Re: [Therion] Wrong average calculation from compass/backcompass data
On Wed, May 16, 2018 at 04:45:54PM +0200, Evaristo Quiroga via Therion wrote:
> I think the problem is the average calculation formula in "thdb1d.cxx"
>
> >// check backwards compass reading
> > if ((lei->data_type == TT_DATATYPE_NORMAL) ||
> > (lei->data_type == TT_DATATYPE_DIVING) ||
> > (lei->data_type == TT_DATATYPE_CYLPOLAR)) {
> > if (!thisnan(lei->backbearing)) {
> > if (thisnan(lei->bearing)) {
> > lei->backbearing -= 180.0;
> > if (lei->backbearing < 0)
> > lei->backbearing += 360.0;
> > lei->bearing = lei->backbearing;
> > }
> > else {
> > lei->backbearing -= 180.0;
> > if (lei->backbearing < 0)
> > lei->backbearing += 360.0;
> > // calculate average of two angles
> > //lei->bearing += lei->backbearing;
> > //lei->bearing = lei->bearing / 2.0;
> > double sumx, sumy;
> > sumx = cos((90.0 -
> >lei->bearing)/180.0*THPI) + cos((90.0 - lei->backbearing)/180.0*THPI);
> > sumy = sin((90.0 -
> >lei->bearing)/180.0*THPI) + sin((90.0 - lei->backbearing)/180.0*THPI);
> > lei->bearing = 90.0 - (atan2(sumy,
> >sumx) / THPI * 180.0);
> > if (lei->bearing < 0.0)
> > lei->bearing += 360.0;
> > }
> > }
> > }
>
> I think the formula is too complicated. I purpose a simpler formula, like:
> If bearing <=180
> AverageBearing = (bearing + (backbearing -180))/2
> else
> AverageBearing = (bearing + (backbearing +180))/2
Your proposed formula gives wrong answers in some cases - consider:
bearing = 80, backbearing = 0
These give AverageBearing = (80 + 0 - 180) / 2 = -50 (equivalent to
310), but this should be 130 (average of 80 and 180).
The therion formula is attempting to average the angles by trigonometry,
which seems a reasonable approach (though probably slower than trying to
average more directly like you're suggesting). It looks essentially
correct to me, though it's a bit oddly written since cos(90 - x) is
sin(x), sin(90 - x) is -cos(x), 90 - atan2(y,x) is atan2(x,y) (possibly
+/- a multiple of 360). But if I work it out with a calculator for
236.8 and 56.8 then I do get 236.8.
If it's still not working with the declination set to zero, perhaps
you should show us a complete small example we can process to see
what is going on?
Cheers,
Olly
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Re: [Therion] Wrong average calculation from compass/backcompass data
I think Therion subtract the magnetic declination before to transfer
data Survex. Now to compare better I have put magnetic declination to 0.
declination 0.00 degrees
Data transferred to Survex by the "data.svx" file
*data normal from to tape compass clino
1 2 0.00 269.423853 0.00
1 3 2.33 236.223853 -11.40
3 4 4.51 162.623853 -32.20
4 5 12.41 0.923853 -77.70
5 6 1.95 212.073853 -17.15
You can see Therion do a wrong fore/back sight compass average
calculation. The good data average are:
1 3 236.8 -11.4
3 4 163.2 -32
4 5 1.5 -77.7
5 6 212.65 -17.15
I think the problem is the average calculation formula in "thdb1d.cxx"
// check backwards compass reading
if ((lei->data_type == TT_DATATYPE_NORMAL) ||
(lei->data_type == TT_DATATYPE_DIVING) ||
(lei->data_type == TT_DATATYPE_CYLPOLAR)) {
if (!thisnan(lei->backbearing)) {
if (thisnan(lei->bearing)) {
lei->backbearing -= 180.0;
if (lei->backbearing < 0)
lei->backbearing += 360.0;
lei->bearing = lei->backbearing;
}
else {
lei->backbearing -= 180.0;
if (lei->backbearing < 0)
lei->backbearing += 360.0;
// calculate average of two angles
//lei->bearing += lei->backbearing;
//lei->bearing = lei->bearing / 2.0;
double sumx, sumy;
sumx = cos((90.0 -
lei->bearing)/180.0*THPI) + cos((90.0 - lei->backbearing)/180.0*THPI);
sumy = sin((90.0 -
lei->bearing)/180.0*THPI) + sin((90.0 - lei->backbearing)/180.0*THPI);
lei->bearing = 90.0 - (atan2(sumy,
sumx) / THPI * 180.0);
if (lei->bearing < 0.0)
lei->bearing += 360.0;
}
}
}
I think the formula is too complicated. I purpose a simpler formula, like:
If bearing <=180
AverageBearing = (bearing + (backbearing -180))/2
else
AverageBearing = (bearing + (backbearing +180))/2
Regards,
Evaristo.
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Re: [Therion] Wrong average calculation from compass/backcompass data
Hi, I found that the error had been fixed in version 5.4.1 Therion 5.4 (5.4.1 now 2017-04-18) * bugs and issues fixed: 27. invalid compass/backcompass averaging formula But I am using the "Therion 5.4.1+6884381 (2018-04-12)", were I have found the actual bug. Evaristo. El 16/05/2018 a las 14:17, Evaristo Quiroga via Therion escribió: Hi, I have data from a survey with fore/back sight compass and clino. I have detected a Therion bug calculating the average data, comparing with the error loops with Auriga, Visualtopo, Compass and Therion. See the next compare. Example from the data in .th file: data normal from to length compass backcompass clino backclino left right up down 279.0 - 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 279.0 279.0A 2.33 236.8 56.8 -11.4 11.4 0.00 0.00 0.00 0.00 # .superficie 279.0A 279.1 4.51 163.2 343.2 -32.2 32.2 0.00 0.00 0.00 0.00 # .superficie hasta anclaje desviador 279.1 279.2 12.41 1.5 181.5 -77.7 77.7 0.00 0.00 0.00 0.00 279.2 279.3 1.95 212.2 33.1 -17.7 16.6 0.00 0.00 0.00 0.00 Data transferred to Survex by the "data.svx" file *data normal from to tape compass clino 1 2 0.00 268.348831 0.00 1 3 2.33 235.148831 -11.40 3 4 4.51 161.548831 -32.20 4 5 12.41 359.848831 -77.70 5 6 1.95 210.998831 -17.15 You can see Therion do a wrong fore/back sight compass average calculation. The good data average are: 1 3 236.8 -11.4 3 4 163.2 -32 4 5 1.5 -77.7 5 6 212.65 -17.15 The clino average seems OK. Searching in the mail-list I have found the bug was reported before. I think is not corrected since then. https://www.mail-archive.com/therion@speleo.sk/msg04660.html Regards, Evaristo. ___ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion ___ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
[Therion] Wrong average calculation from compass/backcompass data
Hi, I have data from a survey with fore/back sight compass and clino. I have detected a Therion bug calculating the average data, comparing with the error loops with Auriga, Visualtopo, Compass and Therion. See the next compare. Example from the data in .th file: data normal from to length compass backcompass clino backclino left right up down 279.0 - 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 279.0 279.0A 2.33 236.8 56.8 -11.4 11.4 0.00 0.00 0.00 0.00 # .superficie 279.0A 279.1 4.51 163.2 343.2 -32.2 32.2 0.00 0.00 0.00 0.00 # .superficie hasta anclaje desviador 279.1 279.2 12.41 1.5 181.5 -77.7 77.7 0.00 0.00 0.00 0.00 279.2 279.3 1.95 212.2 33.1 -17.7 16.6 0.00 0.00 0.00 0.00 Data transferred to Survex by the "data.svx" file *data normal from to tape compass clino 1 2 0.00 268.348831 0.00 1 3 2.33 235.148831 -11.40 3 4 4.51 161.548831 -32.20 4 5 12.41 359.848831 -77.70 5 6 1.95 210.998831 -17.15 You can see Therion do a wrong fore/back sight compass average calculation. The good data average are: 1 3 236.8 -11.4 3 4 163.2 -32 4 5 1.5 -77.7 5 6 212.65 -17.15 The clino average seems OK. Searching in the mail-list I have found the bug was reported before. I think is not corrected since then. https://www.mail-archive.com/therion@speleo.sk/msg04660.html Regards, Evaristo. ___ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
