Calculating ARCTAN in Oshonsoft

camerart · Apr 5, 2018

Hi,
I've been given an equasion by JJW, and would like to try it in Oshonsoft:
'##############################################################################
You calculate angle in radians from x, y coordinates.
Angle in degrees = radians × 180 / Pi
~ radians × 57.3
Oshonsoft has arctan function for y / x < 1
You have to calculate in eight octants ( 45 degrees )
Octants can be found from signs of x and y and from
value of y / x if it is less or greater than one.

For example, if North is 0 degrees and clockwise direction:
0 - 45 degrees x / y < 1 and x > 0, y > 0
angle = arctan( x / y ) × 57.3

45 - 90 degrees x/y > 1 x >0 y>0
angle = 90 - arctan( y / x ) × 57.3
etc ...

Angle, x and y are floating point variables
'#################################################################################
Is this correct?

Between 0° to 45°
If x/y < 1 then
If x >0 then
If y > 0 then
angle = arctan( x / y ) × 57.3
ENDIF
ENDIF
ENDIF

Corrected.
Cheers, Camerart.

jjw · Apr 5, 2018

It is not correct.
Between 0-45 , x < y
Follow the example I gave.

The arctan function in Oshonsoft is not accurate.
The error is over 4 degrees near arctan(1)

You can use the approximation which was used in the thread 1 - 1.5 year ago:
Atn(x/y) = x/y / (1+0.285125(x/y)^2)
when x/y <= 1
Accuracy is better than 0.3 degrees

camerart · Apr 5, 2018

jjw said:
It is not correct.
Between 0-45 , x < y
Follow the example I gave.

The arctan function in Oshonsoft is not accurate.
The error is over 4 degrees near arctan(1)

You can use the approximation which was used in the thread 1 - 1.5 year ago:
Atn(x/y) = x/y / (1+0.285125(x/y)^2)
when x/y <= 1
Accuracy is better than 0.3 degrees

Hi J,
When you say "Follow the example I gave" I presume you mean the one in #1, is this correct?
If so, then that was my attempt to write the first line of it. I don't understand the language your example is written in.

You say I can use the approximation from 1.5 years ago, but it has ATN, will it work in Oshonsoft?

(I apologies for being slow on my understanding)

C.

jjw · Apr 5, 2018

It is OK now after the change x/y < 1
If x/y < 1 can be written if x<y

The first example 0-45 degrees.
x, y and angle are floating point variables

If x < y then
If x>0 AND y >0 then ''' have not tested if this is ok
angle = arctan(x/y)*57.3
endif
endif

jjw · Apr 5, 2018

camerart said:
Hi J,
When you say "Follow the example I gave" I presume you mean the one in #1, is this correct?
If so, then that was my attempt to write the first line of it. I don't understand the language your example is written in.

You say I can use the approximation from 1.5 years ago, but it has ATN, will it work in Oshonsoft?

(I apologies for being slow on my understanding)

C.

ATN is just a name for the approximation function, which is defined in your program.
You can use any name which is not a reserved word in Oshonsoft.
For example arcustanget or whatever.

camerart · Apr 6, 2018

jjw said:
It is OK now after the change x/y < 1
If x/y < 1 can be written if x<y

The first example 0-45 degrees.
x, y and angle are floating point variables

If x < y then
If x>0 AND y >0 then ''' have not tested if this is ok
angle = arctan(x/y)*57.3
endif
endif

Hi J,
Can this section be used independantly?
I tried it and it complies ok, but only gives '0'
I presume the section shown as 2'S COMPLIMENT CALC IS NEEDED?

Note: I've just seen your later comment below, so another reply on it's way.
C.

jjw · Apr 6, 2018

Arctan() wants floating point ( single) variables.

camerart · Apr 6, 2018

jjw said:
Arctan() wants floating point ( single) variables.

Hi J,
Arctan is an Oshonsoft reserved word.
I'm using 'arctn' as suggested, which isn't a reserved word.

This line: azi = arctn(x_raw / y_raw) * picalc '57.3 'ARCTN Not reserved word
gives this error. Attached.

NOTE: Oshonsoft has floating point SINGLEs. I've DIMed 'arctn' and 'picalc' (57.3) as SINGLE.

C.

jjw · Apr 6, 2018

What is picalc?
Still x_raw, y_raw should be floating point.

camerart · Apr 6, 2018

jjw said:
What is picalc?
Still x_raw, y_raw should be floating point.

Hi J,

Will you clarify my questions in #6 please?

azi, X, Z, Y_raw and picalc all DIMed as LONG

I haven't been able to add 57.3 into the program, so I tried 'picalc' = 57.3. It didn't work!
EDIT: ERROR!! LONG is a mistake SINGLE should be used in some of the cases.
C.

jjw · Apr 6, 2018

2's complement is needed.
Floating point for x and y is needed, because if you divide x by y and x < y the result is zero when x, y are integers.

camerart · Apr 6, 2018

jjw said:
2's complement is needed.
Floating point for x and y is needed, because of you divide x by y and x < y the result is zero when x, y are integers.

Hi J,
Ok, thanks.

I found that using 'Const pi = 3.14159' and 'DIM picalc as SINGLE' and 'picalc = 180/pi' Compiles.

At the moment this section 0 to 45 is compiling, but not giving sensible results, so I'll recheck everything.

Will this section 0 to 45° work on it's own?

C.

jjw · Apr 6, 2018

camerart said:
Hi J,
Ok, thanks.

I found that using 'Const pi = 3.14159' and 'DIM picalc as SINGLE' and 'picalc = 180/pi' Compiles.

At the moment this section 0 to 45 is compiling, but not giving sensible results, so I'll recheck everything.

Will this section 0 to 45° work on it's own?

C.

What kind of results you get ?
Give some examples with x, y and the result.

camerart · Apr 6, 2018

jjw said:
What kind of results you get ?
Give some examples with x, y and the result.

Hi J,
Here are the DIMs and the section of program.

Since changing X, Y_raw to SINGLEs from WORD, I'm getting AZIMUTH = 0.0 in all directions.

Looking at the 5110 screen, the YWORD shows nothing.

C.

camerart · Apr 6, 2018

Hi J,
I tried changing Y_RAW back to WORD, and it now shows correctly on 5110 Scn, and AZIMUTH now shows '-- numbers.

I can see the problem. There needs to be some kind of intermediate set of words, between WORDs and SINGLEs.
C.

jjw · Apr 6, 2018

I don't see any arctan function in the program?
x and y as arguments to the function should be singles unless you will calculate with longs or words and handle all scaling back and forth.

jjw · Apr 6, 2018

Convert the x_raw, y_raw and all variables needed in calculation of arctan to singles.
It is much easier to calculate with them.

jjw · Apr 6, 2018

You have defined x_raw, y_raw as single, but use x_raw.hb x_raw.lb ??
Use x_raw ... as word, x as single and after reading x_raw and making 2's complement
x = x_raw
same for y and then calculate arctan

jjw · Apr 6, 2018

camerart said:
Hi J,
I tried changing Y_RAW back to WORD, and it now shows correctly on 5110 Scn, and AZIMUTH now shows '-- numbers.

I can see the problem. There needs to be some kind of intermediate set of words, between WORDs and SINGLEs.
C.

No intermediates are needed.

camerart · Apr 7, 2018

Hi J,
Firstly (following #2 and#5) do I use 'arctn' which is my none Oshonsoft reserved word, or Arctan which is an Oshonsoft function?

This does compile: azi = Arctan(x_raw / y_raw) * picalc '180/pi

This doesn't compile: azi = arctn(x_raw / y_raw) * picalc '180/pi

The x and y_raw HB and LB are used because the Compass module is READ in 6x BYTEs, also I use them to show the BYTEs as they change on the screen.
EDITED.

C.

Calculating ARCTAN in Oshonsoft

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