|Dispersing Imagery at Mn/DOT with Image Server
By Jesse Pearson, Minnesota Department of Transportation
The Minnesota Department of Transportation (Mn/DOT) uses georeferenced imagery on a daily basis as a backdrop in both GIS and CAD applications and needed a way to disperse large quantities of imagery across the state to all of Mn/DOT’s eight districts. Management and distribution of imagery have been challenging due to the sheer size of the raster datasets.
Image Server Benefits
Mn/DOT chose ESRI’s Image Server product because it eliminated data redundancy and extra storage requirements, provided fast access to large quantities of imagery, and processed imagery on-the-fly and on-demand. One key point is the ability to use Image Server in MicroStation as well as other GIS-based products. Also, the ability to put up services in county coordinates without having to reproject imagery is very important to our business. Testing the system with statewide uncompressed 1-meter air photos, the speed of loading the images reduced the time from six months to load into SDE to six hours with Image Server.
Image Server client tool in ArcMap.
Image services are the final product from Image Server, and these can be deployed to ArcMap, MicroStation and imaging products via an Image Server client tool. ArcIMS and ArcGIS Server applications can also consume image services. The image services can then be bundled up into specific folders on the image server client for easy access by the customer through an Image Server client on ArcMap and MicroStation.
Mn/DOT has organized our image services into four category folders: cities, county, statewide and districts. The user would find different scalable imagery in the different category folders, for example, statewide, project-specific imagery or citywide imagery. Many different types of raster data can be distributed with Image Server, including aerial photography (natural color and infrared), satellite imagery, scanned topographic maps (DRGs), and elevation data.
All of the processing is done on a server and multiple image products can be derived from a single data source. Multiple data formats can also be used to create image services which ease data management and storage problems. Creating a statewide image service with service overviews takes only six hours compared to the previous way of creating statewide raster catalogs which took several days.
Performance and Turnaround
Mn/DOT’s user performance tests showed that image services were quick in ArcMap but MicroStation lagged behind by a couple seconds. In another test, when multiple ArcMap users were connected to the same image service simultaneously the response time was very quick, from .5 to 1 second in most cases.
During the Republican National Convention in early September 2008, we were able to create a WMS-enabled Image Service of georeferenced imagery with a one-day turnaround for the Homeland Security Emergency Management team. This product will be very useful in the future for emergency preparedness and planning.
Image Server is becoming a big part of Mn/DOT’s imagery solution! Now people in the district offices can quickly and readily access updated imagery with two different software products in ArcMap and MicroStation.