Am Freitag, 20. November 2015 15:11:40 UTC+1 schrieb Hanno Schlichting:
> Keeping this on the public list - warning: it's a bit of a brain-dump / rant
> :)
>
> I have to admit that the main reason I took a look at the map was from a
> performance / scaling perspective. Abusing the number of data points per grid
> to indicate something, was the only user visible change I could implement in
> a short time. Abusing point density to indicate recency may not be the best
> choice.
>
> Today we have about 400 million grids (100x100 meter areas) as input into the
> mapmaking. The way we generated the map took close to 10 hours each day. I
> was able to speed it up by parallelizing more of it, but it still takes 6
> hours each night.
>
> If we were to use smaller grids, we'd increase the number of grids and the
> processing time. If we'd use 30x30 meter grids, we'd probably end up with
> roughly 5 times as many grids. You can fit 11 smaller grids into one big grid
> (10000 sqm ~= 11 x 900 sqm), but from experience we know that only about half
> of the smaller grids would actually have data points in them (in cities most
> of them have data, on country roads most of them are empty).
>
> This means we'd end up with 2 billion grids and the map would take more than
> 24 hours to generate, which is rather silly.
>
> We are now at a point, where it makes more sense to build maps showing the
> locations of all the cell and wifi networks. WiFi networks also tend to be
> colocated, so our 440 million WiFi networks only result in about 220 million
> locations rounded to 10 meter precision. The 18 million cells almost don't
> matter from a scaling perspective.
>
> 220 million is already lower than the number of grids we have today, with a
> much better precision. For cell networks we'd really want different maps to
> show different carriers and radio standards, so one could look at only AT&T's
> LTE networks or only Deutsche Telekom's GSM networks.
>
> Those kinds of maps would actually tell you whether or not someone collected
> WiFi networks or cell networks from your carrier in a specific place. For the
> purpose of "should I visit this street" these maps would be more useful. The
> datamap we have today only says that someone went to a place and collected at
> least one data point. But it could have been a single cell entry for a GSM
> network of a different carrier and no WiFi data at all.
>
> Unfortunately we don't know how to build these maps at the scale we have. All
> the standard mapping tools will only be performant until about 10000 points
> on desktop browsers and more like 100 to 1000 points on low-cost Android
> phones. Since the target users would be primarily Mozilla Stumbler users, we
> have to aim for low-cost Android phones with screen sizes of ~300x500 pixels
> as the main audience.
>
> The datamap we have is a nice eye-candy and looks cool. It shows the general
> global momentum and reach of the project. But there is no way to tweak it to
> really do the "should I walk over / drive this street" use-case justice. We
> only keep rendering it at fairly high zoom levels, because we can and we
> don't have anything better.
>
> If anyone wants to help and figure out how to build maps of cell or wifi
> networks, we need you :)
>
> Hanno
>
Don't know if this is related to this topic or not. But recently it seems like
older entries dissappeared from the map in the area where I live. Was this by
design as a solution to reduce the amount of data or is this a bug?
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