Before I get into the details of how Microsoft Location Server works, you’ll need to familiarize yourself with the following terminology :

With this introduction to the key terminology used in Microsoft Location Server, let’s see how it works to obtain real-time location from the cellular phone networks.

Microsoft Location Server does not require GPS-like hardware to get real-time locations; instead, it locates a provisioned user’s mobile device by communicating with a mobile operator. In a typical scenario, a user requests her position using a client that communicates with Microsoft Location Server; this client can be a mobile phone (such as a SmartPhone) or a portable computer (such as a laptop).

When Microsoft Location Server receives the request from the client, it identifies the mobile operator for the user and sends a location request to the mobile operator. The mobile operator responds by sending back the real-time location of the user, expressed as latitude and longitude coordinates. Microsoft Location Server then returns that location to the user’s client, where it can be used for rendering a map or finding nearby points of interests, depending on the application. All communications that are specific to a mobile operator are hidden from end users and developers. Thus, Microsoft Location Server works as an aggregator for mobile operators by abstracting implementation details specific to the mobile operator to obtain a real-time location. Figure 9-1 summarizes this process.

Figure 9-1. How Microsoft Location Server works

One important thing to keep in mind is that the accuracy of the locations returned by the Microsoft Location Server depends on the mobile operators and methods used to locate the devices on their networks. For example, some cell phone carriers use cell tower triangulation technique to determine the location of a phone; in this method the phone’s location is determined by the cell towers around it. As you can imagine, this method does not always yield an accurate location. Some carriers use an assisted GPS technique, which results in a very accurate location of the phone. Table 9-1 provides an overview of technologies used by different network carriers and the approximate location accuracy of each technique used.

Now that you know how Microsoft Location Server works in general, let’s look at the internals to understand its architecture.

Microsoft Location Server consists of three core components :

In this section, I will go through each one in detail.

Microsoft Location Server Providers

Microsoft Location Server providers are software plug-ins required for communication with mobile operators. Usually, there is a location provider and a notification provider for each mobile operator. Because the implementation of location and notification providers is unique to each mobile operator, Microsoft Location Server does not currently expose APIs for developing location or notification providers.

The Microsoft Location Server includes a demonstration location provider for testing purposes. This demo provider simulates real-time location scenarios against a configurable file with phone numbers and associated latitude and longitude pairs.

Working with the Demo Location Provider

There are a few scenarios where you may need to use Demo Location Provider (a plug-in that actually talks to mobile phone carriers to get the location of a mobile phone) for programming with MapPoint Location Server:

• Your mobile phone carrier is not (yet) supported by MapPoint Location Server.

• You want to develop a demo application before asking the actual phone carriers for a location.

• You want to test/troubleshoot your MapPoint Location Server application without using the mobile operator’s network.

In these cases, you can use the Demo Location Provider that ships with Microsoft Location Server. The Demo Location Provider works off of a text file to return a simulated location for a provisioned user. You can manually edit this text file and hardcode locations against the provisioned phone numbers for testing purposes.

The good news is that no extra code (that is specific to the demo provider) needs to be written to work with the Demo Location Provider. To locate a phone number using the Demo Location Provider, follow these steps:

1. Add a user (provision the phone number) either using the MMC or Server API.

2. Add Demo Location Provider as the location provider for that user.

3. Edit the TestLocations.txt file located in the Program FilesMicrosoft MapPoint Location ServerMLSWebServiceBin folder to add a simulated location for the user’s mobile phone in the following format:

       Mobile Phone Number, Status Code, Latitude, Longitude, Delay

So, an example simulated location for a mobile phone—for example, (425) 555-1212— would be:

    14255551212,Success,47.6446802586242,-122.130220099595,1

Now you can locate this phone number using either the locator clients that ship with Microsoft Location Server or the APIs.

Tip

For more information about the demo provider, see the Microsoft Location Server Administrator’s Guide, Version 1.0, which is included with Microsoft Location Server.

Figure 9-2 shows how all the core components work together to obtain the real-time location of a mobile device.

Figure 9-2. Location Server architecture

Now that you know the core components of the Location Server and how they work together, let’s look at how to install the Location Server within your enterprise.

In a production environment, Microsoft Location Server components should be distributed among multiple computers for security reasons; however, when you are developing and testing Microsoft Location Server applications, you may want to install all the components on a single computer. In this section, we’ll see how to set up your Microsoft Location Server environment and install Microsoft Location Server on a single computer for development and testing.

To use Microsoft Location Server, you also need a valid MapPoint Web Service account. For more information about MapPoint Web Service or to sign up for a MapPoint Web Service evaluation account, visit the MapPoint Web Service web site at http://www.microsoft.com/mappoint/products/webservice/default.mspx.

Microsoft Location Server Web Service allows you to develop real-time location-based services, such as finding your exact location or locating your contacts’ exact locations. This web service also provides API functionality to manage contacts and privacy settings for any given provisioned user, making programming with Microsoft Location Server Web Service no different from programming with any web service.

Once you have successfully installed Microsoft Location Server, you can access the Location Server Web Service APIs using the following URL:

The Location Server Web Service is hosted by your enterprise on your full domain name that is only accessible via any valid provisioned enterprise user credentials. To program with this web service, you can either use WSDL.EXE or Visual Studio .NET (2003 or later) to generate .NET proxy classes that can be added as references to your project.

Using the Microsoft Location Server server-side APIs, you can develop a variety of applications that can be run on any Microsoft Location Server; it is important to keep in mind that the applications developed using the Server APIs are purely Microsoft Location Server administrative applications and are not related to any real-time location scenarios. Administrative applications for Microsoft Location Server can be categorized into four major categories:

Keep in mind that all of the above-mentioned functionality is already available via the Microsoft Management Console (or MMC) for the Microsoft Location Server ; however, there may be instances where you need to write scriptable applications as part of the Location Server administration, which is where the Server APIs will come in handy.

To build such applications, how do you access Location Server APIs ? When you install the Microsoft Location Server successfully, you will see the following Location Server Management APIs installed as part of the server installation:

To develop Location Server applications, copy the aforementioned assemblies to your development machine and either add them to your local Global Assembly Cache or copy them to your local application Bin folder.

Additionally, to develop Location Server Applications, you also need sufficient privileges to access the Location Server Database. You also should have an SSL root certificate on your development computer to establish a more secure connection to the computer running SQL Server. Note that in the Microsoft Location Server environment, the database server is configured with Microsoft Windows authentication mode. Your enterprise domain alias should have proper access rights to connect to the Microsoft Location Server Database.

Finally, to successfully run a Location Server management application, the account running the application must be a member of the MLSADMINISTRATORS security group.

Before we cover the detailed programming aspects of the Microsoft Location Server, Table 9-2 shows a list of mobile network providers that are enabled to work with Microsoft Location Server in various countries.

There are currently many other mobile network providers working with Microsoft to enable locating via Microsoft Location Server.

In this chapter, we have looked at the architectural details of the Microsoft Location Server and how it works to obtain real-time location of a mobile device from the mobile carrier networks. The real-time location web service is hosted within an enterprise (not by Microsoft). Location Server also provides Server Management APIs for administrative application development, such as user management, contact management, and privacy management.

Next, let’s look at programming with Location Service APIs and Location Server Management APIs in detail.