Just to add to this discussion, since I’ve noticed similar behavior and also have been testing iRobot / Roborock vacuums. I think there’s two issues at play …
From what I can tell, the map is aligned to the “base station”. This creates the diagonal, the bot uses this starting point to align the mapping grid. If you happen to be lucky to have walls which run relatively straight to eachother, you’ll get a straight map. If your house is even slightly crooked, like mine is, you’ll get really odd jagged walls and misaligned.
The bot uses the base station alignment to map out the vacuuming path. Slightly diagonal/crooked base station, and you get diagonal/odd vacuuming paths (I tested this one myself, the vacuum did 45deg paths by offsetting the base 45deg, lol).
This leads to another issue, the base station is flimsy and prone to rotating when the bot docks. I’ve noticed on numerous occasions that the bot has parked slightly off rotation to the 180deg it should be. If it does this little by little, I speculate that positioning gets thrown off (if there’s not enough to identify the position) and that causes the map to wig out / flip because it’s identifying a starting position elsewhere on the map. I’ve seen some users post this issue with their maps and you can clearly tell it’s been flipped, the bot didn’t vacuum part of the house because it was no longer orientating itself to the map correctly, so what it thought was an access point was now a wall.
These methods are contrary to what iRobot and Robovac both do for their mapping. Both:
- Align the longest point (straightest estimated wall) of the mapped area to a fixed grid. This creates straight walls.
- Determine a vacuuming pattern on a room by room basis, based on the longest portion.
- Have weighted docks, so they don’t rotate. Although dock rotation doesn’t matter, since they align the map to the grid.
- I believe they both apply some form of smoothing algorithm to the display map, with iRobot’s being really aggressive (but it does make for a pretty map) in that regard.
Hopefully they fix this up.
Some screenshots for comparison.
RoboRock (note, this is aligned 180deg to the others):