From: Michael Sears <[EMAIL PROTECTED]> Subject: Re: GPS units and accuracy data
(snip) First, there is NO way to post correct data collected from a Garmin or Magellan unit. You are stuck with the data that you have collected. (endsnip) ----------------------------------------------- I'm afraid that I must respectfully disagree with you. Others do as well. Professor Antonio Tabernero Galán was the pioneer in the subject. Although his work was not the first to extract raw data from a Garmin GPS unit, it was the first to create software that was useable in the field and in the office. See http://artico.lma.fi.upm.es/numerico/miembros/antonio/async/ Doctor Dennis Milbert, head geodecist, National Geodetic Survey (NGS) has also produced some very nice software, including a variety for post- processing both static and kinematic data from Garmin units. He was also kind enough to work with me a few years back to modify one of his softs to use Garmin's newer line of remote sensors. I'm referring to the GPS-16, - 17, -18 and so on. Once Dr. Milbert's software converts the Garmin raw data into a RINEX file, it is also useable in many (any?) of the current packages that post- process using RINEX and SP3 files in combination. I have attempted this in a few of them, but cannot make a claim that it will work in all. Professor Galán's software is well documented, and it is able to get much, much better results than the NMEA output alone. Other people have used it more than I, and I won't get into great detail over something that I'm not extremely familiar with. These are cases of hobbyist work gone into overdrive by mathematicians obsessed with an idea. This is how some of the best technical innovations in our history have come about. There are also a few commercial applications out there as well that use handheld, single frequency raw output to post-process data and receive results in the sub-meter range. See GRINGO and PostPro for a couple of examples. I currently use DeLorme's Blue Logger to collect raw SiRF data which is able to be processed with DeLorme's PostPro. They claim sub-meter static and sub-5 meter kinematic. That is legalese, of course, and I've not had data get close to the worst-case scenario unless I was in very deep cover or the useable satellite count was at 5 or 4. My best results have been to use PostPro to convert the raw SiRF data to a RINEX file and then use Dr. Milbert's software to convert the RINEX data to a position file. Your mileage may vary. Respectfully, Frank Looper, Jr. *SLA *Semi-literate amateur.
