During the first GIS Board meeting of 2020 members reviewed and adopted a recommendation from the GIS Office to improve the spatial accuracy of the county boundary polygon in the state. The Office and the Arkansas Division of Land Surveys have steadily been adding to the public land survey system corner control dataset. Last year the Land Survey Advisory Board recommended and the GIS Board adopted a revision to the fee structure for the Arkansas Corner Restoration Program. The revision increased the reimbursement schedule for Surveyors who provide precision level coordinates when certifying a perpetuated corner record. To learn more about that program visit here: http://surveyor.arkansas.gov/wp-content/uploads/2016/04/Corner-agreement.pdf
This change in the fee structure led to a 57% increase in the amount of certified corners with 0.5 feet or better spatial accuracy. As many of you already know the vast lengths of county boundaries in the state fall on the public land survey system lines. As our PLSS improves so must the county boundary and other data.
Hence the need for a well-reasoned plan and good execution with advanced notice to users.
The Arkansas GIS Board and GIS Office have routinely fostered the use of the County Boundary file, originally produced by the Arkansas Department of Transportation, for nearly two decades. This file and the associated geometry represented a “best in class” for spatial accuracy and quality. Over time, maintenance of the file has incorporated changes dictated by the Arkansas General Assembly through Acts of the Legislature, administratively changing county boundaries in certain locations.
The spatial accuracy and quality of other ancillary data, such as the public land survey system control corners, have dramatically improved over time and will continue to incrementally improve through the work of the Arkansas Division of Land Surveys Corner Restoration Program. To be clear, these incremental improvements in the spatial accuracy do not represent changes of order or magnitude in the location of the geometry. To further understand this need users should explore the PLSS Corner Control Points data – http://gis.arkansas.gov/product/plss-corner-control-points/ and query for records that are greater than or equal to three feet. “Accuracy ≥ 3”
The County Boundary is an administrative record of the State of Arkansas, the legal boundary is only changed by Acts of the Arkansas General Assembly. The incremental improvements in the spatial accuracy of the GIS data representing the boundary are in the order of a few feet to several hundred feet and based on accuracy improvements derived from precision instruments measured at PLSS Corner Control points. For this reason, the GIS Office identified a pressing need to develop a plan to edit the county boundary file to increase its overall spatial accuracy based on the improved control data. The steps outlined in this plan will unfold over the next several years, but the foundation is necessary now.
Due to the extraordinarily high use of the county boundary file by all stakeholders the following major plan steps are outlined:
- Identify all datasets tied to County boundaries, such as Circuit Courts, Fire Districts, School Districts, Justice of Peace Districts, 911 Public Safety Answering Points, numerous administrative districts etc. representing GIS data wholly or exclusively tied to the county boundary location data.
- Identify a listing of exceptions, which primarily represent any data derived directly from 2010 Census Blocks which were developed through redistricting processes such as the U.S. Congressional District, State House & Senate Districts that would remain unchanged.
- Issue a Pre-Release Publication of county boundaries via gis.arkansas.gov in order to allow stakeholders to compare, contrast and identify change areas that may or may not have impact on their respective business processes.
- Conduct edits for spatial alignment to achieve topological coincidence of GIS datasets identified in step 1.
- Prior to the 2021 publication date, rename current asdi.COUNTIES_AHTD to asdi.COUNTIES_AHTD_Archived.
- Conduct internal pre-release testing on all online map applications and programs maintained by the GIS Office.
- Publish a new file titled asdi_COUNTY_BOUNDARY in October of 2020 prior to the U.S. Census release of the 2020 Census Block TIGER files.
- Publish and maintain asdi_COUNTY_BOUNDARY_CHANGE polygon feature and attribute table to track all edits over time.
The GIS Office has completed the first two steps of the plan. In the coming days we will be issuing a pre-lease publication of the data as well as a change polygon and will enable users to visualize where spatial accuracy has been improved. We know understand that many of our constituents have IMPORTANT business processes that rely on these polygons. This pre-lease period will allow a four month review period before the Office moves to Step 5 of the plan.
Users are encouraged to also review the draft metadata for the county boundary file.