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Hi Marc,
can you kindly explain to me when the "Auto" option is effective in the selection of the rings?
In the case of a passive linear array with 24 geophones, 2m spacing, as soon as I activate the Spac button, the image with 20 rings appears without having to activate the Auto option.
Scrolling through the messages window I realize that the software asks questions and gives the answer by definitively accepting the ring for the various openings of the array, always starting from 0m, up to 32m, therefore it takes into consideration new rings (from 38m to 38m, from 40m to 42m, from 42m to 44m).
On the other hand, scrolling through the data of the rings in the Spac toolbox you can see that the minimum and maximum values ​​of each ring are the same and increase by 2 for the following rings (2-2,4-4,6-6 etc.) up to ring 16 ( 32-32) beyond which the min and max values ​​differ by 2 (34-36, 36-38) and then by 4 (38-42, 40-44).
Messages window content:
Relative coordinates with reference at (20.95 0.00).
Checking number of pairs (18> = 6?)
Checking that thickness is at least 20% of the average radius (0 <= 0.4?)
Ring definitively accepted
Starting a new ring from 0 m to 2 m
Checking number of pairs (16> = 6?)
Checking that thickness is at least 20% of the average radius (0 <= 0.8?)
Ring definitively accepted
Starting a new ring from 0 m to 4 m
Checking number of pairs (16> = 6?)
Checking that thickness is at least 20% of the average radius (0 <= 1.2?)
Ring definitively accepted
Starting a new ring from 0 m to 6 m
Checking number of pairs (16> = 6?)
Checking that thickness is at least 20% of the average radius (0 <= 1.6?)
Ring definitively accepted
Starting a new ring from 0 m to 8 m
Checking number of pairs (16> = 6?)
Checking that thickness is at least 20% of the average radius (0 <= 2?)
Ring definitively accepted
Starting a new ring from 0 m to 10 m
Checking number of pairs (15> = 6?)
Checking that thickness is at least 20% of the average radius (0 <= 2.4?)
Ring definitively accepted
Starting a new ring from 0 m to 12 m
Checking number of pairs (13> = 6?)
Checking that thickness is at least 20% of the average radius (0 <= 2.8?)
Ring definitively accepted
Starting a new ring from 0 m to 14 m
Checking number of pairs (12> = 6?)
Checking that thickness is at least 20% of the average radius (0 <= 3.2?)
Ring definitively accepted
Starting a new ring from 0 m to 16 m
Checking number of pairs (12> = 6?)
Checking that thickness is at least 20% of the average radius (0 <= 3.6?)
Ring definitively accepted
Starting a new ring from 0 m to 18 m
Checking number of pairs (11> = 6?)
Checking that thickness is at least 20% of the average radius (0 <= 4?)
Ring definitively accepted
Starting a new ring from 0 m to 20 m
Checking number of pairs (10> = 6?)
Checking that thickness is at least 20% of the average radius (0 <= 4.4?)
Ring definitively accepted
Starting a new ring from 0 m to 22 m
Checking number of pairs (9> = 6?)
Checking that thickness is at least 20% of the average radius (0 <= 4.8?)
Ring definitively accepted
Starting a new ring from 0 m to 24 m
Checking number of pairs (8> = 6?)
Checking that thickness is at least 20% of the average radius (0 <= 5.2?)
Ring definitively accepted
Starting a new ring from 0 m to 26 m
Checking number of pairs (7> = 6?)
Checking that thickness is at least 20% of the average radius (0 <= 5.6?)
Ring definitively accepted
Starting a new ring from 0 m to 28 m
Checking number of pairs (6> = 6?)
Checking that thickness is at least 20% of the average radius (0 <= 6?)
Ring definitively accepted
Starting a new ring from 0 m to 30 m
Checking number of pairs (6> = 6?)
Checking that thickness is at least 20% of the average radius (0 <= 6.4?)
Ring definitively accepted
Starting a new ring from 0 m to 32 m
Checking number of pairs (5> = 6?)
Checking number of pairs (9> = 6?)
Checking that thickness is at least 20% of the average radius (2 <= 7?)
Ring definitively accepted
Starting a new ring from 36 m to 36 m
Checking number of pairs (7> = 6?)
Checking that thickness is at least 20% of the average radius (2 <= 7.4?)
Ring definitively accepted
Starting a new ring from 38 m to 38 m
Checking number of pairs (5> = 6?)
Checking number of pairs (7> = 6?)
Checking that thickness is at least 20% of the average radius (4 <= 8?)
Ring definitively accepted
Starting a new ring from 40 m to 42 m
Checking number of pairs (6> = 6?)
Checking that thickness is at least 20% of the average radius (4 <= 8.4?)
Ring definitively accepted
Starting a new ring from 42 m to 44 m
Checking overlaps among the 20 rings (max overlap = 50%

What other array geometries can the "Auto" option be used with and when is it convenient to do so?

Thanks and best regards
Luigi

Hi Luigi,

The "Auto" option and the first set of rings found when opening the tool are the same processing.
The autoRing function is defined in "SPACRing.cpp", it is based on a few simple rules. It is a loop over all pairs sorted by increasing distance. Pairs are added to the current ring while their distance is the same as the max radius of the ring. In other words, if the ring thickness is not affected by the new pair.

If the inclusion of the new pair affects the ring thickness, more tests are performed. For a non linear array, the maximum angular step is checked (round 180 deg). If it is less than 40 deg, the first station pairs of the ring are progressively removed to make the ring thinner but keeping the maximum angular step lower than 40 deg. The number of pairs must be greater or equal to 6. The relative ring thickness must be lower or equal to 0.2. If so, the ring is accepted and message "Ring definitively accepted" is issued. All pairs with the distance equal to the minimum radius of the ring are removed from the current ring and the process is repeated.

At the end, to avoid many overlapping ring, overlapping rings with more than 50% are filtered out.

In principle, it works for 2D and linear arrays. In the latest implementation the distribution of rings looks better than yours. There are probably some bugs fixed. Here is the obtained list of rings:
The last column is the number of pairs per ring. In this case, it correctly decreases from 23 to 6 (36 m). For higher distances, two distances must be joined to reach a minimum of 6 pairs. Over 42 m, there are less than 6 pairs.

The next release under Windows for 3.5.0 is not expected before a few weeks. Meanwhile, you can save the above table in a .ring file and load it in SPAC tool.

Best regards,

Marc

Thanks Marc,
now everything is clearer