Posts Tagged ‘heat map’

New City Landscapes – Interactive Tweetography Maps (UrbanTick)

Wednesday, June 30th, 2010

screen-shot-2010-06-30-at-13502-am

[Editor's note: Series of maps showing twitter tweet density in New York, London, Paris and Munich (some but not all tweets are tagged with geographic coordinates) with hypsometric tints, contours, and placenames (with some literary license). A little more refined than those San Francisco crime maps floating around earlier this month. Thanks Andy!]

Republished from @UrbanTick

Over the past few months we have been harvesting geospatial data from Twitter with the aim of creating a series of new city maps based on Twitter data. Via a radius of 30km around New York, London, Paris, Munich we have collated the number of Tweets and created our New City Landscape Maps.

Continue reading at UrbanTick . . .

Density (heat) map of world-wide photos on Panoramio

Tuesday, May 25th, 2010

550_touristyness

[Editor's note: Neat idea, but not as detailed (street level) as the Flickr effort, post up next.]

Republished from Info is Beautiful.

Great places-to-avoid heatmap using distribution of photos on Panoramio. Nice idea! By BlueMoon.ee

World map color-coded by level of touristiness, based on analysis of photos on Panoramio. Yellow indicates high touristiness, red medium touristiness, and blue low touristiness. Areas having no Panoramio photos at all are grey.

Continue to view the map . . .

Density Mapping in Google Maps with HeatMapAPI (GeoChalkboard)

Monday, April 27th, 2009

[Editor's note: Heat maps are a useful way to qualitatively represent densely clustered point locations on a map. This post from GeoChalkboard walks thru how to create using the Google Maps API and the HeatMap API.]

Republished from GeoChalkboard, there on March 11, 2009.

In the GIS world heat maps are a graphical representation of point data on a map through the use of colors that indicate the density of some variable such as crime incidents or traffic accidents.  Heat maps let users quickly visualize the density of locations. Being able to understand the density of point locations makes it much easier to see patterns in your data, especially when using colors. In this post we’re going to examine the HeatMapAPI, a JavaScript API for creating heat maps in Google Maps.


(Above) 2009 Starbucks Store Closures

Introduction
HeatMapAPI can be used over the Internet or as a .NET DLL that runs in a local environment and allows you to integrate heat map images into Google Maps or other GIS systems.  In this post we’re going to use HeatMapAPI to visualize the density of recent Starbucks store closures.  In a recent statement, Starbucks announced the closure of 600+ stores in the United States due to economic conditions.

Continue reading at GeoChalkboard . . .

GBIF data heat maps – Heat maps over Google Maps for Flash (Biodivertido)

Wednesday, September 3rd, 2008

[Editor's note: Fascinating proof-of-concept for how to create and display heat-maps in Google Maps for Flash/Flex AS3 using PHP back-end for calculation and Flash for front-end. More information for using Google Maps in Flash CS3 download and reference and tutorial. Similar to some nifty work Zach Johnson is working up at Universal Mind for spatialkey.com.]

Reprinted from Biodivertido.

Maps like everything else seems to be trendy. And nowadays the sexy thing in mapping is the creation of Heat Maps. The best way to understand what they are is to see them:

You can also take a look at this post from one of my favorite blogs on what is and what is not a heat map.
Well for long time I wanted to give it a try and yesterday I had the time to experiment a bit. The idea was to display GBIF available data as a Heat Map over Google Maps. Here you have an screenshot for Quercus ilex:
And if you want to try for yourself here it is (some usability issue, the search box is on the bottom right corner):
So how does it work? It was actually easier than I expected:
1) Get the data: I am using the so called “Density tables” from GBIF. You can access them through GBIF web services API at http://es.mirror.gbif.org/ws/rest/density . For example in a query like this one for Quercus ilex (of course you need to get the taxonconceptkey from a previous request to the services): 
This works fine but has some problems. The first one is that GBIF goes down almost every evening. Tim can maybe explain why. Thats why I am using the spanish mirror (look at the url) and I recommend you to do the same.
Second problem is the verbosity of the XML schema being used. For downloading the Animalia, well thats the biggest concept you can get probably, the result is 14.1 MB of XML. And thats just to get a list of cellIds (if anybody is interested we can post details about CellIds) with counts on them, exactly an array of 34,871 numbers. Even worst is handling them on a web client like this one, parsing such a huge xml output kills the browser. The GBIF webservices API deserve its own blog post I would say together with Tim.
But what is new is that I have supercow powers on GBIF :D I am working for GBIF right now and have access to a test database. In a testing environment I developed a little server app that publish the same density service but using theAMF protocol. I used AMFPHP for this if anybody is interested. There are two good things about using AMF: The output now is around 150 KB for the same thing and AMF is natively supported by Flash so there is no need to be parsed it goes straight into memory as AS3 Objects.
2) Create a Het Map from the data: Once the data is on the client I make use of a Class from Jordi Boggiano called HeatMap.as that creates Sprites as the result. In my case I decided to create a Spring, think like an Image, of 1 pixel per cellId creating a 360×180 pixel image (cellId is equivalent to a 1 degree box).
3) Overlay the image on Google Maps: When you have the Sprite, or even earlier but thats too many details, what you do is overlaying in Google Maps for Flash using a GroundOverlay object that takes care of the reprojection and adapting it to the map. The GroundOverlay is explained in the doc as a way to overlay images but it accepts actually any Sprite.
Done! (almost)
4) Ok, there are some problems: Yes, it is not perfect, these are the pending issues:
  • The GroundOverlay seems to not be reprojecting correctly the Sprite I generate and in the very north and south everything is not correctly overlayed.
  • The resolution of the Heat Map is a little bit poor, bu actually represent the quality of the data we have. Some interpolation could be done to make it look nicer.
  • The colours of the Heat Map do not fit well with the actual Google Maps layers. When there is small data then you can not see it almost.
I still dont feel confident with the code to release it yet. I hope I can work a little bit more on it so that i can be proud, but if you desperately need it let me know.
Just another notice. Yesterday Universal Mind released a preview of a new product: Spatial Key. I am always impressed with what this people does and follow the blogs from their developers (like this one and this one). They are kind of my RIA and web GIS heroes. The new product they have released actually look very much like what I wanted to do in Biodiversity Atlas for data anlysis. It lets people explore geographically and temporally huge datasets. Tim suggested me to contact them and I will do. Nevertheless it is great to have such a great tool available to get ideas on interaction design. Good job Universal Mind, you really rock.
We want to see your comments!
Update: 
Some people asked for different quality settings on the heat map. I have modified the application so that you get now a set of controls to define different quality and drawing options. By default the app tries to figure out depending on the number of occurrences, but maybe thats not the best, depends on how the data is dsitributed. In a final product I think I would NOT provide this functionality to the user, too much for my taste. You know, less is more.