Survey & Construction Newsletter, Late November 2008

November 20, 2008  - By 0 Comments

Oh, What to Buy in These Challenging Times

I receive many requests for advice and/or recommendations from folks who are looking to buy GPS/GNSS equipment for survey and construction. Of course, if they haven’t told me, the first question I ask is, for what type of project are they are planning to use the equipment?

Some are typical projects like topographical surveys and construction staking, while others are not-so-typical. But no matter what type of project it is, the common denominator is the need for high precision data. It may be real-time or post-processed, networked or base-to-rover, single frequency or dual frequency, single constellation or multi-constellation, machine control or man-pack – it could be any of the above, as well as other configurations. But … no matter what … it has to deliver high precision results.

Although it may not seem like it, there is a myriad of GPS/GNSS equipment that will provide high precision, or centimeter (cm)-level positioning. To people who are knee-deep in the industry like you and I, it’s a daunting enough task to wade through all the different GPS/GNSS products to find the one that fits the best. To a first-time purchaser, it can be absolutely confusing and mind-numbing to sift through the brochures, Web sites and flyers.

To further complicate the purchasing process, prices can vary widely. I’ll give you an example. Within the past few months, I’ve been forwarded copies of quotes provided to prospective purchasers of GPS/GNSS equipment and asked to comment on them. You might be amazed at the variation in price.

Two quotes in particular caught my attention. One was for a Spectra Precision Epoch 25 RTK system. Spectra Precision is owned by Trimble Navigation. The Spectra Precision Epoch product line is distributed by Tripod Data Systems (TDS), which is also owned by Trimble. The other quote was for a Trimble-branded R8 GNSS system. The R8 GNSS is Trimble’s top-of-the-line GPS survey system with all the bells and whistles you can get these days on a GPS survey system. I’ve used the R8 GNSS and it’s a sweet ride.

Essentially, the Epoch 25 and R8 GNSS can accomplish the same tasks. Both are dual-frequency RTK systems. The Epoch 25 is dual frequency, GPS-only (no GLONASS), and doesn’t support GPS modernization (L2C and L5). The R8 GNSS supports GPS modernization (L2C and L5) and it supports GLONASS. The R8 GNSS is a much sexier package. It is a single, lightweight unit with the radio/GSM modem fully integrated inside a single unit. The Epoch 25 is essentially two pieces instead of one; the receiver itself and the antenna with a cabled connection between the two. There are other subtle differences, but like I said, for the most part they can both accomplish the same tasks and deliver the same precision, although the GLONASS option on the R8 GNSS has some definite benefits in terms of working in areas where the sky is obscured.

What do you think the price difference is between the two systems?

The R8 GNSS system quote was U.S. $56,900. The Epoch 25 system quote was U.S. $19,000. That’s a big difference.


This isn’t meant to pick on Trimble, because the entire industry is the same. In fact, there is a saying I’ve heard for years: “If you don’t like today’s price, check again next Tuesday.” That’s especially true in these economic times when there are fewer potential purchasers of GPS/GNSS equipment so manufacturers and dealers must add more incentive to attract buyers.

When considering purchasing GPS/GNSS equipment, price isn’t the only thing. Local support is an important consideration for most buyers. Local support means technical support as well as sales support (spare parts, etc.). For some buyers who aren’t as technically savvy, it’s obviously even more important. Another variable is that some dealers are more technically competent than others. It doesn’t do you any good if you know more about the system than the local tech representative of the company that sold it to you.

Which GPS/GNSS Equipment Is Right for Me?

Answering this one question will help point you in the right direction:

Do I need the results in real-time, or can I wait until I process the data back in the office (or with a laptop in the field)?

The answer to this question will make a big difference in the type of systems you should consider. Also, the answer might not be so easy. If you are making a first-time purchase for your surveying firm, you may not know what type of projects your business will be working on a year from now. If you really think you’ll be doing a lot of construction staking and sizeable topo surveys, then it’s pretty clear that RTK is the way to go. If you aren’t sure, then a lower cost pair of single frequency receivers may be the way to go. The return on investment (ROI) for those is pretty quick because they are reasonably inexpensive compared to a full-blown RTK system.

Systems for post-processing (a pair of single-frequency receivers) can be purchased for well under U.S. $10,000 and deliver centimeter-level horizontal/vertical measurements. Establishing site control is a good example of how those can be used. However, staking of any kind requires real-time kinematic (RTK) positioning. Also, while post-processing can be used for topographic surveys, RTK is a much more efficient tool when the projects are larger.

Essentially, RTK trades money for time (e.g., you pay more for the equipment but it takes less time to complete the task), while post-processing trades time for money (e.g., you pay less for the equipment but spend more time to complete the task). I know I’ll get a few letters about that because there are some exceptions, but they are generally true statements.
As you see in the example above in comparing the R8 GNSS and the Epoch 25 system, “full-blown RTK systems” can carry significantly different price tags. These days, there are generally three different levels of RTK survey systems:

  1. L1-only RTK. A relatively new technology, this is an entry-level RTK survey system for under U.S. $15,000. It’s suited well for environments that are ideal GPS conditions, such as wide-open construction sites with a clear view of the sky. The distance between base and rover is generally limited to 10 km, or about (six miles).
  1. Legacy L1/L2 RTK systems. These are the traditional RTK GPS systems like the one I own and like the Epoch 25 system mentioned above. They use L2 in addition to L1, so a longer distance between base and rover is achievable. They are the traditional dual-frequency receivers. They don’t accommodate the new GPS signals being broadcast and planned (L2C and L5), nor can they utilize neither the Russian GLONASS system nor the planned Galileo system. Prices for these systems typically range from U.S. $19,000 to $35,000.
  1. Advanced GNSS RTK systems. These are the state-of-the-art RTK survey systems that utilize all signals being broadcast by GPS and GLONASS, as well as taking into account future GPS (L5), GLONASS and Galileo signals (as much as possible). These bleeding-edge systems will allow you to push the envelope as far as possible with satellite positioning. Due to the additional signals they are able to utilize, you will be able to use these systems at times when the other two can’t perform due to lack of satellite signals. Prices for these systems typically range from U.S. $35,000 to U.S. $60,000.

It’s tough to cover a topic such as this in a single column, so I’m sure I’ll visit it again. Maybe some of you will email and perhaps I can write about some specific case studies and publish some sort of purchase decision analysis for GPS/GNSS equipment. I’ve also got a few case studies I could include in such a discussion. Given the economic climate, I think this issue will be discussed often throughout 2009, at least.

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