Height Information in Locus

[eldron]

On my hike today I was playing around with the height information in Locus and got a bit confused.
I have the Locus GPS information displayed in the top bar (which includes height info) and I have the "dynamic altitude" setting activated, which shows the height information next to the crosshair (map center).
When the map center is the same as my current location, these two height values should be the same, but they are not - today the difference was around 50 meters.
My phone does not have a pressure sensor, so all values must be from GPS or a database (like the hgt files).
The map center height info must be from the .hgt files that i downloaded, as i only have that info (offline) in areas for which I have downloaded those. Am i right there?
But what is the basis for the info in the top bar? Because that value keeps fluctuating a lot, even when i don´t move.

I must say that the altitude manager is a bit confusing. Is there some explanation of it´s settings somewhere?
What is the difference between the Geoid and NMEA Correction?
Any experience on what delivers the most precise height info without a pressure sensor?

And another question - is there a better way yet to get the .hgt files than creating a point and filling in the height info? Is it possible to download the .hgt file for a whole region or country?

Edit: I found the manual for the altitude manager, but I am still nore sure about some of it... will have another look into it tomorrow, it´s too late now.

[szebenyib]

Hmm I also had problems with it. I have tried many settings, but the altitude was always different from the hgt files.
Unfortunately there is currently no option to use srtm as altitude in the settings (instead of calculating altitude from the GPS) so the altitude value is unreliable for devices like ours that do not ship with a pressure sensor.
(if I'm wrong feel free to correct me :-) )

[jusc]

In GPS Tab it seems to be the calibrated pressure hight, just testet. .
But there are other problems:
I own a phone with a pressure sensor and I don´t understand this:

1. Recording a track:  Correct hight should be 71m at target
With calibrated pressure sensor at start (56m correct)   I get 148m (more than double from 71m) at this target point..

2. Next day:
Correct hight should be 71m again at target. Non!! calibrated pressure sensor records the same start  106m this maybe ok, because the weather changed, but at the same target point it shows only 113m  ( I write only, because one day before it was 148m) instead of correct 71m.

So the correct difference should be  56 -- > 71
first  day measured                         56 --> 148
second day measured                   106 --> 113

How can this be possible?

[Menion]

Hi guys,

I'll make it short.

- "dynamic altitude" is computed from HGT files. If they are not available, it's computed online from Google Elevation API. So altitude next to center cross is always computed!
- altitude visible on other places is usually altitude from GPS after it go through whole "Altitude manager" filters.

Example at my office now
1. measured GPS value - 303m (nothing in Altitude manager enabled)
2. measured GPS, enabled automatic correction of altitude offset - 260m
3. computed altitude (dynamic altitude) - 221m

Point 2. and 3. should be same. They aren't so error in my GPS altitude is around 40m, which is expected.

- if altitude manager is confusing for you because you don't know what is difference between Geoid and NMEA, just don't use it. Altitude manager is advanced feature. What you should keep enabled is automatic correction of measured altitude (first tab) and optionally enable some stronger filter if your altitude is too noisy.

@jusc:
I don't know how this may happen. Truth is that I do not use calibration by pressure sensor, so I don't test it a lot.

There are two possible explanations
1. issue in Locus (more probable)
2. your track was quite long and condition changes a lot during that time.

Interesting should be altitude on chart measure during record compare to chart computed by HGT files

Also as I see, you use Note2? Hope you keep mind a known problem of pressure sensor on Samsung devices (if it's still there)