I have been confused for several weeks now on the readings I get from my ALTI setting on my GWG1000. The BARO setting is 100% in agreement with the BBC weather site to the exact digit shown on there website, anything from 995 to 1028 so far. However, the ALTI geographical number for my home is 106m (348ft) according to local OS maps, but everyday it is different in wildly large amounts.
This morning apparently I now live at -37m (-121ft) but has also read as high as 224m (734ft). I have manually adjusted it more than once to my home level 106m, but it just doesn't display any degree of consistency.
If the BARO setting is accurate, what makes the ALTI setting vary so much, and if it is linked to pressure, what actual use is it to tell what level above/below sea level you actually are?