GeoExt Layer Tree: Showing BaseLayers and Overlay Layer

I was looking for GeoExt's tree example for my project, and I found official tutorials are kind of hard to understand for the GeoExt beginners. On Googleing through the internet, I found nice and easy way of creating tree  structure menu using GeoExt BaseLayer and Overlay layer tree.

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Spatial Developer must keep in your shelf : Book Review

One of my client’s requirements was to create and open source geospatial DBMS to hold utilities and city shape files. As looking through the internet, I found PostGIS is an open source software program that adds support for geographic objects to the PostgreSQL object-relational database.  As project reference, I choose PostGIS in Action, as project accomplished successfully I realized  my judgment was excellent.

PostGIS in Action is a very comprehensive introduction to PostGIS for developers of all levels of experience. Basically it is split into 3 parts:

Part 1- Nice and slow startup with PostGIS. You can skip this section if you have prior knowledge about any kinds of spatial databases and geometry data types.

Part 2- Put PostGIS in work. It contains technical details on proximity analysis, geocoding addresses, manipulating polygons and lines, and scaling and rotating geometries as well as efficient queries and how to tune your database and
selection of appropriate indexes and keys for your data.

Part 3- Use of PostGIS with other tools and frameworks. It describes manage raster datasets in PostGIS with PostGIS raster module, development of Web applications using PostGIS.

The Book will provide the much needed skills in building a spatial database, Application Server, Desktop GIS and Cartographic map renderer, Map tile server and Web map component using the following software: PostGIS/PostgreSQL, GeoServer, Apache/Tomcat, uDIG, Openjump, QGIS, GRASS GIS and Openlayers.

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Interactive Obesity and Rural Health Map

An interactive maps shows the influences of landscapes in rural health using ExtJs,GeoExt,Openlayers,Geoserver,PHP,Jquery, JavaScript, and other opensource tools.
Check it out

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Interactive West Nile virus incidence mapping using OpenGeo tools, Google APIs, & HTML5

The Geographic Information Science Center of Excellence at South Dakota State University developed a web based West Nile virus (WNV) mapping application using Geosever, Openlayers, PostGIS,GeoWebCache, Jquery, Google visualization APIs, and, other open source technologies. This application allows users to pan, and zoom to visualize historical WNV patterns while using a slider bar to navigate through time. Users can click on counties to see -county level time-series graphs, case counts, and total population. The application also supports changing choropleth transparencies, choropleth classifications, and map backgrounds.

Methods:

A. OpenGeo tools:

i.     Open layers

ii.    Geoserver

iii.   WebGeoCache

iv.   PostGIS

B. Google APIs

i.       Google Maps API

ii.      Google Charting API

C.      HTML5

These are frequently refereed to as HTML5 technologies.

Javascript

HTML Canvas

WebGL

CSS3

Other CSS improvements such as flex boxes

Offline Storage

Geolocation

New events such as touch and orientation

Ajax

Websockets

Click here to visit the Application

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An Interactive Visualization using Geoserver & Openlayers

From last couples of week, I have been involving to develop a interactive web interface for West Nile virus incidence dissemination across the conterminous US from 1999-2011.

The image on the right shows one of my accomplishment using
Geoserver,Openlayers,jQuery, PostgreGIS,and Google API. The project is about to launch online, then I will post a complete link of the project to let you guys play around it.

Click to visit: Web application

I am willing to help any one who is stuck with web maps/visualization and also seek constructive criticism on web stuffs.

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How to retrieve WMS GetFeatureInfo from Openlayers & Geoserver

map.events.register('click', map, function (e) {
//alert(map.getExtent().toBBOX());
x1=parseInt(e.xy.x);
y1=parseInt(e.xy.y);
    var url = layerhost
      + "?REQUEST=GetFeatureInfo"
      + "&EXCEPTIONS=application/vnd.ogc.se_xml"
      + "&BBOX=" + map.getExtent().toBBOX()
      + "&X=" + x1
      + "&Y=" + y1
      + "&INFO_FORMAT=text/html"
      + "&QUERY_LAYERS=" + layername
      + "&LAYERS="+layername
      + "&FEATURE_COUNT=50"
      + "&SRS=EPSG:900913"
      + "&STYLES="
      + "&WIDTH=" + map.size.w
      + "&HEIGHT=" + map.size.h;
    window.open(url,
      "getfeatureinfo",
      "location=10,status=10,scrollbars=1,width=600,height=150"
    );
  });

I got  X and Y points due to floating point error while retrieving GetFeatureInfo . In order to prevent those errors I parse e.xy.x and e.xy.y values into integer, and it works for me.

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Choropleth mapping techniques for Web2.0

For my recent project, I have to display county wise time series data of disease pattern in web map for the conterminous United States for 20 years. In addition, I have to use Google maps as base layer and should overlay images on the top of it.  The concept sounds easy, and it was also similar with choropleth or thematic mapping. However, it should be in the Web 2.0.

I tried to figure out what are the possible ways to achieve this, I tried and few of them. Here I am going to share the pros and cons of these methods in a real quick and dirty style.

Choropleth with GFT

1) Google Fusion Tables

Pros:
Easy, No understanding of computer programming needed. Upload small or large data sets from spreadsheets or CSV files. Visualize your data on maps, timelines and charts. Pick who can access your data; hide parts of your data if needed. Merge data from multiple tables.

Cons:
Not much flexible and you can’t tweaks easily according to your needs. 

Choropleth with Cartographer.JS and Google API

2) Cartographer.js and Google API

Pros: It generates choropleth maps directly from database or other standard data handlers. Fast for small area mapping.

Cons:
Understanding of JavaScript is needed. It supports only US (County and State level data). I got performance is worst if we map entire 50 states. I recommend it to use to map few states only. Although cartographer.js's documentation claims browser friendly, it is horrible with IE, works so so with Firefox and chrome. 

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