Display Blurred/ Deidentified map For the Public

[aarontitus]

Original author: v...@aarontitus.net (January 14, 2013 02:09:40)

The home page should be a map of the most recent incident. Icons whose geolocation has been blurred to ~400m are accessible, but the InfoBox must be empty.

This functionality is already built into the system, but broke when we implemented the icon grouping feature.

Original issue: http://code.google.com/p/sandy-disaster-recovery/issues/detail?id=148

[aarontitus]

From v...@aarontitus.net on January 22, 2013 02:28:00 We should probably use a cached version of the map for unauthenticated users. That way the website can handle a spike from media coverage.

Changing to critical because it is important for visitors to see what the tool is supposed to do.

[aarontitus]

From joshua.eric.turcotte on January 23, 2013 02:36:57 While the organization registration form circa #138 seems like low hanging fruit (with the possibility that I misunderstand some parent issues, like #135), I may tackle this next just as a framework familiarization exercise. In my own SDK, I have the redirect disabled, and have spent this evening analyzing the difference between /map while authenticated and not;

Do we have a technique in mind for blurred geolocation... perhaps the rounding of the LAT/LON I noticed in one of the handlers? Maybe that's already done-ish.

I see that there is some mention of caching already among the files, so I shall study those as well during my next evening session.

[aarontitus]

From rostovp...@gmail.com on January 23, 2013 02:50:24 Yep, this was working before, but got broken by recent caching changes. The caching just needs to be fixed for this map to work.

Jeremy

[aarontitus]

From v...@aarontitus.net on January 23, 2013 03:36:42 The current technique to blur geolocation is to round the lat/lon. However, this approach produces a gridding effect in highly populated/hard hit areas like the Rockaways, Union Beach, etc. Essentially, there can be dozens of work orders stacked right on top of one another, and only the top one is accessible.

To avoid the gridding effect, the new approach is to create a second lat/lon for each record. The second lat/lon is created by taking the existing lat/lon and adding a random decimal between +0.001798 and -0.001798 to both the lat and lon. This will create a new random lat/lon blurred to 400m.

Then use that new blurred lat/lon whenever the point is displayed on an unauthenticated map.

Is that clear? -Aaron

[aarontitus]

From rostovp...@gmail.com on January 23, 2013 16:51:30 Make sure to set the blurred lat/lng in the database, rather than generating the lat/lng every time the page is displayed. Otherwise, an attacker could average subsequent results and determine the location of a given house.

Jeremy

[aarontitus]

From v...@aarontitus.net on January 23, 2013 20:24:49 Yes. Agreed. Not to mention the fact that re-calculating a lat/lon each time would put an unnecessary burden on the server. The Blurred lat/lon should be calculated one time (or rather, each time the lat/lon is entered/changed), and inserted into the database alongside the real lat/lon.

[aarontitus]

From joshua.eric.turcotte on January 23, 2013 22:27:32 Makes sense to me;

[aarontitus]

From joshua.eric.turcotte on January 24, 2013 02:01:04 Here; try these; the no-auth /map still is redirecting for now, but when it is up (assuming this patch is a go) (i'll poke at THAT another if not solved this coming saturday at the meet up), it will blur and save/cache any sites created previous to this patch. Depending on how staggered the load of old sites is, that may make for a mild delay on first viewing as all that math is done... but once done, it's done and done. Tested out within my SDK without complaint.

[aarontitus]

From joshua.eric.turcotte on January 24, 2013 02:02:17 Oh, and I tried to design it so that one could pass in alternative blurring radii, if so desired; it defaults to 400 if unspecified.

[aarontitus]

From v...@aarontitus.net on March 05, 2013 22:06:30 If an unauthenticated user visits [root] should display the map for the most recent Incident. If an unauthenticated user visits [root]/, then forwards to an unauthenticated public map for that incident.

The unauthenticated public map should display the following options (Taken from #162):

• Join/Login
• Help
• About
• Blog
• Social Media Links
• Volunteer (See #164). Note: Note: "Volunteer" changes to "Volunteers" for authenticated users, because authenticated users are more likely to look for volunteers.

[aarontitus]

From v...@aarontitus.net on March 14, 2013 09:43:00 Andy, Your current implementation on the public map is great. The current system rounds the lat/lon to ~400m, creating a gridded effect. This effect is apparent on the Bartow-Gordon GA Tornado event. Next, we will need to create Now we just need to introduce the blurred lat/lon feature. I think I came up with a method to do that, but I can't find the notes at the moment.

[aarontitus]

From cpw...@gmail.com on March 14, 2013 10:55:34 Was it: when setting site.lat and site.lon, also set site.blurred_lat and site.blurred_lon, using a new random number each time ?

[aarontitus]

From v...@aarontitus.net on March 14, 2013 13:51:34 Ahh... found it on comment 4 above: Yes. Set site.blurred_lat and site.blurred_lon by adding a random decimal between +0.001798 and -0.001798 to site.lat and site.lon. This will create a new random lat/lon blurred to 400m.