Chapter 4: Design Surveys

Section 1: Design Surveys

Overview

Design surveys are an essential part of the design process. These surveys touch on a multitude of specialties including Photogrammetry, Geographic Information Systems, and Engineering Services. Design surveys are defined as topographic data collection for precise engineering decisions.

Roles and Responsibilities

The TxDOT District Survey Coordinator
 shall enforce standards and provide exceptions as necessary.
TxDOT Survey Staff
shall track all project requirements and complete projects.
ROW Division Surveying Section
 shall curate and provide training for all survey standards and processes.
Information Technology Division (ITD) Engineering Services
shall develop software and hardware processes and procedures. They shall also provide training for all processes and procedures that they develop.
Design Division Remote Sensing Services Section
 shall develop processes and procedures for remote sensing data processing. They shall also provide training for all processes and procedures that they develop.
The Design Team
 shall provide all project specifications to District survey staff and provide specific deadlines for receipt of data.

Open Roads Designer

All graphic design survey files shall be provided in
MicroStation Open Roads Designer (ORD)
. These shall follow all standards within the
TxDOT Surveyors’ Toolkit
and seamlessly integrate with TxDOT systems. Only TxDOT ORD formats such as fonts, cell libraries, linestyles, and other graphics styles shall be utilized. It is the responsibility of the surveyor to provide the design team with files in the appropriate format with no further processing required by design to fully utilize the files.

Aerial Data

All data acquired from aerial platforms shall be processed under the supervision of an American Society for Photogrammetry and Remote Sensing (ASPRS)-certified photogrammetrist. Flight plans and photogrammetric procedures shall follow the
Photogrammetry Guide
and
Photogrammetry Feature Collection Standards
provided in the TxDOT Surveyors’ Toolkit.

Precision Standards

Both Schematic and Plans, Specifications, & Estimates (PS&E) surveys shall follow the same precision standards. Level of Accuracy (LOA) identifications come from the
U.S. Institute of Building Documentation LOA Specification Guide V. 3.1
. All Digital Delivery project require higher data density than normal projects, and are specified separately. These standards are below:
  • Horizontal accuracy error allowance:
    • Bridges and other roadway structures: less than 0.1 feet, which is within LOA20.
    • Utilities and improvements: less than 0.2 feet, which is within LOA10.
    • Cross-sections and profiles: less than 1 foot.
    • Bore holes: less than 3 feet.
  • Vertical accuracy error allowance:
    • Multi-phase bridges: less than 0.02 feet, which is within LOA30.
    • Single-phase bridges and other roadway structures: less than 0.04 feet, which is within LOA30.
    • Utilities and improvements: less than 0.1 feet, which is within LOA20.
    • Cross-sections and profiles: less than 0.2 feet, which is within LOA10.
    • Bore holes: less than 0.5 feet.
The guiding principle for point density is to capture all significant detail where it exists, ensuring that the collected data accurately reflects the ground surface and feature geometry for high-fidelity traditional or digital delivery.
  • Spatial density requirement:
    • Manmade features: Maximum distance between measurements is 25 feet; reduce spacing along curves, breaklines, and areas with rapid elevation change to ensure accurate representation where geometry or slope varies significantly.
    • Natural features: Maximum distance between measurements is 50 feet; reduce spacing in irregular terrain or where detail is needed for high-fidelity modeling.
  • Digital Delivery project raw data collection spatial density requirements:
    • TxDOT features: Maximum distance between measurements is 5 feet; reduce spacing along curves, breaklines, and areas with rapid elevation change to ensure accurate representation where geometry or slope varies significantly.
    • Improved features: Maximum distance between measurements is 10 feet; reduce spacing along curves, breaklines, and areas with rapid elevation change to ensure accurate representation where geometry or slope varies significantly.
    • Natural features: Maximum distance between measurements is 50 feet; reduce spacing in irregular terrain or where detail is needed for high-fidelity modeling.
It is the responsibility of the surveyors to understand the capabilities of the measurement devices used for the survey. Recommended practices and procedures are provided in the
TxDOT Surveyors’ Toolkit
. TxDOT District Survey Coordinators shall randomly check data using the recommended practices and procedures to ensure compliance. The surveyor is responsible for reacquiring all data for a survey that does not satisfy the random checks.

Completeness of Survey

Surveyors are responsible for the measurement of all required features in the specified survey area that exists on the date of survey(s). If a survey takes place over multiple months, then all features that exist at the end of the survey period shall be measured and provided to the design team. A list of required features and their measurement methodology exists in the form
ROW-S-DesCheck Design Survey Checklist
and the
Photogrammetry Feature Collections Standards
in the TxDOT Surveyors’ Toolkit.

No Acceptable Failure Rate

There is no acceptable failure rate for any TxDOT survey. Any surveys found not in compliance with the precision and completeness requirements above shall not be considered finished and cannot be invoiced.

Teams to Receive Surveys

Upon receipt of a finished survey, design survey graphics files shall be stored in Projectwise and notification of their location provided to the following teams: District Design Team, ROW Division Commercial Signs Section, and TxDOT District Utility Coordinator. If the contact for any of these teams is unknown, contact ROW Division Surveying Section for support.