Thunderhead Explorer

Shapefiles are still today the ubiquitous way to share and exchange geospatial data. I’ve been getting a lot of requests lately from BigData Hadoop users to read shapefiles directly off HDFS, I mean after all, the 3rd V (variety) should allow me to do that. Since the format of shapefiles was developed by Esri , there was always an "uneasiness" in me as an Esri employee in using third party open source tools ( geotools and JTS ) to read these shapefiles when we have just released on Github our geometry API . In addition, I always thought that these powerful libraries were too heavy for my needs, when I just wanted to plow through a shapefile in a map or reduce phase in a job. So, I decide to write my own simple java implementation that for now just reads points and polygons.  This 20% implementation should for now cover my 80% usage. I know that there exist a lot of java implementations on the net that read the shp and dbf format, but I wanted one that is tailored to by ...

In this post, I will demo how to load a local shapefile from your hard drive, and overlay it on an map whose base layer is derived from a remote ArcGIS server. Using the Flash Player 10 FileReference API, this task is fairly easy. However, I did not want the user to be prompted for each imported file as a shapefile is composed of a .shp file holding the geometry and a .dbf file holding the attributes. So, the idea is to zip the shp and dbf and load the zip, and then let the application unzip the content and parse the shp and dbf entries. The application is using the Flex API for AGS and makes use of two wonderful as3 library; the shp library from Edwin van Rijkom , and a zip library from David Chang . In this application, I created a custom geometry to take advantage of the coordinate array format in the shapefile reducing the impedance and taking advantage of the "compression". Well, this not truly compressed - this an array of x,y,x,y,etc... rather than an array of MapP...

Not sure if some of you have see the 3D in-door routing application that I did for the ESRI 2009 User Conference. I used Papervision3D for this app, and was a lot of fun to develop. A couple of weeks before the conference, I decided to implement the same app on an iPhone using Obj-C. Being a newbie in the latter, I ramped up quickly on the language (got quickly over my hang ups on bracket, and kinda like the language :-). I started to look at the 3D built-in engine that uses a derivative of OpenGL and thought that I will not have the time to get this up and running. So I started to look for simpler alternatives. I read Keith Peters' most excellent AdvancED ActionScript 3.0 Animation book and used his A* implementation for client side routing application with barriers. check it out here . The next chapter in the book is all about isometric projection. This is exactly what I needed, an isometric view of the CDCC floors and rooms with a small twist, where the user can rotate th...

Due to the ubiquitous nature of geographical data in shapefile format, I want to embed a shapefile in a flex application and display it as a layer in a map. This work is borrowed and modified from Edwin van Rijkom . The modifications include the generation of Geometry subclasses based on the Flex API for ArcGIS Server . So, to get started, I created a ShpLayer class that is a subclass of GraphicsLayer . I initialized this layer's symbol property with an instance of ShpSymbol which is my own custom symbol (more on this later). This way, I do not have to assign a symbol to each added Graphic instance. Internally, when a graphic is rendered, and that graphic has a null symbol property, it inherits its parent's symbol property value. This is an easy way to globally change the symbology of a graphic layer, without having to explicitly iterate through all its children :-) The fact that I've created my own custom symbol is yet another demonstration of the extensibility of ...

Doug McCune (one of my all time Flex heroes) contributed heavily to SpatialKey , which looks and works great. Got to see it last week at 360|Flex in San Jose. I've been wanting to do something similar, but in 3D! Dabbled a bit with Papervision3D , but wanted to get into it, and that was the perfect opportunity. The idea that I had was to read a country shapefile , and thematically map all the cities in that country based on some attribute. And do all that on the client using Flex. I did a little bit of research, and here is a list of sites that "inspired" me: http://blog.papervision3d.org/ http://code.google.com/p/vanrijkom-flashlibs/ http://www.darronschall.com/weblog/archives/000273.cfm http://www.seld.be/ http://blog.zupko.info/?p=150 And here is a snapshot of the result: You can download the source code of the application from here . And you can see a sample demo here .

ESRI shapefiles are fairly ubiquitous. That is why I keep getting requests like this “Hey, I would like to render my local shapefiles on top the AWX map, can I do that ?” And I reply “Sure...but !” - Remember the security sandbox of the flash player; 1 - you can only communicate with the server that hosts the swf, or with a host that has a crossdomain.xml file, and 2 - there is no way that you can access your local disk drive directly - So, let’s turn these two restrictions into assets :-) I’m luck enough to run on a Mac, which comes with Apache Web Server built in. So, if I place a crossdomain.xml file at the base url of my local server, then I can access my local shapefiles. Cool eh ? Next, found this AS3 library that can read the shp and dbf file given a ByteArray instance. Here is a code snippet that I used on a project to overlay the continents shapes on top of the map. private function onCreationComplete( event : FlexEvent ) : void { var urlStream : URLStream = new URLStream(...