Clay County government officials are taking a look at geographic information systems for precision parcel mapping.
Plexis Group, a division of Beam, Longest and Neff consulting engineers and land surveyors, presented three required steps to four different mapping methods earlier this week.
First, aerial photography, corrected for the curvature of the land, is done as a foundation. Then planmetrics is completed to digitize in various features from streams to utilities. Finally, parcels are put in with deed dimensions.
Coordinate Geometry, or COGO, is the most accurate option and requires surveyed deeds on top of aerial photography; Precision Digitizing utilizes up-to-date platbooks on top of aerial photography; Board Digitizing is only as accurate as existing paper documents and relies on a computer technician's judgment for placement onto photography; Scanning and Vectorizing takes existing paper and fits it as close as possible onto the photography.
Rob Williams, technology coordinator, explained when the different options are used. Plexis uses only the first two options for parcel mapping and methods vary in cost and accuracy.
COGO is used when original platbooks are out-to-date, when aerial photography is not available, when accuracy is critical, when time is not a major factor because research can consume quite a lot of time and when money is not a major factor. Precision Digitizing is used when existing platbooks are current, legible and include dimensions, when aerial photography is available, when time is a factor and when money is a factor.
Williams said Plexis recommends COGO for Clay County, mainly because existing platbooks do not meet requirements for Precision Digitizing.
"If we can find a proper way to fund it, without putting an additional burden on taxpayers, you would have my vote to go ahead with COGO. I think others would benefit from this technology as well, such as the city and utility companies. They may be interested in helping the county with funding to have access to it. Funding could also come from tax reassessment money," Joe Dierdorf, county auditor, said.
COGO can be used as a building block for future zoning of utilities, precincts and addressing. More information is available such as parcel numbers, deeded acreage, dimensions, right-of-ways and more. Plexis has done work for counties with as much as 400,000 parcels to as little as 20,000. Clay County has 22,500 parcels.
"Once research is completed, it will take about another 12 months to finish COGO. If we do the research, it will take about 12 months. If you do the research in-house, it would save money. The cost would be about $10 per parcel without research. If Plexis does the research, the cost will double to $1/2 million," Jack Larrison, sales support, said.
Steve Luther, Beam, Longest and Neff vice president, said BLN contracted Synder aerial photography firm three years ago and that it was possible to utilize those photos for COGO, which would also save some money. Based on source documents already in place, Plexis did a quarter of a section of land in Clay County to show those in attendance an example of potential parcel mapping capabilities.
"We're still using the platbook system from 50 years ago. On behalf of county employees, I can tell you that if we don't get COGO, we don't want to spend money on something else that isn't an improvement. We've already spent money on aerial photography with WTH a few years ago for parcel mapping that makes a pretty picture, but we can't use it for the taxation purpose it was intended," Mary Jo Alumbaugh, first deputy auditor, said.
COGO is a one-time expense that can be utilitzed by future generations as long as it is updated every four to six years Williams said.