Module 6 - FAQs

1. How and where do I save the data?
   
   
2. How do I publish my data using a particular brand of software?
   
   
3. How much time will it take to implement a web map server?
   
   
4. How do I make these XML documents?
   
   
5. What happens to the rest of my application if one of the web map servers it accesses is not available?
   
   
6. The OGC specifications can be very long and hard to read. Are there any other documents that are as informative but shorter?

1. How and where do I save the data?

You cannot save the map data since you are viewing it dynamically. The map data is stored and maintained at the provider’s site. A web map server provides a view of a map, not the actual map itself.

2. How do I publish my data using a particular brand of software?

Because the CGDI promotes multi-vendor interoperability, you should refer to OGC’s developers’ cookbooks for the general process, and then follow the specific instructions provided to you by the vendor for the software of your choice.

3. How much time will it take to implement a web map server?

The level of effort required to implement a WMS depends on many factors: the nature and volume of your data, your budget, available resources, organizational restraints, etc. Once implemented, however, you can use, combine and re-use your web map services to make your applications more “geospatially aware” without having to build the GIS functionality yourself.

4. How do I make these XML documents?

The specifications for SLD and WMC documents are very thorough, and can quite be complex for the newly initiated. XML authoring tools are available to simplify the creation of XML documents. Also, vendors who are promoting these specifications often have user-friendly interfaces that write these documents for you. Another way to write them is to examine existing documents to see how they were created and what their effect is. Any way you do it, the return is well worth the effort as you see the map come alive.

5. What happens to the rest of my application if one of the web map servers it accesses is not available?

It depends on the way a client handles errors at the network and/or specification level. You could simply be missing that layer of information, or the server which provides the WMS could be unreachable or down for maintenance. Different WMS clients handle these issues in different ways, depending on what level of error occurs (invalid WMS request, host unreachable, etc.). Some WMS clients do not show any map information if one server is down, whereas others do show all successful requests. Consult your WMS documentation on how erroneous behaviour is handled.

6. The OGC specifications can be very long and hard to read. Are there any other documents that are as informative but shorter?

You can start by re-reading this module. Also, be sure to consult the OGC cookbooks at http://www.opengeospatial.org/resources/?page=cookbooks.