horizontal_control

Points with horizontal corrdinates

For survey and other position controlling needs

20020204:  New horizontal_control.shp is created to update SAT_PT.shp.  Older SAT_PT.shp was created in March 12, 1997 and did not reflect HPGN conversion.  See 1999 Horizontal Control Network documentation for more detail.

The original GPS survey conducted by Hunsaker & Associates  in 1990 used the control point "Monterey" as the primary  horizontal control. That point had a coordinate and scaling  factor established for the NAD 83. Additional stations  called "KSLY" and "KVEC", also having coordinates  established by Caltrans, were also used to provide  horizontal control. 15 additional primary and 132 secondary  control points were established for horizontal control by  Hunsaker & Associates. These points were each assigned a  horizontal coordinate, a convergence and a scale factor.  The City staff in-filled between these points to establish  the centerline street system on the same horizontal basis.  Traverses were run between control points tying in points  with the subdivisions. Distances measured were adjusted by  scale factors. While every point in the map does not have a  first or second order coordinate, all points relate by  survey to a first or second level control point established  by Hunsaker & Associates. The  City's 1990 horizontal control points were converted to the  metric NAD 83 (1992) datum based on a survey and report  generated for the City by Penfield & Smith in August 1996.  The following steps were used to convert the points:  1. The City's 1990 control points were first converted to  metric units by applying a conversion factor of  0.3048006096. This was done by scaling an Autocad drawing  file containing the City's control network. 2.  The control network was then translated (using City's pt.  no. 201-"Monterey"as a reference) to the published NAD  83(1992) coordinate of said point. (This was possible  because the scale factor for both the 1983 and 1992 systems  is the same.) 3.  The City's control network was then rotated so that the  azimuth between the City's newly translated "Monterey" and  "KVEC" was equal to the NAD83(92) based azimuth between  Monterey and KVEC established by Penfield & Smith. The  NAD83(92) coordinates for Monterey and KVEC are shown on the attached excerpt from Penfield & Smith.