Pressure trend - false direction

[dreamy1]

Hello,

just found out that the trend for the pressure is displayed wrong:

float pressure_trend = WxForecast[0].Pressure - WxForecast[2].Pressure; // Measure pressure slope between ~now and later
pressure_trend = ((int)(pressure_trend * 10)) / 10.0; // Remove any small variations less than 0.1
WxConditions[0].Trend = "0";
if (pressure_trend > 0)  WxConditions[0].Trend = "+";
if (pressure_trend < 0)  WxConditions[0].Trend = "-";
if (pressure_trend == 0) WxConditions[0].Trend = "0";

In my opinion, the first line should be: float pressure_trend = WxForecast[2].Pressure - WxForecast[0].Pressure;**

[G6EJD]

If the pressure 2-hours ago was 1010 and now it is 1000 then the pressure is falling (1000-1010) and the symbol is ‘-‘

And your saying:

If the pressure 2-hours ago was 1010 and now it is 1000 then the pressure is ? (1010-1000) and the symbol is ‘+’

So which is right?

[dreamy1]

Yes, but you have not the historical data, only the actual data and the data in future. You compare the pressure at the moment (data 0) with the pressure in future (data 2).

For example: now: 1020, in 6h: 1010 -> result is +10 and positive slope - but the pressure is falling.

So it is wrong. Take a look at your picture of the display, is shows "rising" but the pressure will be falling in the next hours: https://github.com/G6EJD/ESP32-e-Paper-Weather-Display/blob/master/Waveshare_7_5_new.jpg

[G6EJD]

Which code are you referring to, your saying an image from another piece of code is wrong, and yet that code uses the OWM .trend value?

[dreamy1]

https://github.com/G6EJD/ESP32-e-Paper-Weather-Display/blob/master/examples/OWM_75_epaper_v16_7/OWM_75_epaper_v16_7.ino

The .trend value is not an OWM API value, it is generated inside the code here: https://github.com/G6EJD/ESP32-e-Paper-Weather-Display/blob/master/src/common.h

[G6EJD]

Corrected