METHODOLOGY & TESTING PROCEDURE

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2 METHODOLOGY & TESTING PROCEDURE Bartlett & West is committed to using the MidStates VRS system going forward into We realize that having a state wide VRS will mean a savings of time on our projects which will translate into a direct savings in cost for our clients here in North Dakota. In order to gain a level of confidence with the system and resulting data, Bartlett & West conducted a series of field tests around the central and western parts of the state. For this testing, we were primarily looking to answer three specific questions: First, how well does the data repeat to itself? Second, how well does the data repeat to existing published control data? Third, how easy and effective is the system to set up and use? Based on our meeting with the NDDOT and Frontier Precision, it was determined that existing control points from various NDDOT projects spread around the central and western parts of the state should be used as the control set. Primary survey control for the NDDOT is based on an NGS OPUS Solution. The vast majority of our internal projects at Bartlett & West are also tied to control which is based on OPUS Solutions. 20 NDDOT highway projects were selected in 18 counties, six survey crew chiefs participated in the testing. Data was gathered between October 28, 2015 and November 16, 2015 on 69 monuments, including NGS and NDDOT OPUS primary control points. Between one and seven control monuments were occupied for each of the highway projects selected. Three NGS horizontal monuments were also selected (Discovery II monuments), as well as the four NGS benchmarks in Bismarck and Mandan. All GPS poles were checked for plumb and heights were verified prior to any field work. Job files were created with Trimble Access and utilized the US State Plane 1983 North Dakota Zones (North or South) Geoid12A, Int. ft. settings. All data in the field was collected in grid coordinates. Each crew was assigned several counties to verify either NGS or NDDOT OPUS published data. Once monuments were recovered and determined to be undisturbed, a Trimble R10 rover and bi-pod were placed and leveled on an indicated center point. All measurements were taken using a minimum 180 epochs (approximately three minute measurement). Each monument was occupied at two separate occasions, with a minimum of four hours between measurements. A majority of the monuments were measured on separate days rd St S Fargo, ND MidStatesVRS.com

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5 Data Summary The mean horizontal residual of all test points surveyed was The mean vertical residual of all test points surveyed was Northing Mean = Standard Deviation = sigma = to sigma = to Comparison of B&W surveyed points Easting Mean = Standard Deviation = sigma = to sigma = to Elevation Mean = Standard Deviation = sigma = to sigma = to Comparison of avg. B&W surveyed points to published data Northing Mean = Standard Deviation = sigma = to sigma = to Easting Mean = Standard Deviation = sigma = to sigma = to Conclusion We were very satisfied with the results when comparing the data as surveyed by Bartlett & West in the test study, which shows a high confidence level of repeatability of the VRS system. In comparing our averaged data to the published control data, we anticipated approximately double the values of the B&W data, which it generally was. Some of the causes include: the NDDOT control monuments have been in the ground a number of years; a variety of consulting firms performed the OPUS solutions; OPUS solutions are based on a least squares adjustment using CORS stations; etc. Setting up the Trimble equipment for the VRS system is just a matter of creating a Survey Style, GNSS contact, and Wi-Fi connection. This took less than ten minutes of setup time, with instruction provided by Frontier Precision. Job startup in the field is no different than standard GPS RTK procedures, with the exception of verifying a proper Wi-Fi connection and selecting your broadcast format before performing work. We now have sufficient data to use in the future when we setup our company standards at Bartlett & West. Going forward in 2016 our internal project control will be utilizing the Midstates VRS system in place of OPUS solutions. With no base GPS to setup, the VRS system speeds up field operations, causing a significant increase in efficiencies in longer/larger projects, which in turn will save our clients time and money. Elevation Mean = Standard Deviation = sigma = to sigma = to rd St S Fargo, ND MidStatesVRS.com