Twitter can be used for all sorts of things - to keep in touch with your friends (and even those you don't know so well), and to keep abreast of the latest happenings in technology, the arts, what's going on in your community, and much more. One of the capabilities offered by Twitter is their Geo API, which lets developers build geolocation into their tweets and twitter-based applications. Here's an example of leveraging geolocated tweets to learn more about crime using the ArcGIS Explorer Twitter add-in.

Here we've used the add-in's keyword search to find all tweets using the word "burglary" within a 10-mile location of where we've clicked. Any tweet that uses the keyword will be found and placed on our map.

To do this we clicked the add-in's Search tab, entered our keyword and search radius, and used the pointer tool to choose the location for the search on our map.

One of the matches we found was from a specific user source named alexandr_crime. This source uses information from spotcrime.com to generate geolocated tweets of where crimes have been reported. Note that it shows up in our results with a red pushpin. The red pushpin is automatically inserted by the Twitter add-in when the Geo API is used in the tweet. Other posts may still have a location associated with them, but these red pins specifically indicate those coming from an app using the Twitter Geo API.

Knowing this we can now search for all crimes reported from this particular user to get details about crimes in Alexandria, Virginia. Here's our choices in the Twitter add-in:

And here's the results on our map. You can click any pushpin to see the tweet and learn more about the crime.

For more information you can search for other posts about the ArcGIS Explorer Twitter add-in.

Here's a video we found published by GIShistory on YouTube. Produced with ArcGIS Explorer, this animation shows all earthquakes of magnitude 3 or greater in the Southern California area between 1932 and 2008. Data from USGS.

ESRI shares many useful maps and layers on ArcGIS Online that are of interest to ArcGIS Explorer and other ESRI product users. The ArcGIS Explorer team has also shared maps and add-ins on ArcGIS Online, and many users are doing the same. How do you refine your search to more easily find what you're looking for?

Keyword search

By default when you enter a keyword you'll find all matches. Matches start with tags, but include matches in the description. This means all types of shared content by all authors that have made them searchable. So if we enter demographics:

we will find all content types that match the keyword that have been publicly contributed by all authors.

Search by owner

One way you may want to filter your search is by owner. All ESRI content has been authored by the user "esri." If you're looking for ESRI authored content you can add owner:esri to your search:

This search returns a variety of types, some specifically for use in ArcGIS Desktop or Web maps that can't be used directly in ArcGIS Explorer.

Search for a specific type

But if you look underneath the search box, you'll find you can qualify the results further by choosing a type:

By choosing layers, we're choosing a type (layer packages or layer files) that can be used directly in ArcGIS Explorer.

The ArcGIS Explorer team has organized content and tools (add-ins) into a couple of groups specifically for Explorer users. You can search for all arcgis_explorer shared content using a search like shown below:

Or can search for groups instead of content:

There's lots of other permutations - for more information on searching, visit the narrowing your search results ArcGIS Online Help topic.

A new video has been posted on the ESRI YouTube channel that provides an example of social networking and feeds integrated using ArcGIS Explorer to look at the recent Haiti disaster.

The video illustrates how to use ArcGIS Explorer, the Twitter Add-in, and a number of GeoRSS feeds to build a real-time model of the disaster situation in Haiti.

Check out the recent post on the ArcGIS Developer blog to learn more.

The Twitter add-in can be found in the ArcGIS Explorer Labs group on ArcGIS Online.

Anyone that has taken advantage of the 2D capabilities of ArcGIS Explorer is probably used to this view of the Earth:



In this 2D view the world basically ends in eastern Russia, New Zealand and other areas around the 180 degree line.  For some people this is okay, but for others it is a problem because data is cut off, and measurements can’t be made across the Pacific Ocean.

Using an Add-In and a couple lines of code, you can change the central meridian for geographic projections to fit your display requirements.  The map above shows the 2D map in a World Mercator projection with a central meridian of 0 degrees.  The code below was put into the click event of a button Add-In to change the central meridian to 180 degrees:



The first line of code writes the World Mercator projection out as a string value with the updated central meridian.  The string is then used to create a new CoordinateSystem object and then set as the current 2D coordinate system.  The results are an updated central meridian giving you a different perspective on our 2D world:



It is important to note that maps with custom coordinate systems can’t be saved and re-opened, so if you want to make this switch to the central meridian then you need to do it within each map session or have an extension that runs on startup to make the change.

Please see the Explorer SDK documentation for information on how to create a button or extension with the code above.

(Submitted by: Larry Young, ArcGIS Explorer Team)

Layer packages are an excellent way to combine ArcGIS cartography with data to be shared with ArcGIS Explorer users, but how about using Explorer maps and layers in ArcGIS Desktop? We're working on an integrated capability that will be delivered in a future release, but in the meanwhile we discovered a couple of solutions recently posted by the ESRI user community on the ArcScripts and Resource Center sites.

Here's one contributed by Anthony Lopez via ArcScripts. The description states: This script converts ArcGIS Explorer Notes to a single Shapefile and stores the note title and comments as attributes.

And here's another by melvanderwal that's been shared on the .NET community resource center. The description reads: This component library extends ArcGIS Desktop to utilise ArcGIS Explorer v.900 files as data sources. ArcGIS Explorer files (.nmf, .nmc) will be available through ArcCatalog, ArcMap, and ArcScene. The files are displayed as databases, and organised into feature datasets based on coordinate system. Within feature datasets, feature classes can be found representing Point & Target, Line, and Area notes.

Remember that ArcScripts and other community shared solutions are not supported by ESRI, but there's a lot of useful tools that are available, many of which include the source code so you can add your own tweaks. You can visit the ArcGIS Explorer Gallery to find more, and of course we encourage and welcome other additions from the Explorer user community.

As mentioned in previous posts popups are an excellent and easy way to add content to your map.  Popups are found on notes as well as views and can be used to display a variety of information such as text, photos, web sites, videos, and more. 

Using HTML you can display formatted and non-formatted text strings, as well as more advanced things such as images and even graphs.  Suppose I’ve highlighted a section of my map with an area note that overlaps some of my own data or data coming from ArcGIS Online (census information, for example).  You may want to display a summary of that information in the note popup using HTML and a chart API. Here we're using the Google chart API to accomplish that.

The HTML to make this note is relatively simple and looks like this:

In the first line we add the title “Gender” in bold. After adding a blank line we create our chart popup image by calling the Google chart API using the following parameters:

cht – chart type (p3 for pie chart)
chd – chart data (t is for text encoding, followed by the data to be used as percentages)
chs – chart size in pixels
chl – chart labels

Then we add a few more blank lines followed by a similar syntax for charting age.

It can be tedious to enter this information by hand, so you may find it easier to add this type of content via an Add-In.  The Query Demographics sample in the SDK Help demonstrates how to programmatically query census information from ArcGIS Online and create the chart content above.

(Submitted by: Larry Young, ArcGIS Explorer Team)

As we look back on the ArcGIS Explorer blog for this past year we see that we've covered a broad range of topics, including reviews of events, tutorials, and other noteworthy news for Explorer users.

Which were the most popular? They're listed below. Hit counts still keep going up for more recent posts, and for some popular older posts. But here's the summary of the most popular posts as of this morning.

The overall most popular post by a very wide margin was:

Mapping the Arctic using ArcGIS Explorer

In second place was:

Using add-ins from ArcGIS Explorer Labs

Coming in as third most popular was:

System requirements check for ArcGIS Explorer

And the rest of the top 10 in order:

Controlling navigation when you add content

New version now available and what's new

A tutorial for creating good Layer Packages

ArcGIS Explorer at the 2009 Federal User Conference

ArcGIS Explorer at the BPC Plenary Part III

ArcGIS Explorer at the 2009 User Conference Plenary Part I

ArcGIS Explorer at the BPC Plenary Part I

Excluding reviews of Explorer at conference events, the last four above would be replaced by:

Exploring Crane Lake and the Crane Lake Web Cam

Getting started with the ArcGIS Explorer SDK: your first button

Placing photos in their geographic context

Exploring more of ArcGIS Online

Of the developer/SDK posts, the top three were:

Getting started with the ArcGIS Explorer SDK: your first button

Creating add-ins that execute geoprocessing services

Tip for add-in developers: How to bundle files in an EAZ file

We hope you've found this blog both useful and enjoyable. Please feel free to send us your comments about topics you'd like to see or posts about your own work with ArcGIS Explorer.

Happy New Year!

The ArcGIS Explorer Team

The December, 2009, issue of GeoInformatics publishes a review of ArcGIS Explorer. The article provides a nice overview of features, including support for Layer Packages.

The Arizona Geographic Information Council (AGIC) has recently posted an ArcGIS Explorer workshop presented by Jami Garrison of the Maricopa Association of Governments, who also served as the conference co-chair. Jami also featured her work with ArcGIS Explorer at the 2008 ESRI User Conference.

All workshop materials are available as a downloadable zip file at the AGIC conference proceedings site.

In an earlier post we detailed how you can use add-ins published on the ArcGIS Explorer Labs group on ArcGIS Online. Here's a closer look at one of the add-ins you'll find there, the Yahoo! Traffic add-in.

After you've added it open it and click the magnifying glass to fetch traffic incidents from Yahoo! based on the center of your current view. They'll appear on your map with a variety of symbols that indicate the type of incident.

To clear the incidents, click the red X.

To add one or more incidents to your contents select them and right-click, then choose Move to Map.

Here's some of the current incidents in the greater Philadelphia area. Click an incident to open its popup with more information.

Over the past few years, an increasing number of geo-services and location-based services have become available to the online community.  For example, 3D viewing and street-level imagery from Bing, spatial data layers and services from ArcGIS Online, and georeferencing through GeoNames.  Additionally, new types of location-based and crowd-sourced data services provide traffic data (Yahoo!), information on earthquakes (USGS), photography trends (Flickr), local reviews (Yelp), WiFi-based automatic georeferencing (Skyhook), just to name but a few.

As GIS developers, we can leverage these services (and data) in different ways to build new and exciting applications.

Integrating geo-services into ArcGIS Explorer

ArcGIS Explorer provides developers with a framework to integrate with virtually any type of online service.  Application extensions can be written by developing custom "add-in" extensions with .NET.

In the ArcGIS Explorer Labs, you can find a number of sample add-ins that highlight integrating with different services.  For example, there's one that displays Bing's bird's-eye imagery, one that displays Yahoo! traffic information, and another that allows you to execute a Yellow Pages search from within the application itself.

The Twitter geolocation API

One of the newest services to provide support for geolocation is Twitter. Twitter is a social networking and micro-blogging service that gives users the ability to send or receive short (140 character) status messages (tweets).   This can be accomplished from a wide variety of applications and devices.

With the recent addition of geolocation support, users now have the ability to send geolocation information (Latitude/Longitude) with each status message.  This is known as "geotagging your tweet" or "geotweeting" for short.  Since this functionality is only available through the new Twitter API, only applications that consume the API and that are location aware can support geotweeting. 

It is important to note that applications can only geotag tweets if users have explicitly set their accounts to support geotagging.  Learn more about geotagging tweets and geo-enabling your account here.

The ArcGIS Explorer Twitter add-in

The Twitter add-in for ArcGIS Explorer gives you the ability to geotag your tweets and perform a number geospatial operations against the Twitter API.

Here's a quick break-down of what you can do:

• Map Tweets: Login to visualize all of your tweets on a map (2D and 3D).
  
  
• GeoTweet: Send a geotweet about what's happening at a certain location and provide some information that others might find helpful.
  
  For example:
  
  I noticed a traffic incident on the I10 near the Alabama exit. You may want to avoid this area for the next little while. #Traffic #Redlands
  
  <34.0666, -117.20872> (Geotag)
  
  
• Search: Perform distance or keyword searches and display these on the map.
  
  
• Explore: Interact with the map and show popups to see what people are saying, and where.
  
  
• Create Notes: Convert tweets to Notes and use them with other ArcGIS Explorer tools (find, measure, directions, route etc.).
  
  
• Share: Save the map, upload it to ArcGIS Online and share it with others.
  
  
• Integrate: Further integrate with other ArcGIS Explorer add-ins or ArcGIS services to perform more advanced geospatial and geoprocessing operations.

Here are a few snapshots of what you can do.

Summary

This is just one example of how geo-services can be integrated with GIS applications such as ArcGIS Explorer. With a steady stream new web development frameworks and geolocation services, there are many other interesting and powerful applications that can be developed. 

So if you are interested in exploring what's happening in the Twitter world, or if you are just looking for ideas of how to build future geo-service based applications, feel free to download this extension and try it out.

Steps to download and install the plug-in

Please feel free to leave your feedback.

An ArcGIS Explorer developer course is now available for free via ESRI's online campus. The course focuses on the ArcGIS Explorer SDK and how it is used in Microsoft Visual Studio 2008.

You will learn how ArcGIS Explorer can be extended by creating Add-Ins such as Buttons, Windows, Galleries, and invisible Extensions. You will also learn how to use application configurations to deploy your customizations.

Last week the British Geological Survey (BGS) launched a new web site - OpenGeoscience - a service where users can view maps and access a wide variety of other information. The use of ArcGIS Online basemaps, the same as available in ArcGIS Explorer, was covered in a recent ArcGIS Online blog post. The site features a nice Geology of Britain viewer that uses ArcGIS Online basemaps and JavaScript API.

The site also includes a KML and the shapefile data along with a layer file (.lyr). Here we've taken the KML and added it to Explorer, and used the Bing Streets as our basemap.

We also used the layer file (.lyr) and associated data in ArcGIS Explorer, and also created a layer package from them. Here's the layer package.

The BGS site is a good example of publishing the same content in a variety of different ways, for public users via a Web app, KML, and also the building block data so it can be used and combined with other data for further GIS use.

We've covered embedding YouTube videos in Explorer notes before, but here's a question we got the other day with a new twist - how to automatically play them when opened? It's easy to do, and here's how.

First, we went to YouTube and searched for "ESRI" and came up with the following video. We'll use this as our example, and you can follow along.

We added a point note in Explorer and copied and pasted the provided embed string from YouTube directly into the note. You'll see that you can customize the embed tag by specifying a border, color, size, and more. Here we've chosen a small size video to be framed in purple.

We pasted the string into our note popup in edit mode. While this opened the video ready to play, we still had to click the play button.

To set it to autoplay we edited what was copied and pasted from YouTube and added "&autoplay=1" to the attributes in the embed tag (shown highlighted below):

With this change the video will automatically start playing in the note popup window when opened.