% and up to be strong. The lower the mineralization, the slower one should sweep - which may mean a lower filter should be selected. The phase tells you composition (between purely ferrous and purely salt), while the signal strength tells you the concentration (more mineralized).
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