It will take some time for me to add SBN or SBP support. At the same time it's easy for me to add the NMEA (i.e. the file with NMEA sentences). Would it be helpful for someone?
The NMEA contains Doppler's speed at least if GPS chipset supports Doppler's data (speed and direction). The official GPX format doesn't contain the speed field (see the set of possible fields for the GPX's way point is at www.topografix.com/GPX/1/1/#type_wptType - no speed field in GPX format at all according to that resource).
Possibly some manufacturers of GPS devices write the speed value via the fields of their own GPX extensions. If so then I can add the speed in the same way. I just need an example of such file to do that (email support@windrace.info)
Yes, very nice, the more I see of this app the more I like it.
1 point details:
moment: 00:04.35
speed: [GPS] 16 knots; 15.817 knots
pos: -32.58805°, 115.6444233°
direction: [GPS] 92.41°; 90°
sattelites: 10
HDOP: 0.86, VDOP: 1.45, PDOP: 1.68
2 point details:
moment: 00:04.36
speed: [GPS] 15.941 knots; 16.136 knots
pos: -32.5880533°, 115.6445117°
direction: [GPS] 92.26°; 92.552°
sattelites: 10
HDOP: 0.83, VDOP: 0.82, PDOP: 1.17
3point details:
moment: 00:04.37
speed: [GPS] 16.47 knots; 15.817 knots
pos: -32.5880533°, 115.6445983°
direction: [GPS] 89.11°; 90°
sattelites: 10
HDOP: 0.86, VDOP: 1.44, PDOP: 1.68
And here's the GPSResults 2 points
gps results 2sc
#286 083257 16.017
#287 083258 15.959
#288 083259 16.484
#289 083300 15.784
Very strange, the numbers are almost the same?
There's no where else on the file, that has numbers close to this, are the 2 programs are getting different numbers from the phone?
Looks the same to me
Thank you for the details. Now I see what the "Trapeze" calculation means
The WindRace's calculations are in meters per second (behind the scene). And the report's data is in the same units. Possibly I missed the tail of the number somewhere in calculations. May be one of the reasons declared before... Will check the code and write back soon.
Q: Is the "Trapeze" calculation a kind of a standard. I.e. should I use that way of calculation for best 2 sec (10sec, 100m and etc)?
decrepit, can I also ask you to write the coordinates of those three points from GPSLogit (it can help to understand the reason of the difference)
great to see someone going to such lenghts !! Thanks Arseny (and thanks Michael too for the testing !!)
The differences seen could be just lack of resolution in the files, but also could be the difference method of integration used.
GPS-Results has a number of options. It used cubic spline by default for the 2 sec and 10 sec but not sure if it is Trapezoid or Rectangular for the others. If you run that version of RealSpeed I sent you Mike you should be able to choose either Rect or Trap and work it out.
Arseny, I note when looking at the Windrace generated gpx files in notepad or wordpad the speed (and other readings) have only 1 decimal place whereas gpsBabel has about 6 or 7 (?? way overkill). I guess this is probably different from your Windrace Report calculations but maybe an extra decimal point may make things more accurate when running the tracks on 3rd party software. ie(Realspeed, GPSResults or GPSActionReplay).
Some software loggers also put out COG info and if the tracks were calculated from SOG and COG rather than positional data then I'm sure they will be far less "noisy" .
HDOP has been bandied about a lot (and some of the above 3rd party programs wont run if you don't have it) but really it is a hangover from positional trackpoint and as what most of us are interested in is speed, then the SDOP is probably more important than HDOP.
This is what I find very strange. the same data from the same phone is simultaneously sent to two programs, shouldn't this data be identical??????
Data in WindRace HTML report
1 point details: moment: 00:04.35 speed: [GPS] 16 knots; 15.817 knots pos: -32.58805°, 115.6444233°
2 point details: moment: 00:04.36 speed: [GPS] 15.941 knots; 16.136 knots pos: -32.5880533°, 115.6445117°
3 point details: moment: 00:04.37 speed: [GPS] 16.47 knots; 15.817 knots pos: -32.5880533°, 115.6445983°
Data from GPSLogit .sbp file via reelspeed.
#287,01:32:58, 115.6445117, -32.5880532, dop speed 15.959
#288, """""""59, """"""""""983, """"""""""""", """"""""" 16.484
#289, """""3:00, """".64468 , """""""""499, """"""""" 15.784
So windrace "2 point" is logit # #287 but the co-ords are slightly different, -32.5880533° for WR and -32.5880532 for logit, and speed also different 15.941 kts for WR and 15.959 for logit.
"3 Point" WR and #288 logit have the same co-ords difference and speeds 16.47 WR and 16.484 for logit.
So are the two programs interpreting the raw data differently, or is the phone sending different data to each app???
If it's two lots of data, what's the time difference? Can we combine multiple files to get a multiple Hz result? (I bet we can't)
Do we really want the same results as GPSlogit knowing the accuracy issues.
IMO we should not be comparing any of the Windrace results against logit or having it copy logit (apart from some of the functionality) less it ends up relegated as another "live reference only" program but not much good for final results.
I'll use the Pro version and run it up against the GT11 next session to compare results
I think you miss the point Alby, there's no issues with logit at all. Logit isn't the source of the accuracy issues, it's the phones raw data.
The issue is with the strange things some of the phones do.
At the moment WindRace stops the display off syndrome, but there's other problems besides that, and your phone doesn't have that problem anyway.
My Question is about how 2 apps apparently get different raw data from the same source, not about how the data is processed.
So arseny, in the comparison above, I suspect WindRace chooses which 3 points to analyse from the positional data, whereas realspeed is choosing them from the doppler data. There's a disparity in where the fastest speed is between them.
Red trace is doppler yellow positional, this is with the positional 2sec selected, when doppler 2s is selected it moves to the right.
Arseny and Mike, when I look at the Windrace gpx files with say notepad it seems to me that the <desc> gps speed o.o m/s ( km knot miles) </desc> etc is just the speed calculated from the position Lat and Long data. This is different than when you look at the track report on the Android unit itself and you can see the cleaner Doppler (ie gps unit calculated) tachyograph VS the "noisy" trackpoint data.
I removed the speed info on the exported windrace gpx file and it made no difference to the tachiograph speed (which was basically the trackpoint data with no Doppler info when looked at with Real speed.
Bit rushed at work .
Will make point clearer when have more time.
Thank you for app, Arseny.
It is great to find someone interested in our gps needs who has the skills to actually do something about it.
Whilst SDOP is "needed" supposedly for record performances personally I find the elevation/altitude more illuminating. I have a Canmore which always starts at about -400 to -250 metres elevation and the trackpoints bounce around all over the place but over about 10-15 seconds the elevation heads to near zero (+- a few metres sea level) and the trackpoints gravitate to the correct location. If I get a speed spike usually it is obvious as the elevation changes quite a bit so it is easy to tell the points are not valid. However if the SDOP info is there and easy to extract you might as well put it in.
Here's an example of why sdop values are important to us.
Yesterday I wore 2 GPSs, their results were very similar apart from the Alphas, the GT31 gave me a 23kt top score, but this alpha was the 2nd best with the GW52 and only a 22.9. The sdop values (the white dots alongside the speed graphs) show which GPS to to trust.
The GT31 has a big error margin at the gybe entry, but the GW52 has hardly any error at all.
BUT, I doubt you'll find any phones that have this data available.
If you come across any, please let us know, it would increase the value of phone data to the GTC
SDOP values are pretty meaningless for the the GPSTC. Nobody ever checks them and there's no mechanism in the posting system for rejecting tracks that are out of range or have errors. If you are going to use the values then you need to rebuild the system/software to take advantage of them. They may be great for record attempts but that's not what the challenge is about. I doubt even 1% of GPSTC speedsailors even know what they are. For the ones that spend hours poring over the data they are a bit of a giggle but making things simple and getting out on the water are more important to the majority of sailors.
Roo