Barometer and pressure once again

[Tomasz Lewicki]

I'm trying to sort out barometer and pressure values. I own HP1001 clone. Internal T/H/P sensor was calibrated with my friends certified barometer before. Currently it sensor shows absolute pressure value 936,7 hPa and it almost perfectly (+/- 1 hPa) aligns with very accurate numerical forecast for my location. Same meteogram show also relative pressure 1007 (+/- 1 hPa) for my location. METAR for nearby (43 km) airport shows 1008 hPa.

Relative pressure displayed by my HP1001 is about 20 hPa higher than absolute - obviously too low value because I'm located about 550 m AMSL.

When calculated by Weewx itself ("software" option enabled in weewx.conf), my weather station shows 1001 hPa - still too low. Of course I checked location setting and AMSL value and unit - in my opinion they are properly set. Should I change something in weather station settings? I can set only coordinates, not the AMSL height. 

[Rainer Lang]

yes - why not calibrate your console first
when you see that the offset between absolute and relative pressure for your location used is wrong, just adjust it 😎
the the first basic step I'd say

even though, when your absolute (=local) pressure reading is correct, and your have the weewx option in weewx.conf set to software, weewx should calculate the proper relative value (taking into account the average temperature of the past 12 hours afaik).

"When calculated by Weewx itself ("software" option enabled in weewx.conf), my weather station shows 1001 hPa - still too low. " - I guess what you want to say is not that your station shows too low a value, but that weewx caluclates too low a value for your station (these are two different things) - your station will continue to show what its reads and what it is calibrated for. Weewx has no feedback to you station.

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[Greg Troxel]

Tomasz Lewicki <sta...@poczta.onet.pl> writes:

> I'm trying to sort out barometer and pressure values. I own HP1001 clone.
> Internal T/H/P sensor was calibrated with my friends certified barometer
> before. Currently it sensor shows absolute pressure value 936,7 hPa and it
> almost perfectly (+/- 1 hPa) aligns with very accurate numerical forecast
> for my location. Same meteogram show also relative pressure 1007 (+/- 1
> hPa) for my location. METAR for nearby (43 km) airport shows 1008 hPa.
>
> Relative pressure displayed by my HP1001 is about 20 hPa higher than
> absolute - obviously too low value because I'm located about 550 m AMSL.

I have not fully dealt with this and I don't know your hardware, but I
have thought about it a lot. But some advice:

do not just twiddle without understanding

a station that reports other than station pressure and doesn't let you
enter elevation/altitude (distance above the nominal 0 level at sea
level ish*) is designed wrong. The station might be near the ground
and it might be in an upper floor. There is no way to know elevation
from horizontal location.

use the proper terms when discussing and thinking.
https://github.com/weewx/weewx/wiki/Barometer,-pressure,-and-altimeter

understand the data flow of your station. surely it is measuring
station pressure, but often it will convert to one of the others and
then that is all you can extract.

understand that weewx can convert, but needs to have altitude

understand that measuring altitude is quite difficult at the 1m level,
and that 1 hPa is about 8.3 m. reading a value from a non-RTK GNSS
(GPS, Galileo etc.) is just not that accurate.

There is a calibration for the sensor, which is perhaps adequately
modeled as an offset in station pressure.

you then have to get altitude right, and calculations right

by adjusting altitude it is sort of like adjusting the station
pressure offset. This may be the best you can do, depending on what
the unit reports and how it gets altitude.


Overall, I suspect your unit has got a bad elevation value for where you
are somehow, and you have made it display station pressure correctly.
It seems to think you are ~160m lower than you are.

I would look on forums to find out how your unit is supposed to work.

Or get a BME280, calibrate that with your friend's instrument (they are
pretty repeatable but have multi-hPa absolute calibration), and use that
as station pressure instead, and have weewx do it is software.



* the meaning of elevation remains unclear. Probably the height
according to your country's national vertical datum is appropriate.
If you are really in .pl, that's probably in EVRF2007, but even if
it's not, they are almost all very close.

[Greg Troxel]

from the wiki page I sent

For example, the FineOffset consoles can display either the station
pressure (called 'absolute' pressure) or the station pressure plus an
offset (called 'relative' pressure). T

So Fine Offset equipment just does pressure badly.

So get station pressure into weewx, do software from that, and tape over
the "relative pressure" display on the console so nobody can see it!

[Tomasz Lewicki]

Rainer, Greg,

thank you both for thoughts and hints. Indeed, when I wrote "When calculated by Weewx itself ("software" option enabled in weewx.conf), my weather station shows 1001 hPa - still too low", I meant what Weewx calculates and show on my webpage, not on console's display - display is completely wrong in my opinion.

According to design of PWS, I own Ambient Weather WS-1001-WiFi clone. I use HP-1000 driver. I don't know if it is designed wrong or not, but I know that many people still use it.

Manual for my station say "To determine the relative pressure for your location, locate an official reporting station near you (the internet is the best source for real time barometer conditions, such as Weather.com or Wunderground.com), and set your weather station to match the official reporting station." I understand it, I should calibrate PWS entering proper value from METAR for example.

But I still don't understand why Weewx, using "software" option for calculating the sea-level (relative) pressure, shows too low value. As I said, my station location AMSL in weewx.conf is "altitude = 550, meter" (and for me it is neglible if it is 552 or 560; it is fraction of 1 hPa). So the only way to show "real" value is to calibrate the relative pressure (barometer in Weewx's terms) on the station's display and set "prefer_hardware" in weewx.conf? I'm really confused.

Or maybe I have some units in weewx.conf messed up? I use metric system so I entered meters when it was possible.

[Greg Troxel]

Tomasz Lewicki <sta...@poczta.onet.pl> writes:

> thank you both for thoughts and hints. Indeed, when I wrote "When
> calculated by Weewx itself ("software" option enabled in weewx.conf), my
> weather station shows 1001 hPa - still too low", I meant what Weewx
> calculates and show on my webpage, not on console's display - display is
> completely wrong in my opinion.

Thanks for clarifying. This is tricky so we need to be 2x clearer than
we think we need to be :-)

> According to design of PWS, I own Ambient Weather WS-1001-WiFi clone. I use
> HP-1000 driver. I don't know if it is designed wrong or not, but I know
> that many people still use it.

True that people use it but that doesn't mean it really works, and the
path to getting useful data out is to understand how it is wrong so that
can be worked around.

> Manual for my station say "To determine the relative pressure for your
> location, locate an official reporting station near you (the internet is
> the best source for real time barometer conditions, such as Weather.com or
> Wunderground.com), and set your weather station to match the official
> reporting station." I understand it, I should calibrate PWS entering proper
> value from METAR for example.

I assume -- but you didn't say -- that "set your weather station to
match" means "do some UI adjustment with up/down so that the thing the
weather station displays as 'relative' is the same value as the
barometric pressure from a nearby official station". That's what I
would expect.

What is going on then is:

there is an absolute pressure measurement device in the console, which
is
a) probably not super well calibrated (might be within 2-3 hPa,
might be a bit better - we simply don't know so far)
b) at some unknown altitude (even if you know it, the console
doesn't), so the console has no way to do the proper reduction to
barometric pressure.

console takes that value and adds a constant offset. You can change
that in the UI process above. This is a hack to get something that is
more or less good enough for stations in this price/performance class,
approximating the barometric pressure formula by "add K".

What I still don't know is what value is sent to the computer. The
uncalibrated station pressure? The 'relative' pressure, aka
"station+K, for the entered K"? Both? I think you don't know this
either, and we can't figure out what's going on and what to do until
we understand it.

> But I still don't understand why Weewx, using "software" option for
> calculating the sea-level (relative) pressure, shows too low value. As I

Of course we don't understand, because we don't know what is being
reported and how the console adjustment procedure affected it. We also
don't know what kind of errors the sensor has.

Sea-level pressure is not "relative" pressure. Sea-level pressure
normally means "barometric pressure", which is station pressure reduced
with temperature measurments. (There is also "altimeter pressure",
which is station pressure reduced with a standard atmosphere profile,
but that's close to barometric and you are a long way from worrying
about that difference.)

There is no such thing as "relative pressure", only "fine offset
mislabeled as relative but is actually station pressure + K". As I said
before, you should understand the proper terms and use them carefully,
if you want to get correct answers.

> said, my station location AMSL in weewx.conf is "altitude = 550, meter"
> (and for me it is neglible if it is 552 or 560; it is fraction of 1 hPa).
> So the only way to show "real" value is to calibrate the relative pressure
> (barometer in Weewx's terms) on the station's display and set
> "prefer_hardware" in weewx.conf? I'm really confused.

You are confused because you don't know what's coming over the wire from
the station, and you don't know if the station pressure is
miscalibrated.

> Or maybe I have some units in weewx.conf messed up? I use metric system so
> I entered meters when it was possible.

Maybe, but I don't think we can conclude that.

First, read the driver "fousb.py" in the sources. Even if you don't
know python, look for "pressure calculations" in the code and read the
comment.

Looking at the driver, it looks like "abs_pressure" is the only thing
actually read from the station.

I would suggest:

look at your database and the values for station pressure ("pressure")
and barometric pressure. Maybe change your skin to also graph station
pressure.

run for an hour with barometer set to prefer_hardware, and for an hour
with it set to prefer_software. Or longer, doesn't matter. See how
pressure/barometer relate and if it is any different. I am just not
seeing a hardware path for barometer.

probably conclude that the behavior is the same, but that
prefer_software is cleaner because it documents what happens.

run for an hour with your newly-concluded-as-right prefer_software
setting and the console as is.

go into cal mode on the console and set the pressure 5 hPa higher than
it is, 50 clicks up assuming 0.1 hPa. Yes I know this is wrong but
it's an experiment.

run for another hour

50 clicks back down in cal setting, and a third hour

now look at the dB and examine (graph even better) station pressure
and barometer. I more or less expect either:
- station pressure was steady, and barometer also
- station pressure changed 5 hPa up and back down, and barometer
also roughly 5
This tells you if the console calibration is just changing the console
display, or if it affects the station pressure reported to the
computer.

Probably, the path to getting this right is:

if station pressure as reported to weewx is unchanged by console
calibration, calibrate console to match barometer from nearby official
station, then ignore console relative to weewx and consider it just
for local humans. Then, look at station pressure in weewx and compare
to your friend's calibrated baromoeter and figure out the offset. It
should be only a few hPa. Put this in a StdCalibrate section, which
is correcting the hardware error in your pressure sensor. If it's
more than a few hPa, post actual data.

If station pressure as reported to weewx is modified as you change
console calibration, then have your friend with a calibrated barometer
(which can measure station pressure) visit and adjust the console
calibration to match that reading. This will abuse the console's
mechanism (intended to badly calculate barometric pressure) instead as
a mechanism to calibrate out the sensor error. Weewx will get correct
station pressure, and the console will show station pressure, not
"barometric pressure".

Now, weewx's station pressure from the hw is correct, and if your
elevation is right the barometric pressure should be close to the
nearby official station. Examine the barometer vs the official
station and see how it tracks. Please report back!



I will speculate wildly a few ways

1) The pressure reported by the console to weewx is changed by the
calibration process, and the sensor itself is ok

You say 550m, and for 1013.25 hPa at 0 m elevation and 20 C,
station pressure should be around 950 hPa. If the calibration
causes the device to report 1013.25, and then weewx calculates, it
should get about 1080 (which is impossibly high, but is what
barometric pressure would be if station pressure at your altitude
was 1013.25 hPa.

2) The pressure reported is not changed, but the sensor reads low.
weewx is getting a wrong station pressure.


Next message, please give actual pressure values, rather than "too
high", as this is too hard to follow. Include all of, from the same
time:

if you have any stdcalibrate lines
elevation of console (550m so far)
'relative' display on the console
station pressure from another device physically at your console
barometric pressure at official station
station pressure at official station
official station's altitude
"pressure" and "barometer" from the weewx database

Greg

[Rainer Lang]

to calibrate your WS-1001 (Ambient version of the FineOffset/EcowittWH24 outdoor array and the WH1080 console) you could just follow the instructions in https://www.wxforum.net/index.php?topic=40730.0 chapter 6
determine the offset and enter it accordingly (either an offest of change the value, whatever the console wants --> manual).

METAR, airport etc. are secondary approaches for refinements which you may or may not want to follow. There are lengthy and complex treatises on that topic in the same forum, from simple to highly complex.

[by the way, if you have a European or international "version" of the Ambient WS-1001 and call this a clone version, then that's very strange wording as Ambient is the clone and not Fine Offset/Ecowitt = the manufacturer]

but true, weewx should come to a proper result - and unless your station also reports wrong absolute pressure (= local pressure) - or you display the wrong variable/observation in your skin, then something is wrong with weewx. Rather unlikely.
Did you read the barometer topic in the weewx online documentation ?

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[Tomasz Lewicki]

Thank you for advice. I will follow the guide you pointed me to.

[Tomasz Lewicki]

W dniu 31.08.2023 o 16:55, 'Rainer Lang' via weewx-user pisze:

> to calibrate your WS-1001 (Ambient version of the FineOffset/EcowittWH24
> outdoor array and the WH1080 console) you could just follow the
> instructions in https://www.wxforum.net/index.php?topic=40730.0 chapter 6
> determine the offset and enter it accordingly (either an offest of
> change the value, whatever the console wants --> manual).
>
> METAR, airport etc. are secondary approaches for refinements which you
> may or may not want to follow. There are lengthy and complex treatises
> on that topic in the same forum, from simple to highly complex.
>
> [by the way, if you have a European or international "version" of the
> Ambient WS-1001 and call this a clone version, then that's very strange
> wording as Ambient is the clone and not Fine Offset/Ecowitt = the
> manufacturer]
>
> but true, weewx should come to a proper result - and unless your station
> also reports wrong absolute pressure (= local pressure) - or you display
> the wrong variable/observation in your skin, then something is wrong
> with weewx. Rather unlikely.
> Did you read the barometer topic in the weewx online documentation ?

I'm back and starting my reply from Rainer's last question. Yes, I've
read this topic:
https://github.com/weewx/weewx/wiki/Barometer,-pressure,-and-altimeter
on the very beginning. I use only 'pressure' and 'barometer' terms
below, according to definitions from wiki.

So, I'm even more confused than before. I've made the calculations with
the calculator listed in https://www.wxforum.net/index.php?topic=40730.0
(direct link: https://keisan.casio.com/exec/system/1224575267 - BTW they
will close at September 20) with my current conditions (pressure 944.5
hPa, temperature 20*C, height of sensor 560 m AMSL) and got result
1007.8 hPa - this is perfectly equal to what I see on my webpage -
1007.7 hPa calculated by Weewx algorithm (difference of 1/10th of hPa is
neglible). I recall that I use 'software' option in weewx.conf for
'barometer' but 'prefer_hardware' for 'pressure'.

But very accurate numerical forecast for my location *and* METAR for
EPWR airport shows 1015 hPa. So I need to "collect" additional ~7 hPa
(1015 from METAR minus 1007.8 from Weewx calculations). Does it mean I
should:

a) add whole calculated offset - ~70 hPa (1015 from METAR minus ~945 of
absolute pressure) - in my PWS console

or

b) add smaller offset - 63.3 hPa (1007.8 calculated by Weewx minus 944.5
read by sensor) PLUS use relevant section in weewx.conf:

# This section can adjust data using calibration expressions.

[StdCalibrate]

[[Corrections]]
# For each type, an arbitrary calibration expression can be given.
# It should be in the units defined in the StdConvert section.
# Example:
foo = foo + 0.2

to incorporate "rest" of offest (METAR value minus barometer value
calculated by Weewx):

[StdCalibrate]
[[Corrections]]
barometer = barometer + 7.2

I only need confirmation that I'm going in right direction - or opposite.

[gszla...@gmail.com]

Perhaps I can help as I own both an Ambient and Ecowitt weather station.

I recently did a major rewrite of an older Ecowitt barometer calibration procedure  and the new procedure should work with any Fine Offset manufactured device with a barometric sensor.

Some basics regarding this equipment:

- there are no algorithms in firmware to calculate (M)SLP or Altimeter. We know that WeeWX has the algorithms we need to calculate those values therefore you need an accurate station pressure to send to WeeWX.

- Fine Offset defines everything in terms of pressure so if you wish to enter your elevation you need to know your standard atmosphere pressure for your elevation(actually what you want to calculate is the pressure difference between your location and sea level).

- Fine Offset weather stations employ a fixed offset system to estimate/calculate Altimeter(QNH) or MSLP (QFF)

- unfortunately, MSLP can not be reliably be calculated using a simple fixed offset. In reality, the MSLP offset is actually variable - unless you live close to or at sea level. Therefore, your best bet for calibration purposes is to match the REL (relative pressure) with a close by airport's Altimeter reading. In Europe it might be better to match your government weather service to obtain decimal point QNH values. Otherwise, you are stuck with integer value QNH in the METAR reports.

The procedure is too  lengthy to post here so here's the link to read: https://www.wxforum.net/index.php?topic=45601.msg462080#msg462080

Instead of calculating the REL offset manually, I have suggested an alternative calculator in order to calculate the REL offset (elevation offset) directly.

The shortest and perhaps easiest way to calibrate is to use the REL offset calculator and then adjust your ABS value until ABS matches Altimeter or QNH.

Once you are calibrated, you will have/should have an accurate station pressure(ABS value) to use for WeeWX. No need to employ correction offsets in weewx.conf.

Personally, I calibrate at least yearly with my own reference barometer that I made with a Bosch BMP390 and a raspberry pi. The Fine Offset barometer sensors are getting long in tooth and are particularly "drifty" (long term drift).

PS. At 550m elevation your REL offset (REL minus ABS) should be 64.35 hPa. Your display console should show that your REL reading on the display is 64.35 (64.3 rounded) is ALWAYS higher than your current live ABS value. Once you’ve done that step, you adjust the ABS value until your REL value matches the Altimeter/ QNH of the station you are comparing to.

[Greg Troxel]

Tomasz Lewicki <barbap...@gmail.com> writes:

> I'm back and starting my reply from Rainer's last question. Yes, I've
> read this topic:
> https://github.com/weewx/weewx/wiki/Barometer,-pressure,-and-altimeter
> on the very beginning. I use only 'pressure' and 'barometer' terms
> below, according to definitions from wiki.
>
> So, I'm even more confused than before. I've made the calculations
> with the calculator listed in
> https://www.wxforum.net/index.php?topic=40730.0 (direct link:
> https://keisan.casio.com/exec/system/1224575267 - BTW they will close
> at September 20) with my current conditions (pressure 944.5 hPa,
> temperature 20*C, height of sensor 560 m AMSL) and got result 1007.8
> hPa - this is perfectly equal to what I see on my webpage - 1007.7 hPa
> calculated by Weewx algorithm (difference of 1/10th of hPa is
> neglible). I recall that I use 'software' option in weewx.conf for
> 'barometer' but 'prefer_hardware' for 'pressure'.

This confirms that weewx's calculation matches the web calculator, that
IF your station pressure is 944.5 hPa then the barometric pressure is
1007.7 or .8 hPa. It has ZERO information about whether the station
pressure measurement is accurate.

> But very accurate numerical forecast for my location *and* METAR for
> EPWR airport shows 1015 hPa. So I need to "collect" additional ~7 hPa
> (1015 from METAR minus 1007.8 from Weewx calculations). Does it mean I
> should:

This means that it is likely that the station pressure at your location
is about 7 hPa higher than the sensor reads.

> a) add whole calculated offset - ~70 hPa (1015 from METAR minus ~945
> of absolute pressure) - in my PWS console

This will result in wrong station pressure readings, because you are
using the console to go from wrong station pressure to fake barometric
pressure. I would advise against this.

> or
>
> b) add smaller offset - 63.3 hPa (1007.8 calculated by Weewx minus
> 944.5 read by sensor) PLUS use relevant section in weewx.conf:

This is confusing, but if weewx is getting 1007.7 hPa and the weather
service says 1015.0 *AND* you are sure your elevation is right, then
this means there is a 7.3 hPa error in the station pressure sensor.
That's a lot, but this is not professional equipment.

(Actually, I think the reduction is not linear, so this is strictly
slightly messier, but probably not relevant at the 0.1 hPa level.)

> [StdCalibrate]
> [[Corrections]]
> barometer = barometer + 7.2

Almost. The problem is that pressure is wrong. Barometer is calculated
and given correct pressure and correct altitude will be correct.

So instead:

pressure = pressure + 7.2

to fix that instead. After you do this, look at your barometric
pressure readings and the official ones over time and see how it tracks.
You may decide to change to 7.3 or 7.0 or something.

> I only need confirmation that I'm going in right direction - or opposite.

We talked about this earlier, but given that 1 hPa is about 8.3m, if
your elevation is 8.3 m too high, or if your pressure sensor is 1 hPa
too low, the two situations look the same, and you basically can't tell
them apart.

So on one hand, a 7 hPa error and a 58m elevation error are the same
thing, in terms of barometric pressure. But on the other hand, in one
case your station pressure is right, and in the other tit is not.



It would be interesting to hear from others. My experience with Davis,
2x BME280 and a BME680, a basic casio watch with pressure esnsor, and
one other not-very-expensive sensor is that most agree in a 1-2 hPa
range, they cannot in general be believed to better than 1 hPa and it is
rare, perhaps not in my data set, to be 3 hPa off. So 7 is odd. But I
do not have epxerience with Fine Offset stations. Still, I find it
surprising.

I would love to hear from people with Fine Offset stations that have
made careful measuremennts of station pressure calibration.

[gszla...@gmail.com]

No wonder the OP is confused.

In Europe, METARs generally don’t have SLP, they have QNH stated as a “Q code” in the actual METAR report. An Altimeter /QNH reading of 1022 would be Q1022 in the METAR report.

So typically, QNH > QFF when current or average outside temps are greater than the ISA temp for his elevation. That is the reason why the OP remarks that he is “missing” 7 hPa:

[I]> METAR for  EPWR airport shows 1015 hPa. So I need to "collect" additional ~7 hPa
> (1015 from METAR minus 1007.8 from Weewx calculations)[/I]

The OP is smarter than us because WeeWX SLP is 1007.8 and Altimeter/QNH = 1015.
Two different things entirely!

So let’s take a step back and try this again. We want to match Altimeter/QNH.

1. The OP is trying to calibrate by matching QNH at airport (EPWR)
2. You need to use an Altimeter calculator or ISA calculator, not a SLP calculator.

Let’s redo the REL offset for a 560m sensor elevation:

1013.25 – 947.760 = 65.49 (65.5 rounded)

The 947.76 is the fixed ISA pressure for any 560m elevation. You can use a standard atmosphere calculator or Altimeter calculator to calculate it.

Therefore, for a 560m elevation, QNH must always be 65.5 hPa higher than whatever the Fine Offset station pressure is at the moment or looking at it from a sea level perspective, station pressure must be 65.5 hPa lower than QNH.

EXAMPLE:

If EPWR is showing Q1022 then:

1022(REL) – 65.5(REL offset) = 956.5 (ABS) station pressure.
i.e. REL= QNH at airport minus your offset = station pressure at your location (560m).

To calibrate, you can either:

1. Set REL = 1022 and set your ABS = 956.5.

or

2. Add 65.5 to your existing ABS value and then compare the REL value on your display to the QNH value at the airport. Adjust the ABS value up or down until the REL display is the same as QNH as the airport. ABS and REL on your display move lock-in-step. To change the REL value, you have to change the ABS value. REL must always show to be 65.5 higher than your current live ABS reading. There will be a lot of button pushing involved, but make sure the “spread” or pressure difference between REL and ABS is always 65.5.

The first method is obviously a shortcut method. It is the simplest, and you still have to lookup your ISA pressure for your elevation, but you won’t learn much about the process.

The second method is the method I usually recommend. I am assuming the OP is configuring his barometer on a display console and must be using the ABS/REL system instead of the offset system.
The Fine Offset manufactured WiFi gateways use a different system. They are a display-less console that uses a ABS offset/REL offset system.

If the OP is still running into calibration snags, I would encourage him to post his quesion at wxforum.net in the Ambient/Ecowitt/Fine Offset clone forum.

[Tomasz Lewicki]

W dniu 3.09.2023 o 14:02, gszla...@gmail.com pisze:

First of all, *huge* thanks for taking your time and claryfing whole
process in detail. In the meantime, before you wrote your instructions,
I used your previous tips
(https://www.wxforum.net/index.php?topic=45601) and done calibration
process. Of course I can't be sure I got now "real" values but - as you
have noticed - my console doesn't allow entering the offset (which in my
opinion is much more instructive way than just entering REL and ABS
values). I have to check once more ABS value with certified barometer.

By the way: I'd be grateful if someone could explain the following
abbreviations - SLP and ISA :)

--
Tomasz Lewicki

[Greg Troxel]

Tomasz Lewicki <barbap...@gmail.com> writes:

> abbreviations - SLP and ISA :)

Sea Level Pressure

https://en.wikipedia.org/wiki/International_Standard_Atmosphere

[Tomasz Lewicki]

OK, so I was using these terms without knowing them :)