I heard that some 3rd party tool can resize your map to 480 x 480 tiles (which is 61440 x 61440 distance units). I don't believe terrain itself could take much space, but lets try to apply some theory here.
Lets take a single tile and think what possible data can it contain.
- Terrain type (Grass, Rough Dirt, etc): well, there might be over 256 terrain types (or maybe not), but lets assume pessimistic case and increase the limit to 65536: 2 bytes.
- Terrain type variation: cap of 256 is surely enough: 1 byte.
- Height: I cannot see much precision of this value (at least not in WE) si I assume float type: 4 bytes (it could be an integer though, making it 2 bytes).
- Cliff level: 15 possible values, ergo, it fits in 4 bits, so maybe it shares a byte with some other value, lets hold on this one.
- Cliff type: on each map, it has maximum two possibilities (so lets hold on 1 bit).
- Cliff variety: tested on Lordaeron it had at least 3 variations (2 'convex' and 1 'concave') (at least 2 bits).
- Blight: a tile can be blighted or not (1 bit).
- Boundary: the same as with bligth (1 bit).
- Water: 1 bit (shallow water is the same as deep water, but with different cliff level).
- Ramp: 1 bit.
- Shadow map: I have observed that generated shadows have approxmiately the precision of the smallest grid in WE. 16 such little squares cover a tile. 16 times 2 possibilities (shaded or not) equals 32 (5 bits).
- Lets sum up all the bits not joint into bytes yet: 4 + 1 + 2 + 1 + 1 + 1 + 1 + 5 = 16 bits = exactly 2 bytes.
Ok, now lets add all the bytes: 2 + 1 + 4 + 2 = 9 bytes per tile. Lets look at yor map. You say its size is 10240 x 8960 (80 x 70 tiles), so I inferred from this statement, that you provided size of playable area (values of entire map must be multiple of 32). Minimal full map area would be 96 x 96 = 9216 tiles. having 9 bytes per tile it gives exactly
81 KB, which is not that bad ^^.
Assuming that the max possible dimensions are 480 x 480 it would give 2025 KB, a bit under 2 MB (1.977), which hurts a bit in comparison with B.net 4 MB cap. You can't go more than 576 KB in World Editor though.
Note 1: I assumed pessimistic cases wherever I could, so it probably could occupy less disk-space. Also take the possibility of compression into consideration.
Note 2: All this is entirely my personal theory, so I do not guarantee its propriety.
