The parcels are updated and maintained by the cadastral technicans daily. A series of automated computer jobs are run each night to assemble all the parcels into a single digital map. Once this is run the property infromation is then attached to the digital parcel map.
It takes a lot of computing power to support these processes. We use several servers to perform the different tasks. The main server is a Sun Microsystems UNIX based machine, this runs the main mapping software the cadastral technicians use. Its a solid, reliable computing platform, so reliable its only been rebooted about 4 times during the past 2 years and that's because we needed to move it. We also use a LINUX based system as a general file server, which is also very stable. The web mapping system runs on a Dell server using a windows operating system.
In order to store all the data, including the aerial photography (ortho-photos) requires almost a terabyte (TB) of hard drive space. As we add new ortho-photography this will continue to increase.
Yakima County has used a GIS (geographic information system) since 1992. "GIS" is the term used to describe computer based maping and analysis. The software is Arc/Info version 9 and it runs on the UNIX platform. The combination of Arc/Info and UNIX has proven itself to be a mature, reliable, secure system. We can customize the software to adapt to new requirements and go to work each morning knowing it will be up and available for use all day.
We also use a piece of software called Arcview (version 3.3) for the majority of county employees. A permit technician or planner can use this software to help their customers determine the location of floodplains, zoning types, critical areas or the general layout of their property with the use of the ortho-photo and other digital map layers.
There are newer versions of the GIS software available but we have made the decision not to use them. They are not as mature and stable as our current system. The newer software is also quite a bit more expensive and would require re-writing thousands of lines of computer code. At this stage it is not feasible nor are there any advantages to using the newer software.
Yakima County processes its own aerial photography for use in our mapping system. This saves us considerable money and provides higher quality control over the final product. In order to create ortho-photos we use software from Leica Geosystems called the Leica Photogrammetry Suite (LPS). This takes raw aerial photography and turns it into ortho-photos.