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Author: dkimball Created: 2/5/2010 7:04 PM
Thought on the application of mobile technology in the public safety arena.

 The simple answer is, we haven't been able to find an implementation for GeoLocate for any cellular data modems. There have been some hints that someone somewhere has made an attempt, but we can't find any real offerings. And not all of teh browsers expose an API if one would want to implement the interface.

Our need was to access GPS data form a local WAN attached MP890 modem and update the user's position on a map as they moved. We wanted to avoid sending the user's GPS data to the server to minimize network traffic. And this had to work on all browsers!

The solution was to use jsonp. We developed a JavaScript application that accesses the data and updates the map. Problem solved.

Though there is a footnote. jsonp can create significant memory usage. We ended up spending almost as much time dealing with (and solving) the memory leak as we did building the modem interfaces.

The Geoserver map server supports the generation of map layers using data extracted from SQL databases. This seemed an ideal mechanism to use to capture and share status information among several independent agencies and the utility companies that service their communities.

 We tested this capability using mock weather related data (trees down, roads closed, etc.). The Geoserver was able to build a feature layer of Events which we overlaid on a street map. As the map view was zoomed in and out the feature layer queried the SQL database displaying the features with the latest data entered by other users simultaneously using the same application.

 

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In our travels we've often heard that deploying map using the standard ESRI tools can be cumbersome and expensive.

To be honest, we don't know if this is true. But we do know that recent releases of ArcGIS servers will present data in formats that are compatible with Openlayers javascript libraries widely used by the open source community. We've added map layers from numerous ESRI servers to our Openlayers applications. The WMS and the REST interfaces are available by default from ESRI and in our testing both required little or no effort to access.

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We've been wondering just how difficult it is to add external map layers to an existing map. In our case, these would be maps used by public safety agencies, so we were interested in first Weather, then topology. At the end of the day these were easy additions to make.

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 We've been experimenting with ways to better synchronize the street names on a map with the results of a map search. When we had separate files for the map images and the street names the results tended to have small inconsistencies. Using one file fo rboth solved the problem.

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With the rapid growth in data traffic over the cell network, there are bound to be network related issues. On occassion, the tower itself may be failing. The challenge is pinpointing the problem.

 

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Organizations that deploy hundreds and thousands of devices dependent upon WAN communications have access to a rather meager set of network diagnostic tools. Often contact with the carrier begins at a rather basic level, where the intital question can be "Is it plugged in?" Only after you've completed a litany of questions pertaining to the environment and your identity do you begin to discuss the problem.

There are ways to be better prepared to work with the carriers to solve WAN related problems.

 

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Over the past twenty plus years we've been involved with innovative methods of connecting remote and mobile workers with useful electronic information.

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