North Dakota Pilot GPS Project

Presenter: Judy L. Froseth

Lory Harsche

The Problem:

• Crash location information has been maintenance intensive and difficult to code. Engineering staff has expressed concerns with these problems.

GPS Pilot Objectives:

• Collection– Ensure the data format is accepted and

usable• Test data entry screens for data acceptability• Test data retrieval to ensure proper format

– Ensure data collection is simplified• Easy use of GPS units• Quality instructions provided to the officers

GPS Pilot Objectives:

• Collection (continued)– Collect 500-750 crash reports with GPS data

• Ensure significant quality of crash reports in pilot • Review the handwritten data format for correctness • Ensure GPS unit provides data consistent with

data standard • Check GPS unit configuration options for

consistency • Ensure data is collected when the GPS unit has a

strong signal lock

GPS Pilot Objectives:

• Collection (continued)– Collect law enforcement officers’ feedback

• Discuss GPS use, function, performance, questions, issues

GPS Pilot Objectives:

• Use– Import/export crash data into a GIS system for

analysis, testing and review • Provide the system with GPS and crash report

data • Review the export/import process for efficiency,

make changes• Use electronic and paper node maps to compare

GPS and node point location data

– Provide feedback to officers

GPS Pilot Objectives:

• Use (continued)– Have experts examine the data results to

ensure data meets accuracy requirements, is consistently collected and is usable

• Assemble the panel of experts • Determine what is required to analyze the data • Review the analysis, make recommendations to

correct problems • Discuss statewide implementation

GPS Pilot:

• Revise the MVCR form to provide space for GSP coordinates

• Required close communication between:– Traffic Safety– Planning and Programming– Information Technology

• Form was revised and printed in December 2001

GSP Pilot:

• Two law enforcement agencies:

– Bismarck Police Department in January 2002 – Cass County Sheriff’s Office in February 2002

GSP Pilot:

• GPS Units: – Magellan Meridian

GPS at $235 each

GSP Pilot:

• GPS Units:– Garmin eTrex Legend

at $265 each

GSP Pilot:

• How did officers view this “extra” duty?– As part of the crash data collection process to

provide more accurate data – Collection of GPS data became part of their

daily routine

• Which GPS units were preferred?– All officers preferred the Megellan, based on

ease of reading the numbers

GSP Pilot:

• GPS Unit: – Magellan Meridian

GPS at $235 each

GSP Pilot:

• How has the durability been?– There have been no known issues

• What have been the pitfalls/problems? – GPS units provide a continuously reading

number – Officer must select the 5th decimal digit from

a fluctuating readout – The 5th decimal represents roughly 1-5 feet of

change

GSP Pilot:

• Have officers reported difficulty receiving signals/getting a reading?– One crash report indicated a reading was not

possible due to heavy rains – Officers are not returning to the scene when

the report is completed elsewhere

GSP Pilot:

• What is the battery life?– Battery life depends on frequency of use – Bismarck PD uses about 2 sets per month – Cass County used original batteries for over

4 months

Technical Field Accuracy Comparison:

• Manufacturer’s specifications on accuracy: – Magellan Meridian GPS

• WAAS enabled up to 3 meter accuracy

– Garmin eTrex Legend • 3 Meters – 95%, 15 Meters – 5%

Technical Field Accuracy Comparison:

• Field Accuracy Test Comparison– Based on 5 random locations near the

Bismarck Capitol – Tests were performed in a side by side

comparison mid-day June 5th – Trimbal Pro/XRS GPS unit was used as the

comparison

Technical Field Accuracy Comparison:

• Radial difference in feet from the point identified by the Trimbal:

Maximum Minimum Average

Magellan 52 feet 16 feet 24.8 feet

Garmin 36 feet 1 foot 16.2 feet

Data Collection/Preliminary Results:

• As of July 26, 2002, 300 total crashes have included GPS data

• About 30% of crashes reported by the 2 agencies have GPS coordinates

• Initial analysis identified data collection/entry errors, requires a check

• A non-labor intensive checkpoint process is being worked out