I wanted to write about the weather, because nothing changes like the weather, but I didnt have the time. Then it hit me – write about time. Can anybody define time? Scientists and philosophers seem to struggle with this. I like some of the more understandable and simpler definitions. Time flies when you are having fun. Time stands still when you are bored. A stitch in time saves nine. Theres a time and place for everything. Theres no time like the present. Time and tide wait for no man. Time is money. Time will tell. Time is precious. Time is running out.
Time is not tangible. It cannot be weighed in the balance. It has no volume. It is not visible. Yet, we are surrounded by it, live in it, wear it, and see it pass us by. Time is a tool. What can we do with time and how do we spend it? It is our most precious commodity.
Order an INS (inertial navigation system) After a lot of R&D a new product arrives on the scene. Today it is the NovAtel INS built upon the STIM300 from Sensonor. This is a low cost, high performance, low noise MEMS (Micro Electromechanical System) IMU (Inertial Measurement Unit) to be installed in a new Snoopy mobile mapping system. If you dont already know, an INS is an integral part of every mobile mapping system. Theoretically an INS requires no external reference information to determine position, orientation, or velocity but we obviously use GPS to provide global geo-referencing.
Build a Snoopy. Spending a little of our precious time, our new INS is installed with our Snoopy system. A quick test is performed to make sure all is working. Everything looks fine.
Get ready to test. The next step is a quick drive through our boresight field. On the way to the site we setup the base station. This is a dual frequency GPS unit (CHC X900 to be specific) operating at 1Hz or better. A base station is necessary for most mobile mapping. The unit generally sits on a known point (or a point that will be computed using an OPUS or similar solution). The purpose of the base station is to collect ephemeris data from the GPS constellation to be used in a post processing step to compute an adjusted trajectory of our mobile system. Ephemeris data contains health and position data for each satellite in view for a particular instance in time. Without a base station our solution will not be nearly as accurate. There are alternatives to using your own base station such as a CORS station but it is almost always better to be safe than sorry use your own base station. Also, we collect at 1Hz (i.e. one record per second) or better. If less data is collected then the accuracy will begin to degrade in the final solution.
Collect some data. Now were ready for lunch. So we grab a burger and drive around the local neighborhood scanning as we go. Since the INS is new to us we want to see how it fares in reasonable GPS outage areas. We drive around some buildings and treed areas with no or intermittent GPS.
Back in the office. The data is now ready to be processed. The base station and mobile data is gathered together and quickly processed through NovAtels Inertial Explorer to generate an accurate trajectory. The boresight is computed. Finally, the point cloud is generated. Everything looks great.
To finish a normal project we might have to register the data to local survey control but in this case we just wanted to make sure everything was working and to see what happened in the GPS challenged areas. The data is impressive. Looping around with multiple passes leaves our buildings, power lines, trees, and roadway features nearly perfectly aligned. The STIM300 has proven to be a very nice unit on its first outing.
In this little experiment we spent two or three hours total building the system, collecting the data and processing the results. Time is precious. Time is billable. Time is fleeting. In our community of rapidly advancing technology, we have to be able to use our time wisely. Invest in time saving measures.
Lastly if you like a good book, read The Time Keeper by Mitch Albom. It will be a pleasant and relaxing use of your time.