On 11/24/13 4:23 AM, Didier Juges wrote: > The Thunderbolt uses single precision floating point and digital filtering for temperature so yes, you are going to see values like this. This is not unusual (precision clearly out of step with accuracy), like the HP network analyzers returning gain in dB with 4 decimals at microwave frequencies. > Not sure what your point is? > Should Lady Heather pretend to know better and muck with what's sent by the receiver? > I prefer not but it's a matter of opinion. > > Didier KO4BB > > > David J Taylor <david-taylor@blueyonder.co.uk> wrote: >> I hope no-one believes all the decimal digits shown in that >> screen-shot! It >> seems to me that it would be better if more realistic values were >> presented! >> >> 37.808842 °C - really! >> Often it's useful to report all the digits used in the calculation, so you can reverse it back to the original, no doubt, limited precision fixed point number.

On Sun, Nov 24, 2013 at 7:13 AM, David J Taylor < david-taylor@blueyonder.co.uk> wrote: > The Thunderbolt uses single precision floating point and digital filtering > for temperature so yes, you are going to see values like this. This is not > unusual (precision clearly out of step with accuracy), like the HP network > analyzers returning gain in dB with 4 decimals at microwave frequencies. > Not sure what your point is? > Should Lady Heather pretend to know better and muck with what's sent by > the receiver? > I prefer not but it's a matter of opinion. > > Didier KO4BB > =============================== > > Oh, if that's what the Thunderbolt sends, then that's what should be > reported. I hadn't appreciated that. Makes you wonder why the designers > did that, though. > Oh, the answer to that question is easy. They knew that they had to produce a function to convert 32-bit floating point numbers to decimal representation in ascii for transmission over the serial port. But it would require additional code to round off the numbers to desired precision. And then they would have to decide what the proper resolution should be for each value. So I would have done the same thing they did. > > More modern equipment I've seen uses (for example) integers to report dB x > 10, so tenths of a dB resolution. I do see computer temperature sensors > reporting in millidegrees, with an accuracy of +/- 2°C! > Sure the accuracy may be off but if the repeatability is good the high precision with reduced accuracy is still useful for calculations in a control loop. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 brian@lloyd.com +1.916.877.5067

			Attila Kinali

On Thu, 21 Nov 2013 19:47:03 -0500 "Dale J. Robertson" <dale@nap-us.com> wrote: > An interesting technique for improving the accuracy of single band gps is > embodied in an open source program/project called rtklib. > Essentially it uses one GPS receiver in a fixed location that has been very > carefully surveyed (gps reported location averaged over a long period) as a > phase reference. > The roving receiver then uses the raw phase data from the base to subtract > errors in the location of the rover. > 10 cm accuracy is achievable in real time using consumer grade GPS > receivers, If you go non-realtime you can acheive sub-cm accuracy. A project i was involved with at the side lines uses LEA6-T modules and records the phase data. Processing over 4-6h data gives then something in the range of 4mm accuracy. Attila Kinali -- 1.) Write everything down. 2.) Reduce to the essential. 3.) Stop and question. -- The Habits of Highly Boring People, Chris Sauve