Tag Archives: wifi

All,

This is the first of several postings on the topic of map caches and mobile applications. This initial post will discuss how applications developed using the Mobile SDK work cache map data and then present some key strategies for deploying mobile map caches to devices. Subsequent posts will discuss best practices for requesting map data from the server, how you can leverage Microsoft API’s to optimize when you make server requests, and much more.

Critical to applications developed for use in the field is the ability to function both connected and disconnected from a network. When you are out in the field you are often either moving in and out of coverage (wifi, cellular) as you work or for various reasons cannot be connected at all. The architecture of ArcGIS Mobile was designed with the full range of connectivity scenarios in mind… 

In order for your mobile application to view and edit maps when not connected to a server, the map cache must be stored locally on the device. The map cache is both a folder full of map data and a component in the SDK. Using the MapCache component, you can request map data from the server and post new and updated features to the server. For a full description of the architecture of the map and map cache components we recommend you start by reading the overview topic.

Disk space may be cheap but access to the data you store on disk is very expensive. For that reason, it is extremely important to consider an appropriate data deployment strategy so that your field workers are always armed with the data they need to be successful in the field.

Some key factors that you should consider when planning your deployment strategy:

• When and how frequently do your field workers need to synchronize with the server?
• How large an extent will they work through when disconnected?
• What map layers are critical to the success of their field work?
• What devices will be used in the field and how will field workers get connected?

In addition to the factors mentioned above, determining the right information and transactional model for the field is critical – do not simply publish maps designed for use in the office. Determine what information in your enterprise database is required to accomplish field projects and design your map with the target device and work conditions in mind.

You can use the Extractor sample that ships with the Mobile SDK to build a map cache that can then be deployed to mobile devices before they leave the office. Once you have created a map cache, you can then copy that map cache to either the main memory on a mobile device or to a storage card. If you have a handful of mobile devices that you need to deploy data to, you can cradle those devices and use Microsoft ActiveSync to copy the cache to the device. If you have a large number of devices to manage, there are several third party tools in the market today that can help you deploy map caches. Microsoft’s Systems Management Server and SOTI’s MobiControl are two mobile deployment applications that we have used. 

By deploying map caches to devices when they are in the office, then your application need only use a cellular or wifi connection in the field to post changes made on the device or to retreive a small amount of data for a subset of the layers in the map. This will not only improve the performance of your mobile applications but reduce the high cost of data transfer.

In the next post we will provide examples of how to request data from the server and how to leverage events on the MapCache such as RequestCompleted to manage requests made between the device and the server.

Let us know how connected you are? What is the dominant connectivity scenario faced by field workers in your organization?