Public Comment (2) - Laserfiche WebLink

CLINGMAN Bill W Aug 12 at 1:08 PM To Gunnar Schlieder All of our regionally-maintained GIS layers, including site address points, zoning, plan designations, taxlots, city limits, and many others, are projected into the same State Plane coordinate system, and all of them are intended to align with the other layers to a degree which meets the various business needs of the end users, such as planning, elections, assessment and taxation, etc. Historically, a taxlot layer has served as the "base" against which other layers have been spatially aligned, but all of these GIS layers have individual histories extending back to before they were first digitized. Taxlots in Lane County were originally drawn by hand, ink on linen or ink on mylar, one map sheet at a time, many of which were later converted into CAD drawings, but still just one sheet at a time. The original digitized GIS taxlots were created and maintained by LCOG but were used only for planning purposes, while the official taxlots were still maintained, outside the GIS, by Lane County. That first unofficial GIS taxlot layer formed the original "base" against which other GIS layers were spatially aligned as they were converted from their hand-drawn forerunners, even though that taxlot layer was considered spatially accurate enough only for planning purposes. Over time, the regional GIS layers have evolved in terms of spatial accuracy, maintenance responsibility, storage architecture, and coordinate system. For example, in 2004, the regional GIS layers were all shifted from the North American Datum of 1927 (NAD 27) to NAD 83. Because they were all subject to the same datum shift, their relative spatial alignment with each other was not affected, and the taxlot base was still considered spatially accurate enough only for planning purposes, and was not an official representation of the taxlots. In 2006, that original GIS taxlot layer, maintained (for planning purposes only) by LCOG, was replaced by a new, more spatially accurate, GIS taxlot layer maintained by Lane County as the official source of taxlot maps (replacing the old CAD and mylar drawings). Due to the increase in spatial accuracy, and the fact that the old taxlot layer was more inaccurate in some areas than in others, all of the other regional GIS layers needed to be "spatially adjusted" to align with the new taxlot layer. This work was done in part by LCOG and in part by other regional GIS partner agencies. The intent was to preserve the relative spatial relationships between these layers, but again, they are intended to align with each other to a degree which meets the business needs of the end users, which for the most part, do not require precise registration. Over the entire history of the regional GIS, some layers have been more precisely aligned (or registered) to the taxlots than others. For example, annexations (from which City Limits are derived) are defined by legal (metes and bounds) descriptions, and care is taken to register them to the taxlot layer with some degree of precision. Most other layers, such as plan designations, including those shown on the Metro Plan Diagram, are not typically defined by metes and bounds descriptions, and have not been precisely registered to the taxlots. Prior to the advent of the regional GIS, the Metro Plan Diagram was also originally drawn by hand, and early versions of the Diagram have sometimes been referred to as "blob diagrams" due to their highly generalized depictions of the various plan designations. When the Metro Plan designations were first digitized, they were similarly generalized. Even now, after several iterations of adoption and amendment, it is worth noting that the only version of the Metro Plan Diagram that is considered official is the one produced at the 11 X 17 size and scale, on which the designations are depicted over a single-line representation of major streets and roads.