King County Road Services - Survey control

The fundamentals

Our skeleton is the human body’s reliable framework. Just as the human body needs a reliable frame, surveying and mapping projects need an accurate horizontal and vertical reference framework. Today’s county surveyors use both a global reference framework supported by Global Positioning Systems (GPS) satellites as well as the historical framework derived from surveying records archived from the 1850’s.

Several fundamental principles govern survey control. First, the world is not flat. Second, water flows down hill and third, surveyors have ignored that science has proven that the earth is not the center of the universe. Surveyors have always assumed the earth to be the center of the universe. Everything circles around us. Surveyors reference and define all horizontal and vertical control based upon this assumption.

Horizontal and vertical survey control

Simply means how high and where something is on the earth. These are measurements.

Take a minute to think about what people need to know for which an accurate elevation and location is required. What would happen if modern civilization was unable to determine the elevation and location of man made and natural features? The transportation industry would greatly be impacted along with the public’s water, sanitation, utility, communication, and other infrastructure systems. We would be incapable of delineating flood, earthquake, volcanic, tsunami and other hazardous zones.

Global Positioning Systems (GPS)

Is a current enabling technology, which is providing cost efficient solutions to determining positions on the earth down to the size of a nickel.

Greater urban growth, higher land values, more land use restrictions, and potential destruction of monuments justifies the continuing need to complete survey control measurements on essential monuments in King County. By using GPS, survey control costs are reduced, however urbanization has shown why there is an on-going need for more survey control positions on boundary and right of way monuments.

King County Survey Control Projects

King County has benefited from its investments in survey control projects. The first surveys in King County were performed during the 1800’s as part of U.S. Rectangular Land System when Washington was a part of Oregon Territory. The initial point of origin for Washington State, the Willamette Stone in Oregon, was established and adopted in 1851. Over ninety percent of Washington was surveyed into one-mile square sections prior to the 1900’s for the disposal of land to private landowners.

The early Government Land Office (GLO) surveys in some aspects were horizontal control surveys that established section and quarter corners at half-mile intervals. The significance of said corners is that nearly all divisions of land ownership (cadastre) were based off of these corners. Although the accuracy of the early GLO Surveys for measurement between corners at half-mile interval should not exceeded 16.5 feet, quite a few did. This degree of accuracy hardly would suffice as the value of land, improvements and settlement in King County increased.

Logically, the need for better survey control and positional measurements on the GLO corners became key elements in any of the King County Survey Control Projects’ scope. Co-operative partnerships were needed to help to fund the execution of the following noted King County Survey Control Projects.

King County Aerial Survey (KCAS)

In 1936, King County undertook a major property land use survey that was financed by the Federal Works Progress Administration (WPA) and concluded in the 1940. The program employed an average of 600 people. Original records can be found at the King County Archives and Record Management in addition to those at the King Street Map and Records Center.

Upon the advice of the Coast and Geodetic Survey Office, the directors of the Aerial Survey decided to run a traverse, controlled by triangulation, to tie and monument all know or recoverable section, exterior quarter and meander corners and establish permanent monuments at convenient angle points on the traverse utilizing second-order specifications. The final positions of the monuments were to be computed in Washington State Plane Coordinates (N.A.D. 1927 and N.G.V.D 1929 datums).

Much of the work required setting up steel and other towers over the triangulation stations as shown by this 1937 picture of a tower over station Pinnacle in King County, where the primary control positions were derived measuring angles and solving triangles.

Information from the Road Services Division's Web site is available to people with disabilities in alternate formats upon request by calling 206-263-6482 or 711 for the TTY relay service.

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