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DOC Does Marvels With Mega Maps

Robert Yoha and Harold Feinberg of the Department of Conservation's Office of Technology Services can make things very complicated for the technology impaired, talking gigabytes, megabytes, terabytes and other computer stuff with bigger-than-byte-sized names.

But they are in the process of demonstrating that they can also make things as complicated as digital orthophoto quarter-quads – DOQQs, for short -- relatively simple for their peers in the technology business.

Small section of DOQQ showing downtown Sacramento
Small portion of a DOQQ showing downtown Sacramento. The arrow points to DOC headquarters.

Last July, DOC purchased 21 digital linear tapes in a format called UNIX TAR from the U.S. Geological Survey for $28,000 – the cost of reproduction. The tapes contained 10,289 DOQQs, comprising a highly detailed computerized map covering most of the state.

“It wasn’t cheap, but buying them a dozen or so at a time on CD as needed would have cost more than $145,000,” Yoha said. “And when you think about what you’re getting … these maps provide photographic coverage accurate to within a meter anywhere in the state.

“They’re so accurate that people can see positioning errors in paper maps that were perfectly acceptable before. It’s the blessing and the curse of newer technology. As we make better maps, flaws in the older ones become more obvious. It’s not that they were made wrong back then, just that today we are using better technology that can create a more accurate map.”

There were two “holes” in the USGS data set. The DOQQs for those holes were finished last winter and spring. As part of a cooperative effort, the Department of Forestry and Fire Protection provided 98 quarter-quadrangles for northeastern California and the Bureau of Reclamation provided about 700 from the Delta region and central state. DOC now has the best complete set of DOQQs available, covering 99.9 percent of California (a few coastal areas are not mapped, presumably because clouds or fog aborted the aerial photography).

Just what is a DOQQ, how is it going to make DOC’s work easier and why are so many needed?

“Think of them as maps that can show the swimming pool in your back yard,” Yoha said. “They’re accurate enough for engineers and correct enough for lawyers to use in arguments. The DOQQs can be used as a common, more precise reference base map for all the department’s GIS products. Every division in the department will have some use for them.”

Picture of Harold Feinberg and Robert Yoha
Harold Feinberg (L), Robert Yoha

Geologists in the California Geological Survey's Minerals Mapping Program already are using the DOQQs to map gravel quarries when they cannot gain access to the property and map by sight. They have found that the aerial photographic quality of the DOQQs allows them to map a quarry more accurately than by mapping the outline while on the ground.

CGS’ Seismic Hazards Zonation Program is using the DOQQs as a final quality control check on the landslide and liquefaction zones it is creating. Staff can see exactly what may be in the hazard zones – for example, what buildings are on the side of a hill within a landslide zone.

While the Division of Recycling might have GPS latitude and longitude coordinates for a supermarket and its recycling center, the DOQQs provide an actual view of the market, its loading dock and the streets leading to the recycling center.

Once the data were obtained, the challenge was to simplify the material – to put it in a format that could be shared and easily used. The large file size presents a problem to most users, so Feinberg and Yoha used compression software called MrSID to make them smaller. Now someone working on a laptop can access the data. Feinberg and Yoha are creating a version of the data in GeoTIF, a universally used GIS product.

If moving data from a complicated format into a more user-friendly, industry standard format sounds simple, it isn’t. Feinberg was obliged to write more than 3,000 lines of code to transfer the data into MrSID.

“Everyone wants to do different things with the information, so the first challenge was to create a compressed version that everyone could handle,” Feinberg said. “My role was to facilitate that procedure. It was a very challenging project, from both a technology perspective and the magnitude of the size of the data being handled. I had a choice of doing each quarter-quad individually or creating a way to do a big batch all at once, so I wrote a program to do the batch all at once. That probably cut the project time in half, but it still took more than a week.”

Feinberg took on the challenge when he moved from CGS to OTS in mid-January, wrapping up the MrSID conversion in May.

“It was more or less a 24-7 job, managing the disk space and server space, keeping an eye on things,” he said.

He is now working on two projects that should wrap up in the next couple of months: converting the relatively few map segments that are in color to black and white to produce a uniform data set and also finishing the GeoTIF files.

At this time, DOC is perhaps the only state department capable of handling all the DOQQs. The data set – the original and the reformatted material – totals 1.6 terrabytes (more than a million megabytes). OTS had to build a special server – unique in state government -- to handle the data. Other departments may follow suit.

“Our GIS capabilities are much farther along than most other departments,” Yoha said. “We have more than a hundred GIS users in 16 program areas. The size of our infrastructure allows DOC to do this large a project.”

But DOC is not going to hog the data. Copies are being made for the Department of Fish and Game, the Department of Forestry and Fire Protection, the California Conservation Corps and the U.S. Bureau of Reclamation. The California Energy Commission, Department of Food and Agriculture and other agencies all have shown interest in using the DOQQs.

“Everyone wants this data,” Yoha said. “The USGS is quite happy that we’re sharing the information with other state agencies. We’re supplying it to them as a matter of goodwill and to build better connections in the GIS community.”

User-friendly versions of the data also will be given to the NASA Ames Research Center, which is building a Web site for researchers, and to the Resources Agency’s California Environmental Resources Evaluation System (CERES), a Web page post office that directs users to data holdings throughout the state.

Director Darryl Young has dubbed Yoha and Feinberg’s GIS operation “Industrial Light and Maps,” a takeoff on George Lucas’ movie-making Industrial Light and Magic.

“Here in the GIS shop, our motto is, `Our business is to help you do your business,’ “ Yoha said. “We’re here to help people work better.”