Notes

Outline

SECTIONING WILLOW CREEK Capturing Cross-Section Data on Willow Creek Heppner, Oregon October 1995

The Willow Creek Project How much water can be released from Heppner Dam without flooding local farmland or damaging property?  The Corps of Engineers want to know.

Project Requirements Cross Sections must be taken at: Every Bridge Crossing or Every 300 feet In City Limits: whichever occurs first Outside City Limits: at every bridge crossing only

Project Requirements (cont.) Each Bridge Cross Section Must Be: Sketched Photographed Described HI measurements booked Accuracy:  must be within 1/10th foot

Project Location

Terrain

Terrain

Equipment Trimble 4000SSE GPS Total Station Consists of: Base Receiver & Radio Rover Receiver & Radio Backpacks Range Pole TDC-1 Data Logger

Base Station Base 4000 Receiver Base Radio/Amp GPS Antenna Radio Antenna Two Tripods Batteries TDC-1 Data Logger to Start Base

Rover Setup Rover 4000 Receiver Rover Radio GPS & Radio Antenna Batteries TDC-1 Data Logger w/Survey Controller Firmware Backpack & Range Pole

Control Nine Control Points Established Using Static GPS 4  BLM Monuments Basis of Network Max. Distance Between Control Points only 3 Miles

Calibration Requirements Requires Two Independently Obtained Sets of Coordinate Values (i.e. Lat, Lon, Alt & Northing, Easting, Elev) on each Point to be Used in Network

Calibration (cont.) Four Steps to Calibration Datum Transformation Transforms WGS-84 to NAD-83 Plane Projection Moves Project to a Horizontal Plane on a Sphere Plane Adjustment Provides Rotation, Scale Factor, Triangulation Height Adjustment Models Change in Elevation Using an Inclined Geoid Plane

Why Calibrate? Allows Us to Work in Local Coordinates in the Field Can Instantly Verify Accuracy by Comparing Observed with Published Coordinates

Assigned Responsibilities GPS Maintain Lock with SATS Monitor Battery Levels Call back HI Values Capture GPS Data Rod Man Determine Points of Observation Call out HI Values Crew Chief Sketch Bridges & Take Photographs Keep Notes Record All Vertical Values

Day One Started Base Receiver Dam Was Our First Significant Obstruction

Cross Section Data Capture Method

Typical Bridge Crossing in Town

Typical Bridge Crossing in Town

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Day Two

Moved to Base #2 Established Point 25 Feet off Road Surface Moved Base for the First Time at 10:30am Verified New Base Checked Point to North Checked Point to South

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"End of Day Two" End of Day Two Logged 211 Points Approximately 20 Cross Sections

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Day Four Got Out of Heppner Before Noon Cross Sections Were at Bridges Only Some Were Thousands of Feet Apart Data Logging Got Easier (less trees)

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Day Five: Setting Up on Base #4

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Data Logging Finished..... Let’s Discuss Problems.

Problems TREES Only had to see SATS for < 10 seconds Acquired SATS in open, then ran under trees to collect data before losing lock RADIOS Had to move Base 4 times, rather than twice Would had better range with more elevated radio antenna (+15 feet)

Problems (cont.) BATTERIES Rover batteries lasted only 45 minutes (spec says 45-90 minutes) Mixed up charged and un-charged batteries Base batteries were large enough to last all day Charger for Base radio battery barely adequate

Summary GPS Data Capture Went Smoothly Anticipated Use of Conventional Gear Crew Returned with Conventional Gear Two Weeks Later Picked up 9 Cross Sections (90 points) GPS Point Total: 1020 Conventional Point Total: 90 GPS Completed 92% of Project Finished 17 Days of Work in 6 Days

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