.NET Rocks!
Road Trip Tracking

Fig 0 - Tracking a RoadTrip


Overview

Microsoft is on the move this fall. Win8 is the big news, but Visual Studio 2012, .Net 4.5, a revamped Azure, WP8, Office 2013, and even a first foray into consumer hardware, Surface Tablets (not tables), all see daylight this fall.

The Net Rocks duo, Carl Franklin and Richard Campbell, are also on the move. Carl and Richard head out this week for a whirl wind tour through 36 states in 72 days or roughly 1728 hours. The DNR Road Trip Tracking application, http://www.web-maps.com/RoadTrip2012/, keeps tabs on the .Net Rocks RV with Tweet encouragement for the road weary travelers. All are welcome to follow the DNR RV online and add Tweet comments at #dnrRoadTrip. The app gives event information and up to the minute updates of time to next show with tweets along the route. It even gives turn by turn directions for those inclined to catch the .Net Rocks RV and follow along in the real world – .NET Rocks stalking.

Technical Overview

Project Outline

Fig 1 – .Net Rocks Road Trip Tracking app project outline

Backend:

SQL Server Azure is the key resource for the DNR tracking app. GPS feeds are pushed at 1 minute intervals from a commercial Airlink GPS unit to a Windows service listening for UDP packets. This Feed Service turns incoming UDP packets into Feed records stored in SQL Azure with a geography point location and datetime stamp.

On the same system, a Twitter Query service is checking for Tweets on a 30 second interval using the Twitter REST API. Tweets are also turned into Feed records in SQL Azure. However, the geography point locations for Tweets are pulled from the latest GPS record so they are associated in time with the location of the GPS unit in the DNR RV.

Frontend:

Fig2 – Windows 8 IE10 browser showing stop and routes

On the front end, an Azure WebRole provides the UI and WCF service for communicating with the SQL Azure Feed data. In order to handle the widest spectrum of devices, this UI leverages jQuery Mobile sitting on top of HTML5. jQuery Mobile Supported Platforms

Inside the app divs (jQuery Mobile <div data-role=”page”..> ) are maps leveraging Bing Maps Ajax v7 API. The UI client also accesses Bing Geocode and Bing Route services through a proxy.

Fig 3 – IE9 on a laptop with GPS dots and Tweet icons along the way

Some more details:

Routes

Since there are several thousand points for each ‘event to event’ route, these are stored in SQL Azure as geography LineStrings. Using SQL Server spatial functions, the routes can be simplified on query for improved performance in both network latency and map rendering. SQL Azure’s geography Reduce(factor) function is a thinning algorithm that reduces the number of vertices of geography features while maintaining shape integrity. In this app the reduce factor is tied to zoomlevels of the map, thinning the number of points returned to the UI.

The map viewport is used as a bounding box STIntersect so only the visible routes are returned. Obviously Carl and Richard may find reasons to take a different route so the GPS breadcrumbs may wander from the Bing generated routes.

Tweets

Fig 4 – WebMatrix iPad simulator

The Twitter REST API queries are simple search by hashtag queries:
http://search.twitter.com/search.json?q=%23dnrroadtrip

To avoid returning lots of duplicate Tweets the search is limited by the last since_id in the Feed table. There are some caveats to REST Twitter searches:
“Search is focused on relevance and not completeness. This means that some
Tweets and users may be missing from search results

Fig 5 - webmatrix WP7 emulator

Fig 6 - iPhone simulator

GPS points

GPS points are generated every 60 seconds while the RV GPS unit is powered on. When the vehicle is off, and power is scarce, the unit still sends a packet once every 4 hours. Carl and Richard will be driving a lot of hours and there will be lots of points generated over the next 72 days and roughly 1728 hours. Assuming a 25% driving time over the duration, there could be as many as 1728/4 *60 = 25,920 GPS locations. Even Bing Maps Ajax v7 will choke trying to render this many locations.

In order to keep things more reasonable, there is another thinning algorithm used in the GPS query service. This is again tied to zoomlevel . At lower zoom levels points are thinned using a type of decimation – every 20th, 10th, 5th point, etc is kept depending on the zoomlevel. In addition only points required by the viewport bounding box are returned. Once the map is zoomed to higher resolution (zoom > 11) all of the points will be returned.

GPS map locations include a rollover infobox with time and detected speed at the location. We can all check up on Carl’s driving (moving: 86.99mph) and keep track of coffee stops (moving: 0.0 mph).

Bing Routes

Routing services are provided for user position to the latest GPS location and Stop venues selected on the map or from the Stop list. In addition to the route map a turn by turn directions list is provided as a page option. The GeoLocation API is used for identifying a user’s location for these routing requests. Geolocation API is an opt in API, so users need to allow location sharing to have their location automatically available. If allowed, getCurrentPosition returns a latitude, longitude which is run through the Bing reverse geocoding service to get an address used as the ‘from’ field for routing requests.

Fig 7 - Stop Detail with Maps.Themes.BingTheme()

Fig 8 - Bing Route Denver to Seattle Stop

Fig 9 - Bing Turn by Turn directions

jQuery Mobile

jQuery Mobile is a javascript library for abstracting away some of the complexity of supporting a large number of devices. WP7, Win8 tablets, iPads, iPhones, and Android devices are multiplying while traditional laptop and desktop systems have a number of browser choices and versions. jQuery Mobile is not perfect but it is a great help in a project that had to be ready in about ten days from start to finish.

One interesting feature of jQuery Mobile is the page transition effect. These are based on CSS3 and are not supported by all browsers. It adds a little pizazz to see slide, flip, and pop effects for page transitions.

JQuery Mobile apps do not have access to device native sensors such as accelerometer, compass, gyrometer, etc , so jQuery Mobile webapps will not have the full range of capabilities found in custom apps for Win8, WP7, iOS, and Android. However, just one web UI for all is an enticing benefit, while deployment is ordinary webapp rather than a series of more complex app store submissions. This approach allows easy updates over the course of the tour.

Fig 10 – Microsoft Way on an Android AVD emulator

Heatmaps
Collecting some locations always leads to the possibility of heatmaps. These are value gradients which are helpful for analyzing geospatial data.

Fig 11 – Tweet heatmap along tour route from Seattle to Wyoming

Maybe it’s pretty obvious where Tweets are concentrated, but how about locations of app users who share their location. Australia is hot, India is not. Guess who listens to .NetRocks! Or, at least who’s less cautious about sharing location with GeoLocation API. User heatmaps bring to mind some intriguing possibilities for monitoring use, markets, and promotion effectiveness.

Fig 12 - GeoLocation users world wide

Summary

On the Road Again