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Public Lab Research note

Introducing Leaflet Blurred Location Display Library .

by sagarpreet | April 02, 2019 08:02 02 Apr 08:02 | #18933 | #18933

Hello everyone ,

Public Lab takes utmost care in making sure that the location of a person is exposed to the extend he/she wants . Hence we here at Public Lab are working on giving people the power to safely share their location on the web .

I am happy to announce two new libraries that we are working for the past few weeks that helps in achieving this vision of ours .

In this post , i wish to introduce these new Public Lab open source software projects on Location Privacy .

Leaflet Blurred Location Display :

Leaflet-blurred-location-display (LBLD) is an extension of leaflet-blurred-location (LBL) and does the following:

  • Cleverly displays your location, keeping your privacy settings in mind .
  • Color code the markers on the map according to the precision .
  • Shows heat map to analyze number of people at different rectangles of the grid .
  • Fetches data from remote API or you may pass array of coordinates directly into LBLD API .

The demo is live :

1.) Shows Public Lab users location :


2.) Shows how some locations (markers) are not shown at different zoom levels :


So at Lower zoom levels , irrespective of the precision of coordinates you shared - your marker is visible on map . But as you zoom in to higher zoom levels , lower precision markers are removed .

To see details on how to use the LBLD library in your project , jump over to our github page : https://github.com/publiclab/leaflet-blurred-location-display


1.) Lower the precision , Greater the privacy :

The red markers corresponds to coordinates [23.1 , 77.1] , [20.1 , 76.1] having precision of 1 . At lower zoom level 5**** , these red markers are visible on map . image description

But as you zoom in to level 6 , these red markers are removed from the map whereas other high precision markers are still visible .
image description

2.) Color Coding of the markers :

image description

According to the precision of the coordinates , different colors are given to the markers .

Precision = 0 , Blue colored markers .

Precision = 1 , Red colored markers .

Precision = 2 , Orange colored markers .

Precision = 3 , Green colored markers .

Precision = 4 , Black colored markers .

Precision = 5 , Grey colored markers .

Precision >= 6 , Yellow colored markers .

Also clicking the markers shows a pop-up telling the precision :
image description

3.) Heat map :

Greater the markers in a region , Darker the color .

We wanted to give an easy visualization power , so we implemented this grid heat map .

image description

The default color of grid is : #F3F0C0

If number of markers are in range [1,10] , the color is : #FFA500

If number of markers are in range [11,15] , the color is : #faff05

If number of markers are in range [16,25] , the color is : #FF6347

If number of markers are in range [26,35] , the color is : #FF4500

If number of markers are in range [36,45] , the color is : #FF0000

If number of markers are greater than 45 , the color is :#8B0000

NOTE : Clicking on each rectangle shows the pop-up showing number of markers in that rectangle .

4.) Custom API and JSON parser :

You can pass your own API link to fetch data and show it on the map . Also you need to pass a JSON parser function to parse your API . See our Github page to know more details !

Blurred-Location library :

A JavaScript library to help manage variable location privacy through a "blurred location" model .

This library is an independent module which gives many mathematical functions that one can use on any map (not necessary Leaflet map!) . The library is thoroughly tested using Jasmine framework .

Jump over to the github page for more details of each mathematical function : https://github.com/publiclab/blurred-location

The npm link is : https://www.npmjs.com/package/blurred-location

If you have any suggestions or any doubts regarding the use of this library , kindly open an issue here .

I personally thanks @warren for mentoring me and giving all these awesome ideas .

Sagarpreet Chadha

Thank you :)


Awesome work @sagarpreet @warren 🎉 💯

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This is so great, @sagarpreet!!!! 🎉 you've done a fantastic job and these libraries are really coming to life!

For others -- these will soon start to be featured on the website here! For example on the https://publiclab.org/people page! 👍 🎉

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Hi @liz , @stevie ,

I and @warren are working on integrating this library to /people page . I am hoping to get your opinion on :

1.) What should be the grid color coding we should use ?

2.) What should be the color of marker ?

It would be great if you post your answer here as well : https://github.com/publiclab/plots2/pull/5358#issuecomment-479473790 .

Thank you 😃 !

Is this a question? Click here to post it to the Questions page.

You can check these live demos here :

Reply to this comment...

Hi @sagarpreet these demos look amazing! To your questions above,

1) The gridline color in orange, with highlighted gridsquare in red looks great to me. A vibrant contrast with a blue-green planet. Open to other ideas if anyone has any!

2) The colors of the markers might work as a spectrum, maybe something from http://colorbrewer2.org

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