TopCon versus Trimble

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You may ask why we chose TopCon over Trimble. Trimble is the largest GPS company, and considered the 'standard' for high-end GPS equipment.
    First, there are no technical differences between TopCon and Trimble. They both feature millimeter static accuracy, and centimeter RTK accuracy. They both use a base station and rover, with radio and satellite connection.   
    Many people purchase TopCon to access GLONASS. GLONASS is the Russian satellite configuration. Having GLONASS allows for more satellites to be accessed. Trimble representatives have suggested that there might be technical or accuracy difficulties with GLONASS. We have been unable to validate any of these statements. However, we chose not to purchase GLONASS at this time, therefore, we are receiving exactly the same information as Trimble units.   
    Finally, TopCon is able to download the data off their units in a format that is acceptable to GIS software, such as that from ESRI.  We had both Trimble and TopCon come to Crested Butte for demonstrations, and we choose TopCon for three reasons:

1.) User technicial support

2.) User interface

3.) Ease of set-up

It is our belief that the user support provided by TopCon will be more flexible and will accommodate more of RMBL user's needs.

The users interface with the TopCon unit was more smooth and compact than that of Trimble.  It is our belief that the TopCon unit will have a smaller learning curve due to this simplier user interface.

The setup for the TopCon unit was much more simple.  We chose to purchase an internal radio and battery on our base station, which decreases the number of tripods, cables, and external batteries.  We were able to choose the internal set-up due to the type of antenna that TopCon was selling.  With their internal set-up, TopCon is selling a "rubber-duck" antenna that has positive gain.  Gain is an increase in the energy emitted by an antenna over what would be produced by a standard reference antenna with the same power input.  It is also defined as the ratio of the power transmitted by an antenna in a certain direction to that which would be transmitted in the same direction if all the power supplied to the antenna was radiated isotropically.

The internal set-up that Trimble is selling is a no-gain or unity-gain 'rubber-duck'.  Unity gain/no-gain is a set-up where that is no amplification or attenuation to the radio signal.  A no-gain antenna will have decreased performance as you move away from the base station or through obstacles, which we saw during the demonstration.

2007 Note:  We have found that the user support has been sufficient for our needs.  Users learning to use the unit have found it user friendly and fairly simple.  The unit's radio has also performed excellently over long distance and through obstacles.  We rarely lose radio connection with the base.  When there are significant obstacles (trees, hills), the unit performs well in the 2-3 miles range.  Without obstacles, the rover can stay connected to the base up to 4 miles.  Based on the size and structure of our localizations, these ranges are more than sufficient.