Thursday, April 2, 2009

Boston Showcases Solar Power Potential with ESRI's Web GIS

Here's a podcast on the Solar Boston web mapping application I did as a guest on the ESRI Speaker Series.

Wednesday, April 1, 2009

Flex Spatial Filter - Update

I'd like to quickly revisit the Flex Spatial Flickr post as I've made some enhancements to address some bugs and other undesireable behaviors.

The biggest improvement you'll see is in the behavior of the popup for the selected photo -- particularly for photos located near the edges of the map display. I have implemented a modified version of the InfoPopup used in the the Sample Flex Viewer. This popup is a component which 'floats' over the map to display the selected photo. I am still using an InfoSymbol to display the photo thumbnails in the graphics layer -- but wasnt happy with the mouseover behaviors here. I think this is a much better approach.

I have also made some minor adjustments to the photo search results. I am filtering out photos that are missing attributes -- like title and dimensions -- that are needed by the application. Ive also adjusted the search bounding box so that only photos within the map extent are returned.

Im much happier with this now. Onto something new next week...

Tuesday, March 24, 2009

Flex Spatial Flickr

Some of you may be aware that the ArcGIS API for Microsoft Silverlight/WPF is now available as a public Beta. This was released on the eve of the 2009 ESRI Developer Summit. I am among the many who unfortunately couldn't attend this year due to the current economic climate.

The Silverlight API looks rather promising - very similar in form and function to the Flex API. The ArcGIS Server Development Team provided this Spatial Flickr sample in the Code Gallery. This is a pretty slick mashup for sure.

As an advocate of Flex, this sample inspired me to develop a similar sample using the Flex API. Here is the live application as well as the application source.

This sample uses the ActionScript 3.0 API for Flickr available on Google Code. This photo search method of this API was missing needed 'geo' functionality -- so I extended it accordingly.

This sample application will retrieve Flickr photos for the current map extent. Photo tags are optional, but will be included in the search if provided. The search results are added to the map as well as provided in a data panel. The map graphics and data panel respond to mouse focus and click events. My sample doesn't have all the animation provided in the Silverlight sample -- althought it could be extended to include such. There are a few noteable quirks with the map graphics particularly those near the edges of the map window. Perhaps I shall revisit this sometime.

So, Silverlight or Flex? Time will certainly tell...

Saturday, March 21, 2009

Easy MVC Pattern for ESRI Flex API

I've gotten off to kind of a slow start here with my blogging. It seems this space will in fact be more of a dribble than a torrent.

In the year that I have been developing with the ESRI Flex API I have come to learn the importance and value of using a good architectural design pattern. I am a big fan of the Model-View-Controller (MVC) pattern and use it in most if not all of my projects. Using the pattern has saved my ass on numerous occassions -- and neglecting to use it has come back to bite me.

Although there are a number of popular Flex MVC frameworks available (eg. Cairngorm, pureMVC, mate, Model-Glue, among others) --these can be overkill for simple web mapping applications -- particularly for beginners. Ive found that many folks have chosen to avoid these what can be larger more complicated frameworks in favor of their own home-grown MVC solutions. I believe that can be a good option -- particularly for smaller projects.

Once such pattern is the EasyMVC pattern by Tom Bray. Be sure to check out the recorded seminar for all the details. This is the MVC pattern that I use most frequently. In this post I have provided the ESRI Flex API MapSwitcher sample using this pattern.

Here is the application in action as well as the application source.

I am certainly not advocating this as the best MVC pattern out there... but I believe its a good place to start place for beginners and small projects. In future posts I will likely use either this pattern -- or the pattern used by the ESRI Sample Flex Viewer (for posts in that context).

In the meantime, happy Flexing and welcome to MVC.

Wednesday, February 18, 2009


Hello and welcome to blog. My name is Greg Knight. I am currently employed with the Boston Redevelopment Authority as Sr GIS Application Developer. I am interested in most things geoSpatial. I spend most of my days at the BRA with ArcGIS Server -- particularly the Flex API -- of which I have grown very fond. This blog will likely be a 'dribble' of my experiences building web applications with ArcGIS Server and complementary technologies such as web services, xml, sql server, etc.  If things go well, I may have to rebrand as geoTorrent! :)

Hope you enjoy.