This howitzer can fire all standard NATO 155mm ammunition. It has a minimum range of 780m and can fire high-explosive incendiary/armour-piercing (HEIAP) ammunition to a range of up to 42km, and rocket-assisted projectile (RAP) to a range of 50km.
So the range is 42km and 50km. When we project this on Snake Island this is what we get.
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But in that area you have something very important: The Romanian border, a NATO country.
So when we cut of the Romanian part of this cone, and we follow the coastline, we get something like this.
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This is an area full of swamps and rivers, and very hard to place heavy artillery. You need a steady ground to fire (and adjust fire). So that limits the options.
A bridge was build right before 07 MAR between two Island next to the "GeoLocated" Island.
There is also a house with what seems a possible dock near that Island.
8/
On 25 FEB the Island was overrun, so the building of this -what seems to be- a bridge started soon after the capture of Snake Island. It seems likely that Ukraine was planning all along to shell Snake Island from the coastline.
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Conclusion:
It is highly likely that Ukraine indeed used 2S22 Bohdana 155 howitzers to shell Snake Island.
Not only did we geolocate a firing location, Snake Island is also within range for the HEIAP ammunition.
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It's also possible that the fact that they fired from an area this close to a NATO country played an important role in the assessment from Russia to not engage it and because of that, they had to withdraw from Snake Island.
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Why is Snake Island so important and the loss of it a huge blow for Russia? (Ref. Zoka's reaction)
Because it's a "strategically and tactically important rock" to say it with the words of @CovertShores
"11 rockets were let out by Russian occupiers across Mykolaiv and Ochakiv, Ukraine. 3 people died, including a 6-year-old girl. Another 3-month-old baby is in a coma now."
"On June 28, at 4 am #Russia's occupiers fired missiles at residential buildings in #Ochakiv, #Mykolayiv region. 3 civilians confirmed dead, including 6-year-old child."