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Operational Review #7
PO.DAAC
- Describe in a sentence or two your overall operational experience related to WMS. (e.g., scientific visualization; geospatial visualization, etc). What kinds of WMS servers and/or clients do you have experience with? (e.g., commercial products, open source, or independent implementations, please provide as much detail as possible).
- We use WMS 1.1.1 as the protocol for POET, a 2-D visualization tool at PO.DAAC. I developed the WMS server on my own, as well as a customized client. I am familiar with the Digital Earth, World Wind, and similar viewers.
- What types of applications do you use WMS servers/clients for? Are they suitable for your applications? (e.g., Do they work well with the data types and data manipulations in your application?)
- WMS is very appropriate for visualizing our Level 3 data. It is our primary protocol for accessing PO.DAAC on-line data. It is less suitable for Level 2 data (WFS) or for obtaining raw data values (WCS). We find that we must offer two versions of GeoTIFF: 32-bit (to provide floating point values) and 8-bit (for browsers to understand).
- Why do you choose to use WMS over other protocols for your applications?
- The use of WMS gives outside clients access to our data. It is straightforward to develop clients and servers. OPeNDAP requires client plug-ins and users must carry out the translation between rows/columns and lat/lons.
- Are the WMS systems easy to use? (e.g., Is it hard to learn how to use WMS systems?)
- WMS is very easy to use. It is very easy to write a client.
- Does the performance of the WMS systems you have experienced meet your requirements? (e.g., Does it take a long time to access/view data in WMS systems?)
- Performance is generally adequate.
- What operational challenges do the WMS systems present? (e.g., Does it require advanced processing power, large amounts of memory, complex configuration, etc.? Are the systems easy to deploy and maintain?)
- Generally, WMS systems are very fast and easy to maintain. There has been a tendency to look upon WMS systems as experimental, so not all systems are fully maintained. The greatest disappointment is the lack of a centralized, up-to-date catalog of WMS servers.
- How well do the WMS systems scale to large numbers of simultaneous users, or to large datasets?
- Scalability is entirely dependent upon the server implementation, so there is a wide variability in performance. The largest servers use wavelet-type representations or tiling of large images to reduce the data retrieval time. We sometimes experience slow performance when many requests occur simultaneously. We are implementing a service where a WMS request is handled off-line, that is, the user receives an e-mail when the maps are ready to be retrieved.
- Can you provide information on user statistics of your WMS systems? How have the user statistics changed over time?
- Our WMS served 15,000 distinct hosts in 2005. We have usage records for the past four years.
