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I'm plotting some geolocations (lon, lat) of tweets collected using the Stream API with a 7mi. radius. The picture below shows two maps of the same data, but using different alpha/transparency for each observation.

Looking at the map on the left, I noticed that the geolocations follow mostly a sort of imaginary "grid" with specific nodes. Anyone could help me to understand why this pattern surfaces?

enter image description here

Of course, I do have roundings in the coordinates, eg:

"loc: 42.7388,13.1798"         "loc: 42.6252,13.2948"         "loc: 42.6008,13.293"          "loc: 42.73,13.2028"          
"loc: 42.66918468,13.27893702"

but my question is why these roundings occur since I assumed that the Twitter API would guarantee the same level of precision?

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    It could either be the precision of the tweeter's GPS or other location data, or the twitter client only sending to a certain precision. Can you see what client sent the tweet? Is the grid 1/10 of a degree? Or is it a precise number of metres? Hmmmm – Spacedman Jan 19 '18 at 18:23
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    It doesn't seem like Twitter provides only four decimal points, at least not a while back: gis.stackexchange.com/questions/119923/… – underdark Jan 19 '18 at 19:23
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    It seems based on the version of the software that is used, and on the device: help.twitter.com/en/safety-and-security/tweet-location-settings – JGH Jan 19 '18 at 19:26
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    they are being aggregated using a fishnet tessellation, or something similar. – atxgis Jan 19 '18 at 20:26
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    @atxgis any idea about who does the aggregation? Is the device that cannot communicate with a level of accuracy that is high enough? – Dambo Jan 19 '18 at 21:52
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+50

I have looked at tweets to some extent. But not in your area.

But I suspect this is down to two types of tweets.

Actual tweets that fall into two categories. The correct geolocation with specific precision (see the tweets in the urban area), and town level geolocation (see the stacks in the urban area).

Then you have automated tweets. These are the ones that fall on the grids. For example for the data I am capturing:

enter image description here

The tweet highlighted above the black lines are all from an automated flood alert system.

I would check your data first to see if there are any trends.

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    You mean those are tweets from the same system but from different locations? What would the purpose be? I'll take a look and get back to you, I remember thinking about what you mentioned, but I actually have different levels of rounding (not just either 4 or 9 decimals). That suggests rounded geolocations are not necessarily produced from discrete geotags. – Dambo Nov 13 '18 at 17:10
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    I'm suggesting there is a twitter bot that is tweeting the gridded locations. For example in my tweets its a flood alert bot. These are geolocated flood alerts, but the locations fall along a grid. – HeikkiVesanto Nov 13 '18 at 18:06
  • Yes, I got what you mean. I was just wondering whatfor... – Dambo Nov 14 '18 at 21:48
  • If I was creating a bot I would probably do it to 4 decimal places as well. Otherwise you are suggesting a level of accuracy that just cannot be attained if you are not on the ground. 4 digits is down to around 10 meters, gis.stackexchange.com/questions/8650/…. – HeikkiVesanto Nov 14 '18 at 22:00
  • Again, I get that, but what I am trying to say is: why would you need a bot that mimics different locations for tweeting flooded-related content. What can the goal possibly be? – Dambo Nov 14 '18 at 23:15

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