Intermodal Transportation Division
Engineering Technical Group
Engineering Survey Section

June 12, 2000

To: Allen Instruments (Trimble)
7114 E. Earll Drive
Scottsdale, AZ 85251
Attn: Todd Ferris

Corvallis Microtechnology, Inc. (CMT)
413 SW Jefferson Ave
Corvallis, OR 97333
Attn: Eric Gakstatter

Surveyors Service Co. (Leica)
4317 N. 16th Street
Phoenix, AZ 85016
Attn: Gary Gibbs

Holman's (Sokkia)
1320 S. Priest Dr. Ste. 102
Tempe, AZ 85281
Attn: Anthony Trujillo

From: Britt Bowen
Manager, Engineering Survey Section

Subject: Demonstration of GPS Equipment
Thank you for demonstrating your equipment for ADOT / Engineering Survey Section. GPS is the future for surveying and especially in Arizona with our wide open skies.

There are four companies with geodetic grade equipment, which have state contracts with the State of Arizona. Engineering Survey's is required to buy our equipment off of one of the contracts, which is why we looked at the systems on the four contracts. Our goal is to buy four RTK GPS bundles (base and rover).

The equipment will be used: 1) to survey photogrammetric control points, 2) to do RTK locations type surveys, and 3) to do stakeout of roadway alignment centerline, 4) to establish control and publishing control coordinates. Engineering Surveys would also like to eliminate differential level run whenever possible, especially on our surveys of photogrammetric control points.

The demonstration asked each vendor to set up their base at a known point and then survey several other points in an RTK mode. The coordinate of the known point was provided. ESS had already done a GPS static survey of the points of interest and run differential levels. Our numbers were used as baseline numbers for comparison purposes.

The criteria used to evaluate the equipment included: accuracy, reliability, durability, ease of use, weight, company support, and cost.

The following chart shows what equipment was used in the demonstration:

Table 1. Demonstration Equipment
Company Equipment Cost for RTK -GPS Bundle (Including
Base, Rover, Radios, Software, Cables,
Poles, etc)
Trimble 4700 and 4800 $45,000
Leica SR530 $35,100
CMT Z33 $28,000
Sokkia Radian $37,300

Some Obervations:

Trimble's system was the most integrated system. CMT, Leica and Sokkia systems were similar in number of components and cabling.

Trimble, Leica, CMT has smooth demonstrations. They were able to set up their base, establish radio link, and survey their points without any glitches. Sokkia had radio link problems. Sokkia was the only vendor using the new Pacific Crest radios with one touch channel changing capability.

The reliability and durability of the systems was hard to assess from a one-time demonstration. All the vendors provide similar warranty packages.

All the system are much light now than in the past. The weight of all four systems is similar. The weight of the rover backpacks and poles are now manageable for all four systems.

The "ease of use" was a subjective evaluation and it is difficult to make definitive statements based on a one-time observation. Given that, the following observation is made: Trimble has done an excellent job of integrating the total system including the user to do survey work. CMT, Leica, and Sokkia are not far behind Trimble. From a practical point of view as it relates to training new crewmembers to operate the equipment, all the four systems would have a similar learning curve and take similar amount of time.

Trimble, Sokkia, and Leica have support personnel in state. CMT would support the product out of Oregon.

As shown in Table 1, equipment cost range from $28,000 to $45,000 with CMT at the low end and Trimble at the high end.

Table 2 shows a comparison of the coordinate values obtained in each demonstration. All four vendors performed well. All four vendors integrated the Geoid model into their process. In the X and Y coordinates all the vendors did very well. In the Z coordinates, Trimble and CMT did a little better than the Leica and Sokkia system.

There are four conclusions from this demonstration.

1. There is technical parity in the market today. All four systems are able to get accurate results. All four systems integrate the Geoid model into the data processing.

2. As far as reliability, durability, ease of use, weight, company support are concerned, the four systems are close in their packages, with no package having a distinct advantage. Trimble had the best integration of the total package and fewest components. CMT, Leica, and Sokkia all had good systems with similar number of components.

3. Radio reliability is the weak link in the RTK process. Each of the four vendors use Pacific Crest radios. Trimble also markets their own radio in addition to the Pacific Crest radios. As such there is no market advantage to any vendor on this critical link in the process at this time.

4. RTK GPS is becoming a commodity. As with any product that is a commodity, product differentiation will be based on price and service.

Given that there is technical parity and no other distinct advantages that differentiated the systems, the distinguishing characteristic is price. With that as the basis, the following three questions were asked, "What system is the lowest priced?", "Will that system meet our needs?", and "Given that the other vendors were higher priced, did their system have a capability that the lowest price system didn't have and was that capability worth the price differential?"

The CMT Z33 system was the lowest price system at $28,000. It meets our needs as described above. It has the technical accuracy that is needed. It gives the data collection and data processing capabilities that we needed. I could not in good conscience justify the price differential between CMT and the other three vendors (Sokkia, Leica, and Trimble). As such, the CMT Z33 system was selected.

Once again thank you for taking the time to demonstrate your equipment. Each system is a quality product and each vendor did a thorough and professional demonstration.

If you have any question please feel free to call me at (***) ***-****.


Britt Bowen
Manager, Engineering Survey Section

View Coordinate Comparisons