Machine Control Data Preparation

Overview

Machine controls are devices attached to heavy equipment (ie: graders, scrapers and dozers) to assist the equipment operator in adjusting the blade to achieve maximum productivity. The control system utilizes an on-board computer to store a digital terrain model of the area to graded. The system references the position of the equipment in relation to the site base station by GPS or laser total station.

Data preparation is required to translate grading plans so they can be referenced by the machine controls. The digital terrain model or DTM is combined with background data. This allows the equipment operator to see both plan and cross section views of the site. Trimble offers both the SiteVision GPS and Blade Pro 3D machine control systems. Terramodel has the ability to convert DTM data directly from the desktop to the machine control format.

With the advent of machine control technology, the number of stakes required for most grading projects is reduced significantly. Once the primary control is set, the operator can reference the on-board system to obtain grade information such as cut, fill and slope grade.

Grading contractors will rely more upon the machine controls to provide grade information. Grade checkers will also utilize the digital data. Survey field crew time on site will be greatly reduced. This will reduce revenue as large staking contracts will become a thing of the past. However, grading contractors will still need someone to develop the DTM and background data for the machine control systems.

Data prep requires a CAD workstation with Terramodel or similar software. Terramodel modules should include all Survey and COGO functions along with Roadway and Site Design.

Data Prep Assembly Procedures

Project preparation time depends on how the data is developed prior to preparation. If all design work is performed electronically using 3D coordinates the task is much simpler. However, simply having contours in Autocad is not enough. All slopes must have highly accurate design edges. Gutt sections of roads must be calculated and converted to templates for the Roadway module to perform cross sections and create breaklines.
Research

The first step is to gather pertinent plan sets and electronic data. Meet with the client to review the plans and determine DTM limits, street section requirements and detail level. A thorough examination of the plans and data should be made prior to estimating time and cost of deliverables.

DTM Assembly

Use an electronic mapping base if available. Otherwise assemble one from the Final Map. The building pads in a typical subdivision are controlled by the lot lines. The rough grade plans will provide a typical section with information on bench from property line to top / toe of slope. Using this information along with the pad grades, begin building the pads by off setting from the lot lines. The pads must be created with points and breaklines in order to be incorporated into the DTM surface. It will be necessary to calc the horizontal offset from top to toe based upon the difference in grade and slope ratio required.

The roads are created next. The callout grades on the rough grading plans are usually not sufficient for this task. It is necessary to create the roads based upon the street improvement plans. In Terramodel this is accomplished by creating the centerline alignment, vertical profiles and assigning shape templates for transition areas. The roads are then created as a DTM surface automatically with points and breaklines. The pad frontages can then be adjusted accordingly to the street sections.

Add details as required such as basins, cross drains, facility access roads and park sites. This portion of the assembly requires great care as often plans for different facilities may have conflicts. If a basin or park site is shown as proposed contours they can be converted or digitized to 3D points and breaklines to be incorporated into the DTM. Perform quality control checks and clean up any erroneous areas. For Sitevision export the DTM as a “.ttm” file.

Background Assembly

The background data is what the operator sees on the machine control display in plan view. Once the DTM is complete generate polyline contours. If the project site has excessive elevation changes it may be necessary to include only the index contours in the background to reduce clutter. Copy the breaklines from the DTM and convert to 2D lines to save filespace. Add text labels to lots that include lot number and pad elevation. Label street names. For Sitevision export the Background as a “.dxf” file.

Deliverables

Deliver a CD ROM to the client with the DTM (.ttm file), Background (.dxf file) and a Digital Data Agreement.

MONUMENT DESCRIPTIONS FOR FIELD NOTES

When you find a monument ask the following and write it down:

WHAT did you find? (Iron Pipe, Brass Cap, Hub, Size, Plug, Tag Stamping, etc…)

WHERE is it? (Section Corner, Intersection, Property Corner, etc…)

HOW is it’s condition? (Up, Down, Leaning, etc…)

WHY is it there? (Reference Map, Corner Record, etc…)

Example:

Found 1” Iron pipe w/ Plastic Plug, “PLS 7717”
Centerline Intersection Walnut St. & Hesperia Road
Down 0.3’ in A.C. Pav’t
Per RS 123/12-13

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