The web is full of different solutions for compressing things, but some of you have probably already done this and found a really good ratio compression scheme that fits what I'm asking about.

I've got a load of entites, (4-7k) that live on a grid (1024x1024), and I need to persist them to a savegame which gets sent across the network to keep the save safe. I need to compress it. I'm compressing the entities in the world already, ones that have been affected cost a few bytes, but the but for the ones that don't have any changes, all I'm left with is the coords. There are only a few that need the fatter compression, but at the numbers I'm looking at, those "unchanged entity" coords add up to a lot of data when storing as 20 bit structs. This is too much for sending over the network regularly as part of a save.

I've had some ideas on how to compress the data, but they might be crap. I don't know.

I can't easily regenerate the set so thought someone who wanted to compress consumables might know the name of a good solution for sparse bitset compression. The bits are clumped around different areas of the grid, so I feel that something that leverages spatial coherence might do well.

Any leads would be highly appreciated.

"The fact that an opinion has been widely held is no evidence whatever that it is not utterly absurd." - Bertrand Russell