Comprehensive Look at the Geoweb (Part 3 and 4)

The the story continues... I have been off and on the buzzword "Geoweb" for several years. I am now back on it so I set out to try and take a real look at the Geoweb, at least for the sake of academics. The term is bantered about a bunch and we all have our own take on what it really is. My goal was to try to comprehensively define the geoweb based on well documented patterns, models and architectures that currently exist within the web (part 1 and part 2 of this 4 part series) as well as from a purely organic perspective. Here are the slides that were used for this discussion. I can post my lectures as well if anyone is interested.

Comprehensive Overview of the Geoweb

View more presentations from Government/CU Denver.

In summary, I came up with what I think is a very nice analogy in an attempt to somehow concisely define the Geoweb. I use the analog of an ecosystem defined as:

“An ecosystem is a natural unit consisting of all plants, animals and micro-organisms (biotic factors) in an area functioning together with all of the physical (abiotic) factors of the environment. Ecosystems can be permanent or temporary. An ecosystem is a unit of interdependent organisms which share the same habitat. Ecosystems usually form a number of food webs…” (Ecosystem, 2009)

Using this, we can begin to crosswalk components of the geoweb to the notion of an ecosystem. The geoweb as a unit of something finite, is composed of biotic and abiotic factions. Biotic factors including users, participants, perceptions (top-down vs. bottom-up), change and usability. Abiotic factors such as architectures, standards, formats, specs, platforms, etc... There are a number of relationships that exist between these factors, each with their own microprocesses but all interdependent in varying ways. Finally, portions of the the geoweb are permanent and some are temporary, depending on all of the factors (and their associated relationships) listed above.

If nothing else, have a look at the references cited section at the end of the slides. It includes alot of great materials from many leaders in the community that are worthwhile having a look at.

Ecosystem. (2009, August 26). In Wikipedia, The Free Encyclopedia. Retrieved 17:10, August 26, 2009, from http://en.wikipedia.org/w/index.php?title=Ecosystem&oldid=310197121

ArcGIS Server Sample Flex Viewer: TwitterFeedWidget

I have been thinking about how Twitter could be used to enhance the capabilities/user experience of a web mapping system and came op with some decent stories. The first would be providing users with access to a feed dedicated to the application which contains information about it including updates, news, changes, downtimes, etc. The second would be users who wish to perform searches of Twitter content that may be related to the map and eventually, overlaying geolocated Tweets onto the map. These (and the fact that I just wanted to poke around the Twitter API) gave me enough of an excuse to start messing with the Twitter API. I ended up with a simple little widget that allows users to search for tweets within a specified geographic location, in this case, a circle. Nothing earth shattering but still maybe somewhat useful. Before giving you some of the nuts and bolts of this, I want to be sure and reference the materials I used:

• Flex Cookbook Entry: Display a Twitter Feed
  
• Flex Cookbook Entry: Accessing Resources CrossDomain
• Free Twitter Icons
• Custom Draw with Circle Tool
• Distance Calculations website
• Flex XML Syndication Tools
• Flex CoreLib Utility
  

Some Details on how it works.
It is really pretty simple. The user is able to draw a circle on the map and any tweets that originated from within that location based on the Twitter user's location property are returned as an ATOM Feed. The processes uses the Twitter API geocode parameter where a lat, long and radius of a circle are needed. The widget obtains the lat, long, and radius values from the circle tool. I added a coordinate transformation function to the Circle Tool component to convert the distance units (radius of the circle) to miles from decimal degrees. I used the Great Circle Distance Formula. The ATOM feed is parsed using the Flex XMLSyndication package and is validated using the Flex CoreLib Utility Package (see links above).

Proxy Server
As with any application making cross-domain asynchronous data requests, a proxy server is needed to "fool" the browser security settings. Flex has a nice framework for bypassing this. If the feed host contains a crossdomain.xml file that allows cross-domain access, you are good to go. However, Twitter locks this down (Twitter crossdomain.xml). I have included a proxy server implemented in Java within the package. It is NOT PRODUCTION quality but will get you started. There are other implementations that are easier out there. Have a look at the resources I sited for some other examples.

Known Issues and Limitations
Simply put, there are several limitations with this that make it, lets say, less than production quality. I hope to rectify these soon. These include:

• I haven't tested the feed results very well. The widget catches feeds that are empty which is good but the way I did this is kind of sloppy. I won't go into it here but if you have questions, I can elaborate.
• The coordinate transformation for the distance units (radius conversion from DD to miles) I am using is very rough but good enough for this use.
• It doesn't play very nicely with the map action and map navigation state of the Sample Flex Viewer (SFV). Given that the draw circle component wasn't designed for use with the SFV, it isn't integrated very well with the event driven model the SFV uses. Not to say it isn't a nice component because it is. Using it in the Sample Flex Viewer is just a bit of a stretch. There are alot of issues with this but from a use perspective, users have to keep clicking on the draw circle tool after each use and then state defaults back to the default map navigation (pan). Another problem is if the user trys to change the map action or map navigation state (by selecting another component that does so), during the middle of component use, bad things happen. One of the reasons for this is that I didn't want to make changes to the core by adding custom events, etc. However, I am hopeful that I can improve this without making changes to the core and will look into it.
• Improvement can be made to the tweet results listing (links to profile, user timeline, etc...).
  
• Alot of other testing needs to occur as well. Just running out of time right now.
  

AIR/Flex vs. Silverlight Debate

Now that the ArcGIS Server development platform has finally come of age, many are asking: which platform do I use? There are a number a criteria that enter into this equation and I think others have done a good job of defining these so I will not be discussing them here. The intent of this post is simply to provide you with some of the resources I have found that evaluate at least the 2 RIA platforms ESRI is now providing: Flex and Silverlight. There is alot of chatter/bashing going on and it is often hard to sift through some of the biases so the following are the most resent/unbiased postings I could find. For what its worth, I think they are both great and good for one another. The harder they compete, the better off we all are. Heck, I hope we even start discussing JavaFX in the near future.

The Battle for the RIA Throne: Flex vs. Silverlight
Flash vs. Silverlight: What Suits Your Needs Best?
Video: Air/Flex Silverlight Debate: MS and Adobe evangelists go head to head.

Initial ArcGIS Server Flex API Map Viewer Rollout

The USGS Energy Program is beginning to rollout their latest online mapping application using ArcGIS Server and the Flex API. It is pretty vanilla right now but includes some nice features under the hood including:

1. URL parameter interface
2. Live Map classification widget
3. Separate Map Navigation
4. US Geologic Energy Resources Summary Widget
A whole set of nice features are in the oven including:

1. Metadata and static legend integration
2. Access to over 100 different services
3. Custom widgets based on content type.