We could have done a familiar "gun at"-"bs" set up that we're all so attuned to. It turned out that Bohlke had started the project that way to illustrate the capability of the software. Adding the third station made a real difference in the quality of the transformation. We tried it with two stations being observed and the results were okay, but not perfect. The geometry of the three stations was linear, being along an operating rail line and and Bohlke cautioned that such geometry is mathematically weaker than a triangular shape. We fired up the rover and proceeded to occupy the three traverse stations to do a transformation into our system, which was already in use. I really haven't been hooked up to one for a long day in the field, so I defer to those who have. The backpack was among the lightest I've used, and it seemed that it would be pretty comfortable, even if worn all day. I thought the one I was using was just fine. A very good idea it is, and I hope it is applicable to a lot of battery-powered surveying equipment.īohlke was careful to explain that the bracket for holding the SDR33 on the rover's pole was a preproduction unit, and that changes were already made. I did not ask where this idea came from, opting instead to just be thankful that somebody had the idea.
We only planned to collect enough data, maybe two hours' worth, then download back at the office. Since we were going to be within 100 meters of the base for most of our trial, the low-power option would suffice, and would enable us to probably collect data most of the day. "There are low-power and high-power options, depending on how far away the rover is from the base," he explained. "How long will the battery last?" I queried. I have to admit that the small size of the main battery on the base unit caused me some concern. Ashtech makes these units to SOKKIA specs. It was a GSR2200 real-time, dual-frequency unit, with the familiar GPS and radio antennae affair on a tripod, and the familiar cables. The base station was set up on its own point, with visibility to three traverse stations, and we began operation. Data output was to be in the project (local) coordinate system, too. I assumed that Bohlke, knowing we were in the Pennsylvania south zone, would have already input the required parameters for this area. We just took it out as, you would a regular total station, and started to survey. More experienced GPSer's will recognize that no planning was done for this GPS survey. We decided to try the real- time kinematic unit in an area that had already been conventionally surveyed. This makes it more "GPS friendly." The crew chief, Dan Hall, showed us the traverse stations and provided us with coordinate data. The busway will occupy an existing railroad right-of-way, and the terrain was more open and less hilly than a lot of the area we work in. We headed out to the Martin Luther King East Busway extension, where a crew was editing and updating existing 1986 aerial maps by picking up recent utility additions and alterations. On May 12, John Bohlke, GPS product manager for SOKKIA, flew in to Pittsburgh and was at my office first thing the next morning. Since my company already has SOKKIA total stations and SDR33s, only the new unit and GPS equipment was necessary. Usually I tell the manufacturers to send whatever software and equipment I will need for an evaluation of their product.
If you use the SDR33 data collector and are contemplating going to GPS, this month's subject may just speed up your decision making.ĭena King, at SOKKIA headquarters in Overland Park, Kansas, called in mid-April to say that sometime in May would be the time for someone to demonstrate the new SDR33, which adds the capability to use GPS and a total station with the same data collector. I had scheduled a Hands On with the company earlier, but my contacts kept putting me off while they waited for a new piece of equipment/software that has been in development for some time. This month we get to look at a well known and popular manufacturer of surveying equipment and software that has not yet been a subject of this column-SOKKIA.