Section Corner Identification in Madison County

Section Corner Identification in Madison County Presented by: Erin Dyer

Elusive Section Corners • 20 years ago, plats and legal descriptions based on estimated section corners resulted in bad data • Projects were hampered by the inability to acquire accurate coordinates

Base Map Standardization • In 1985, the City’s base maps were standardized and output to large scale maps using corners from Quadrangles • Subdivision plats entered using PLSS had frequent errors because the corners in the field did not match those scaled off on the base maps

Road to Accuracy • In 1987, GPS coordinates were used to georeference base maps and for ground control of mapping projects • Positional accuracy for base maps leaped forward • GPS technology was new and costly; locating and documenting section corners was impractical at the time

Subdivision Regulation • In 1994, subdivision regulations were implemented requiring state plane coordinates for all points defining a subdivision boundary • These coordinates were based on the City’s GPS monuments • The input of subdivisions based on section corners problem was solved

Legals and LOMARs • Legal descriptions entered weekly all begin at a section corner thus requiring significant manipulation • In 2005, a LOMAR dispute ensued between a developer and the City because of an 80 ft difference between the referenced section corner and the mapped section corner • The solution involved additional work and untimely delays

Enough is Enough • Gone are the days when GPS was expensive and sparsely available • Local surveyors are already collecting section corner data • Tim Barnes approached the Tennessee Valley Professional Land Surveyors Society and proposed the SCID Program

SCID Rules • Corner Information must be submitted only by surveyors licensed in the State of Alabama. No blind Submittals will be accepted. • GPS occupation of the corner is preferred although in some cases traditional surveys combined with GPS occupation will be accepted • GPS occupations and traditional surveys should be performed in compliance with The Standards of Practice for Surveying in the State of Alabama • All submittals are voluntary and subject to publication. • Data may be submitted online or in hard copy to The City of Huntsville GIS Division. • Data submitted will not be a direct entry into the database. It will be reviewed and published by the GIS staff. • Submittals for the same corner will be published on a first come, first published basis. • Only section corners, quarter section corners and meaningful ancillary points will be accepted. • Disputes over corner coordinates shall be submitted to the City of Huntsville GIS division for review. • To avoid duplication of database records, all coordinates will be published as the Northwest corner.

SCID Pitch • Local surveyors would occupy purported section corners or quarter section corners with GPS units during their normal business routines • They would voluntarily submit the coordinates to the City’s GIS Division • The GIS Division would publish the coordinates on an Internet site • The GIS Division would also agree to move the base map corners to the GPS’d coordinates

Fields: Key Township Range Section Corner Meridian State Plane Zone Easting Northing NAVD 1929 Latitude Longitude NAD 1988 Determination Method Location Date Description License Number Submitted By SCID Database

SCID Submission • Created website www.hsvcity.com /gis/SCID/SCID_index.htm where the rules are posted along with a data submission form that can be submitted via FAX, USPS or email

Data Entry • Data is keyed in to a ArcSDE database table • An XY Event theme is created from the XY data in the database table so that each new record automatically displays as a point on the map

QA / QC • We decided to publish corners as the Northwest corner to prevent duplicate entries • The Key field is summarized for unique record counts to prevent duplicates • Utilizing the XY event theme curtails typos in the XY fields

ArcIMS & SCID • ESRI’s ArcGIS was used to create the .mxd • ESRI’s ArcIMS software was used to create the interactive map service / website • The XY Event and other layers displayed are pulled directly from the ArcSDE server • The XY Event allows the tabular data to display immediately in ArcIMS as point features

Interactive SCID http://gismaps.hsvcity.com/website/scid/viewer.htm

SCID Search • Search spatially by Zoom and Pan tools

SCID Search • Search records by Find or Query tools

SCID Statistics • Located Corners Statistics • NW Section Corners: 162 • NW Corner of the NE ¼ : 59 • NW Corner of the SW ¼ : 57 • NW Corner of the SE ¼ : 33 • Ancillary Points: 9 Total Points Collected: 320

SCID Results • Legal descriptions for easements, minor subdivision plats, rights of way, zoning lines, annexations and other land parcels are an easier fit to base map data • The pincushion effect (where many pins are driven into the ground around a purported section corner because one surveyor refuses to hold the existing monument because he believes his 1/100 ft difference is more correct) is lessened • Technical problems are being solved and the cooperation between the public and private sectors benefits all

Section Corner Identification in Madison County