Vertical Control

Vertical Control in Eastern Arapahoe County

Between the years 2000 and 2005 Arapahoe County established a primary Vertical Control Network in the eastern portion of the county.The network consists of five separate phases with one phase completed per year.As shown on the index map, the primary Vertical Control Network extends from Watkins Road to the Town of Deer Trail.

Vertical Control Purpose

The purpose of the network is to establish a series of benchmarks that can be used for mapping, surveying, engineering design, drainage studies and construction purposes. There was difficulty establishing phasing lines in the first two projects. In the end it was decided to call the first project Phase I and the second project Phase II. It should be noted that Phase I has been revised. The purpose of the revision is noted on the cover sheet.

Classifying Surveys

For all five projects all elevations are referenced to the North American Vertical Datum of 1988 (NAVD88) and were established by differential leveling. All field and office procedures followed FGCC 1st order Class II Specifications. However, the controlling benchmarks for the surveys used to establish the network are classified as Second Order, Class 0. Therefore the surveys used to establish the network are classified as Second Order, Class 0 as defined by NGS.

Please read the notes on the cover sheet of each project for more information on the methodology used to establish the elevations. Full survey reports for each individual project are on file in the offices of the Mapping Section. Due to road construction some of the benchmarks in Phase I were reset in 2006.

Available Maps and Documents

    Benchmark Recovery Project

    In 2010 the county conducted a benchmark recovery project to verify the existence and condition of the benchmarks in the Primary Vertical Control Network. It should be noted that the county only verified the existence and condition of the benchmarks and did not check or verify the elevation on individual benchmarks and did not check or verify the difference in elevations between the benchmarks.

    2010 Vertical Control Benchmark Recovery information by Phase:

      Vertical Control in the Urban Area

      In 2010 the County began establishing a Vertical Control Network in the urban area.Since the City of Aurora has established its own Vertical Control Network, the county's network will extend from the western boundary of the City of Aurora to the western boundary of the county.The first phase was completed in 2011.

      Purpose of the First Phase

      The primary purpose of the first phase was to extend existing NGvertical control along East Hampden Avenue in the City and County of Denver into Arapahoe County.As shown on the index map this phase also established a series of benchmarks in the area between South Monaco Street and South Havana Street north of East Arapahoe Road.

      Establishing Elevations

      The elevations established by this project are referenced to the North American Vertical Datum of 1988 (NAVD88) and were established by differential leveling. All field and office procedures followed FGCC 1st order Class II Specifications.However, based on field verification, the existing NGbenchmarks used to control the Phase I survey can only be classified as Second Order, Class I.Therefore the Phase I survey is classified as a Second Order, Class I survey as defined by NGS.

      Please read the notes on the cover sheet for more information on the methodology used to establish the elevations. A full survey report for the project is on file in the offices of the Mapping Section. The county has recently completed the second phase of the network by establishing two benchmark loops off of the primary loop established in Phase I.

      Available Maps and Documents