Primary control points will be referenced to the National Spatial Reference System (NSRS) through or . Primary control points shall not be more than approximately two (2) miles apart and shall be set in intervisible pairs to provide redundancy. Primary control points shall meet the Level 2 accuracy standards as listed in the . Surveyors are responsible for knowing whether their equipment and methods can meet these standards.

Surveyors shall endeavor to ensure that control covers the entirety of the project area in a stable planar configuration as shown in the . A control layout, provided in the TxDOT Surveyors’ Toolkit, shall be provided to the TxDOT Survey Coordinator prior to control point monument construction.

Construction of primary control monuments shall be done with the intent that they survive for future projects. Whenever possible, they shall be in TxDOT right of way and situated away from likely construction. Construction methods and materials shall match the diagrams and processes outlined in the listed in the TxDOT Surveyors’ Toolkit for primary control monuments.

All primary control points shall be documented on a form (in the TxDOT Surveyors’ Toolkit) and shall be signed and sealed by a Texas Registered Professional Land Surveyor or Professional Engineer. These control data sheets shall be stored and indexed by the TxDOT District Survey Coordinator for future projects and open records requests. Primary control points shall also be included on Plans, Specifications, and Estimates documents and any ROW Mapsheets developed for the project. These control points shall also go into any computer-aided drafting (CAD) graphics files generated for the project.