jpb10 / solarcalculator Goto Github PK

hello
platformIO tells me that the upgrade is not compatible with version 2.0.0
I am on mega 2560 V3, there is an incompatibility?
my version 1.03 works perfectly thanks to you.

The accuracy of the azimuth value is fine, but it isn't for the altitude, and this problem seems to only occur at the poles or so.

Location is 90°S and 0°E.
Time is 23:53:46 UTC on March 22, 2023 (1679529226)

#include <iostream>

#include "SolarCalculator.h"

int main() {
    double az, el;

    time_t time = 1679529226;
    calcHorizontalCoordinates(time, -90.0, 0.0, az, el);
    std::cout << "Azimuth: " << az << "\nElevation: " << el << '\n';

    return 0;
}

Program output

timeanddate.com (https://www.timeanddate.com/astronomy/night/@-90,0) (displayed time is UTC+13)

I am getting incorrect values for Astronomical dawn, and for both Civil and Nautical dusk. The following values are for location 33.386854212167975, -111.64819464040542 on date 3/9/2023.

Astr 5:51 (should start about 5:23, and notice it's the same as Naut)
Naut 5:51
Civil 6:20

Sunrise 6:44
Transit 12:37
Sunset 18:29

Civil 18:54 (should start about 18:30, obviously)
Naut 19:23 (should start 18:55, and notice it's the same as Astr)
Astr 19:23

Everything else above is within round-off allowance. So, very good!

The code can be viewed/run here:
https://wokwi.com/projects/358710780536496129

Could you please run your example code SunriseSunset.ino with the following numbers and see why it is giving such odd numbers?

// Date
int year = 2022;
int month = 1;
int day = 15;

// Location
double latitude  = 18.19;
double longitude = 120.55;
int time_zone    = -8;

With those figures, I get:

Date: 2022-1-15
Latitude: 18.190 Longitude: 120.550
UTC offset: -8
--
Sunrise: 0-9:0-28
Transit: 0-3:0-53
Sunset:  01:42
Civil dawn: 0-9:0-51
Civil dusk: 02:05

ESP32. Arduino IDE. Nothing changed in the library or example code except the lat/long and date values at the top.

For example, could the function calcSunriseSunset(...), and some others, make the values in UTC timestamps instead of hours of the day?

In this program, the UTC day is Nov 11, 2022, but my local date is Nov 10, 2022. When the program calculates the sunset time using the unix epoch (using my utc_now variable), it calculates the sunset at my location for the next day, not for the current date.

unsigned long utc_now = 1668127050;
calcSunriseSunset(utc_now, LATITUDE, LONGITUDE, transit, sunrise, sunset);

// Printed as seconds after midnight.
std::cout << utc_now % 86400 << '\n';
std::cout << sunset * 3600 - 86400 << '\n';

// My correction
if (sunset > 24) {
    utc_now -= 86400;
    calcSunriseSunset(utc_now, LATITUDE, LONGITUDE, transit, sunrise, sunset);

    // Printed as seconds after midnight.
    std::cout << utc_now % 86400 << '\n';
    std::cout << sunset * 3600 - 86400 << '\n';
}

Hello!

I analyzed the code and found that this line:

m[0] = jd.m + wrapTo180(ra - longitude - GMST) / 360;

Is used to calculate the transit [solar noon]. I tried adjusting it to return solar midnight , but without succes. I would add m[4] for solar midnight, but my astronomy know how is too limited for this.

Could you please tell me how to get it to return the solar midnight?

Thank you .

Best regards, Marius.

Looking at the source code, it does appear to show the values being converted from radians to degrees. The suggestion is to define an optional bool parameter to return the values in radians instead of degrees (not sure if this feature is necessary, but I wonder about losing decimal places for rad -> deg -> rad, like converting the returned double values back into radians, due to floating-point problems).

Hi, I've made some simple ports of this to Linux which are mostly printf instead of Serial.print and adding <math.h> and <stdio.h> but what I'm getting is off from what NOAA states for San Diego CA. https://gml.noaa.gov/grad/solcalc/

NOAA would say my solar elevation is 43.61 but the library calculation gives me 19.7
NOAA would say my solar azimuth is 236.3 but the library calculation gives me 100.6

The calculated sunrise and sunset are off by 2 minutes and 3 minutes compared to NOAA so pretty close.

I'm using Lat long in the library as obtained from the NOAA web page when the marker is placed at the airport on the road to Harbor Island Dr:
double latitude = 32.727219;
double longitude = -117.19665;

Any ideas on what could be causing this elevation and azimuth discrepancy?

Hello!

I have found a systematic issue:

double lat = -17.803; // fiji, nadi
double lon = 177.416;// fiji, nadi
int y = 2022;
int m = 9;
int d = 27;
calcSunriseSunset(y, m, d, lat, lon, transit, sunrise, sunset, SUNRISESET_STD_ALTITUDE, 2);

The function returns sunrise = -6.062. This is correct. However , if we set m = 10, the next month, the sunrise value jumps to 17.560. If I feed it UTC time, the date differs when the «jump» to a sunrise at 17h occurs. I tried the function with different iteration levels: 1, 5, 10... Nothing helped.

I found a similar thing happens for other locations in Fiji, and in Funafuti [Tuvalu], Apia [Samoa], Nuku'alofa [Tonga] and others. But, at different dates.

Please let me know if you can confirm the bug. Thank you .

Best regards, Marius.