GIS Landpoints
 A
control densification project was conducted from 1998 to 2000 to improve the
on-the-ground survey control in
eastern Boulder County. Prior to this project, the positional accuracy of
Boulder County's GIS layers was not adequate to support GPS-based
applications and base mapping requirements. These land points were also used
to create the County digital
ortho photos. The second phase, being
conducted now, is to adjust the County's
parcel
layer.
The resulting primary control points,
secondary land points and
other
(tertiary) GIS
landpoints are useful for surveying, engineering, and GIS, and are provided
free of charge from this website. Please note that these GIS Landpoints cannot
be used for
determining legal boundaries. Boulder County and BASIC accept no liability
for the accuracy of these data.
Purpose
The purpose of the project was to:
- Densify primary/geodetic control to serve as a basis for survey and
cadastral control and to assist in the development of better datums and
geoids by the National Geodetic Survey,
- Create a secondary network of GIS Land Positions to support cadastral
applications,
- Apply cadastral control to County GIS layers to improve their
positional accuracy, and,
- Enhance the survey infrastructure to allow the County, at some future
date, to require developers to submit digital subdivision plats tied to
survey control or GIS Land Positions to significantly reduce the county
workload required to maintain the county assessor parcel GIS layer.
This project was conducted and paid for by BASIC, an informal coordination
group of local, regional, state and federal governmental agencies that
reside in Boulder County.
Overview
Beginning in March 1998, County GIS staff worked with the Colorado
Department of Transportation (CDOT) and the National
Geodetic Survey (NGS) to densify primary geodetic control in eastern
Boulder County. In the Fall, with the addition of other partners, the scope
was expanded to include secondary GIS land positions: Public Land Survey
section corners, quarter corners and centers, and other useful survey,
witness and offset monuments.
Please contact us if you
discover that one of the survey markers or section corners has been
destroyed or if any information contained in this website appears to be in
error.
The second phase of this project is to use the
secondary GIS land positions, and the photo and parcel map identifiable
points (scaled from
the digital ortho photos) to adjust the County GIS parcel layer. This
phase is currently being conducted and should be completed within the next few
months.
Prior to adjustment, the positional error of this GIS layer was about
15-30 feet in eastern Boulder County. After adjustment, this positional error should be reduced to less
than 10 feet. It will also improve the consistency of the positional accuracy. A
viewable sample tile of the Assessor's GIS
parcel layer is available.
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