A Closer Look
The USDA Forest Service is one of the first federal agencies to implement the new ArcGIS Image Server. Mike Morrison, training and technology awareness program leader for the Forest Service's Remote Sensing Applications Center (RSAC), frequently receives questions about the software and how his agency is using it. Here are the top five questions he has received and his responses.
Q: If you're on a wide area network, instead of a local area network (LAN), how fast are you really seeing the data?
A: The speed of the system on the LAN is one to three seconds per screen refresh. When you're off the LAN, it slows down by one to two seconds with an average of two to five seconds per refresh. Our users are very happy with that. Part of this is due to changeable compression, which many people ask about. The datasets from i-cubed are JPEG compressed GeoTIFFs. Other datasets are not. On transmission, by default, the data is JPEG compressed for fast speed and little quality loss.
Q: What is the quality like? How does it look?
A: The quality is not that of raw data, but it's compressed so people expect that. The majority of our users are very happy with the clear imagery ArcGIS Image Server provides at 1:2,000 scale. Users can also vary the transmission compression to balance speed for quality.
Q: How easy is it to set up ArcGIS Image Server? And, what do I have to do as a client to get access to the imagery?
A: Both of these are quite easy to do. The client-side setup is very simple; it's just like installing an extension. Access to the imagery once the client is in place just requires one click on an icon and then you're into it. There are also directories that make it visually easy for users to navigate.
Setting ArcGIS Image Server up is also quite easy. It's a well-developed program, and Esri has set it up so the install is simple. It's easy to get it operational and to build the image services and publish them out. You don't need someone who knows Oracle to set up this software. What is helpful is to have some understanding of imagery and different file types, but you don't necessarily need an IT person or database manager to help you through the process.
Q: What hardware do I need to operate ArcGIS Image Server?
A: When we did the initial testing on this, we only had one server, a Windows 2003 server with a dual processing unit and four gigs of RAM tied to a six-terabyte NAS [network attached storage] box. We stood up three of the main services: the 1-meter dataset, the 1:24,000 DRG [digital raster graphics] dataset, and the eTOPO dataset. With 150 people receiving these services, it was running quite smoothly. We didn't have any mainline issues. Now, of course, we have more servers tied to it and a lot more storage capacity.
Q: How stable is it after it's been in operation for a while?
A: We've found the product to be very stable. We had our formal launch in
October 2006, and the service has only gone out on us two times for a total of about
15 minutes lost service. It's been running for many months, and that's the only issue we've had with itthat's pretty good.