OT How does GMaps know elevation?

[micky]

When you use google maps to choose a route between two locations, and
choose walking or bicycling, it also shows starting and ending elevation
and a graph that shows changes, so you can see how many and how big the
hills are. Also useful, of course, just for finding elevation without
any walking.

But how does it know elevation. If a GPS gets signals from 3
satellites, it can calculate location, and if it gets signals from 4 of
them, it can calculate elevation. But the calculation is made in the
GPS device, such as a smartphone. Google doesn't have GPS devices at
any random location the user picks, and it has no way to read satellite
signals.

Is there some topographical map underlying the google maps, even though
there is no way to display that map wwithin google?

[Jeff Urban]

Satellite.

[N_Cook]

Check out a convenient Google height and you'll find its a load of junk.
In the UK luckily there are still a lot of surviving Ordnance Survey
benchmarks around and you can optically survey to them and easily get to
mm accurace if no more than 1-200m away (wrt the old map data containing
benchmark heights).
It is possible of course that the underlying land has risen or fallen
from post glacial isostatic rebound or water/oil extraction etc.
But even with mobile phone link dGPS (aGPS) surveying the
resolution/repeatability is no better than 15mm. And can easily be a lot
worse and without a second method (eg benchmarks) you won't know.
Outside the UK I've no idea if there are other networks of benchmarks.
I would like to find an "ap" where , as the GPS orbits are known , that
it would be possible to find times in the near future where 4 satellites
would be near enough overhead and none at lower elevation.
I wonder what sort of height determination you could get with that for
height determination.









--
Monthly public talks on science topics, Hampshire , England
<http://diverse.4mg.com/scicaf.htm>

[Andy Burns]

micky wrote:

> Google doesn't have GPS devices at
> any random location the user picks

Every user carrying a GPS enabled android device is crowd-sourcing data
for google, if someone's been there, google will know the altitude.

["\"Re...@home.com]

On 7/30/19 2:43 PM, micky wrote:
>
>
> Is there some topographical map underlying the google maps, even though
> there is no way to display that map wwithin google?

>

If you click on the GMaps Menu icon (3 line "hamburger" on top left)
there is a choice called "Terrain"

While not a true USGS topo map, you get the idea.

[Scott Lurndal]

Andy Burns <use...@andyburns.uk> writes:
> Thunderbird/60.8.0
>In-Reply-To: <ho21ke161mdv4psg1...@4ax.com>
>Content-Language: en-GB
>X-Received-Bytes: 1151
>X-Received-Body-CRC: 1553258581

Nonsense.

[Bennett]

Just a guess that Google Maps could use elevation data from Google
Earth, (or its sources), which, according to this paper from 2017, makes
GE generally accurate:
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0175756

Apparently there are lots of accurate sources for elevation data.

[micky]

In alt.home.repair, on Tue, 30 Jul 2019 20:19:06 GMT,

That's a thought.

>Nonsense.

That's a thought, too!

BTW, I tried to use google walking to see how much elevation change
there was to the top of the next hill. I had thought the top of the
hill was the big street nearby, going along a crest (although crest
sounds more like a mountain than a hill.)

I found out, if it's at all correct, that's it's about halfway between
that big street and the next one aand that my elevation is about 400
feet. Typically, google directions gives three routes, and when I
changed to one of the others, it changed my elevation to 403 feet, even
though it was the same place.

It turns out I'm about 65 feet below the top of the ridge of hills a
half mile away. I think I don't get as much breeze as I would if I
were higher up. I'm not sure because I can't be in two places at once
and I spend comparitively little time farther up the hill. I like
living next to a stream, but not getting much breeze seems to be the
other side of the coin.

Does it seem correct to you that a mere 65' valley would be enough to
lessen the breeze I get?

[micky]

In alt.home.repair, on Tue, 30 Jul 2019 15:24:37 -0400,

Wow. I saw that years ago but I guess I forgot.

And that was just what I meant, a topographical map already ;inked to to
the street map.

I guess that answers the question.


Gfretwell said:
>My guess is the Google Car that shoots all of the street view pictures
>is using GPS to link the pictures to the map and they get the
>elevation data at the same time.

That would make sense, and would be a lot easier than a lot of the
things they do.

Did you all know that besides the Google Car, there is now the Google
Man, who wears the camera a couple feet above his head, and they have
streetview pictures of some places one can only walk.

I think once I saw google pictures from a bicycle.


Thanks, all.

[rbowman]

On 07/30/2019 12:43 PM, micky wrote:
> But how does it know elevation. If a GPS gets signals from 3
> satellites, it can calculate location, and if it gets signals from 4 of
> them, it can calculate elevation. But the calculation is made in the
> GPS device, such as a smartphone. Google doesn't have GPS devices at
> any random location the user picks, and it has no way to read satellite
> signals

Probably LIDAR.

https://gisgeography.com/dem-dsm-dtm-differences/

https://gizmodo.com/google-has-its-own-fleet-of-airplanes-to-map-the-world-5916290

The gizmodo article talks about photographing for the 3D imagery but
while you're flying around might as well get the LIDAR data too.

[Jeff Liebermann]

On Tue, 30 Jul 2019 15:24:37 -0400, "\"Retired"@home.com wrote:

Yep. The basic numbers come from various elevation and terrain models
and databases. For example:
<https://www.usgs.gov/faqs/where-can-i-get-elevation-data?qt-news_science_products=7#qt-news_science_products>
<https://www.usgs.gov/core-science-systems/ngp/3dep/about-3dep-products-services>
<http://vterrain.org/Elevation/global.html>
<https://gisgeography.com/free-global-dem-data-sources/>
etc. There are ground level elevation maps, maps that include tree
and building heights for urban radio propagation studies, and maps
that include ocean bottom depths instead of ocean surface. There's
even a database of elevation databases:
<https://catalog.data.gov/dataset?tags=elevation>

For radio propagation studies, I use Radio Mobile software:
<http://www.ve2dbe.com/english1.html>
and SRTM (shuttle radar topography mission) 1 arc second (30 meter)
maps:
<https://www2.jpl.nasa.gov/srtm/>

I usually take the Radio Mobile maps, which show elevation,
<http://www.learnbydestroying.com/jeffl/coverage/VZW-water-plant/Picture11a.jpg>
and overlay them with the corresponding Google Earth map to produce
something like this cell site coverage map:
<http://www.learnbydestroying.com/jeffl/coverage/VZW-water-plant/Picture11a-google-earth.jpg>

The problem in not the lack of elevation maps, but rather an
overchoice of which one to use.


--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[whit3rd]

On Tuesday, July 30, 2019 at 11:43:32 AM UTC-7, micky wrote:
> When you use google maps to choose a route between two locations, and
> choose walking or bicycling, it also shows starting and ending elevation
> and a graph that shows changes, so you can see how many and how big the
> hills are. Also useful, of course, just for finding elevation without
> any walking.
>

> But how does it know elevation. If a GPS gets signals...

Elevation maps have been made before satellites, from aerial surveys; just the
change in position of objects with motion of a plane (flying a well-known path)
causes the successive images to show parallax. The resulting topographic
maps are widely available; orienteering wouldn't be possible without them.

[micky]

Another great discovery when clicking on the hamburger.

It has a line called streetview.

clicking that turns on all the streetview lines and dots, so that you
don't have to move Pegman each time you want to see one. You don't have
to use Pegman at all, just click on the location, and after you close
that window, the map with all streetview lines and dots will still be
there.

Did you all know that when a streetview on a line is open and there is
an arrow superimposed on the pavement, you can click on the arrow and
the next circular picture will be displayed, and maybe you can skip
ahead 2 or 3 pictures if you position the arrow farther away. This is
good when you're looking for the perfect view or something specific.


In alt.home.repair, on Tue, 30 Jul 2019 19:17:45 -0400, micky

[Rob]

micky <NONONO...@bigfoot.com> wrote:
>
>
> When you use google maps to choose a route between two locations, and
> choose walking or bicycling, it also shows starting and ending elevation
> and a graph that shows changes, so you can see how many and how big the
> hills are. Also useful, of course, just for finding elevation without
> any walking.
>
> But how does it know elevation. If a GPS gets signals from 3
> satellites, it can calculate location, and if it gets signals from 4 of
> them, it can calculate elevation. But the calculation is made in the
> GPS device, such as a smartphone. Google doesn't have GPS devices at
> any random location the user picks, and it has no way to read satellite
> signals.

Google maps is not related to GPS!
Google maps is a MAP. A static piece of data that you can navigate.

When you have a map on paper (no idea how old you are and if you
have ever seen one), you don't ask "how can the map know this road
is here when it doesn't use GPS" either.

[Rob]

Google maps doesn't feed back user information into the maps, they
use existing survey data and also do their own surveys and photography.

The only feedback you see in the maps is the traffic info, obtained
by observing speed of users along roads.

[rbowman]

On 07/31/2019 03:06 AM, Rob wrote:
> Google maps is not related to GPS!
> Google maps is a MAP. A static piece of data that you can navigate.
>
> When you have a map on paper (no idea how old you are and if you
> have ever seen one), you don't ask "how can the map know this road
> is here when it doesn't use GPS" either.

It's related so far as the rendered map is based on WGS84 and a
particular latitude and longitude relates to a number of tiles (png's)
depending on the zoom level.

Ultimately it relates to vector data that describes the road and is
rendered to produce the map tiles. The Google cars are collecting
photographic data but they are also collecting the GPS coordinates used
to build or update the vector data.

The photographic material is geotagged so it can be related to the
location. Mist smart phones and newer digital cameras do the same thing.
The EXIF data embedded in the image contains the location where the
photo was taken.

http://exifdata.com/

Note that is you run around taking selfies your camera or phone might
rat you out by putting you in a specific place at a specific time. The
same data allows you to position the photo accurately on a digital map.


Paper maps tended to do a lot of guessing.

[rbowman]

On 07/31/2019 03:08 AM, Rob wrote:
> Google maps doesn't feed back user information into the maps, they
> use existing survey data and also do their own surveys and photography.

https://support.google.com/maps/answer/3094088

Google does receive user input. OSM (Open Street Map) depends on user
input to a great extent although some information comes from publicly
available data like TIGER/Line in the US. Especially in Europe it can be
very accurate.

[Rob]

This does not list "incorrect local terrain height" and also it is a
manual process for correcting errors. There is no such thing as a
feature in Google Maps that tracks your GPS position and reports it
back to Google for inclusion in the maps. The road information comes
from offcial (and their own) surveys, it is not like a road will be added
to the map when one or more Google Maps users cross a field somewhere.

And similarly, the local terrain height is not influenced by the height
indicated by users when they use Google Maps.

[Robert Roland]

On Tue, 30 Jul 2019 19:17:45 -0400, micky <NONONO...@bigfoot.com>
wrote:

>I think once I saw google pictures from a bicycle.

They even use sheep these days:

https://visitfaroeislands.com/sheepview360/thanks-sheep-view-faroe-islands-now-google-street-view/
--
RoRo

[Clifford Heath]

On 31/7/19 9:17 am, micky wrote:
> Did you all know that besides the Google Car, there is now the Google
> Man, who wears the camera a couple feet above his head, and they have
> streetview pictures of some places one can only walk.

Including inside some malls and department stores. I forget where I saw
that.

[rbowman]

On 07/31/2019 11:30 AM, Rob wrote:
> This does not list "incorrect local terrain height" and also it is a
> manual process for correcting errors. There is no such thing as a
> feature in Google Maps that tracks your GPS position and reports it
> back to Google for inclusion in the maps. The road information comes
> from offcial (and their own) surveys, it is not like a road will be added
> to the map when one or more Google Maps users cross a field somewhere.

If the field happens to be a new development?

[micky]

In alt.home.repair, on Thu, 1 Aug 2019 09:12:16 +1000, Clifford Heath

Better be careful who you let into your house!

[micky]

In alt.home.repair, on Wed, 31 Jul 2019 21:05:01 +0200, Robert Roland

Wow. That's good. They go slowly so the pictures won't be blurred.

[micky]

In alt.home.repair, on 31 Jul 2019 17:30:36 GMT, Rob

<nom...@example.com> wrote:

>
>This does not list "incorrect local terrain height" and also it is a
>manual process for correcting errors. There is no such thing as a
>feature in Google Maps that tracks your GPS position and reports it
>back to Google for inclusion in the maps. The road information comes
>from offcial (and their own) surveys, it is not like a road will be added
>to the map when one or more Google Maps users cross a field somewhere.
>
>And similarly, the local terrain height is not influenced by the height
>indicated by users when they use Google Maps.

How does GMaps get updates to street maps.

Does it infer the streets from computer analysing the sat view?

Or do municiplities send it updates when they construct new streets?

In some places, they show paths between houses with a dotted line? Who
tells GMaps about the paths? If you choose Walking, it will route you
over the path, but no other method of travel will go that way.

[N_Cook]

Part of the Kennet and Avon Canal towpath in England is on "strretview"
, no street anywhere near

[leftaphobic]

We all know google leans left so why would you be afraid to have a democrat from google inventory your house?
Isn't socialism all about sharing?

[rbowman]

On 08/01/2019 01:16 AM, N_Cook wrote:
> On 01/08/2019 00:12, Clifford Heath wrote:
>> On 31/7/19 9:17 am, micky wrote:
>>> Did you all know that besides the Google Car, there is now the Google
>>> Man, who wears the camera a couple feet above his head, and they have
>>> streetview pictures of some places one can only walk.
>>
>> Including inside some malls and department stores. I forget where I saw
>> that.
>>
>
> Part of the Kennet and Avon Canal towpath in England is on "strretview"
> , no street anywhere near
>
>

https://mashable.com/2017/04/27/google-street-trekker-sg/

https://gizmodo.com/you-can-apply-to-use-googles-street-view-backpack-now-631925651

[Rob]

micky <NONONO...@bigfoot.com> wrote:
> In alt.home.repair, on 31 Jul 2019 17:30:36 GMT, Rob
> <nom...@example.com> wrote:
>
>>
>>This does not list "incorrect local terrain height" and also it is a
>>manual process for correcting errors. There is no such thing as a
>>feature in Google Maps that tracks your GPS position and reports it
>>back to Google for inclusion in the maps. The road information comes
>>from offcial (and their own) surveys, it is not like a road will be added
>>to the map when one or more Google Maps users cross a field somewhere.
>>
>>And similarly, the local terrain height is not influenced by the height
>>indicated by users when they use Google Maps.
>
> How does GMaps get updates to street maps.
>
> Does it infer the streets from computer analysing the sat view?
>
> Or do municiplities send it updates when they construct new streets?

The latter.
In regions with new streets or buildings you can see streets on the
streetview and bare land in the sat view.

[Rob]

Streets are shown in new developments even when they not yet have been
laid, but have been submitted as planned.

[Rod Speed]

"micky" <NONONO...@bigfoot.com> wrote in message
news:ahm4kelg4g9if9l7h...@4ax.com...

They go pretty fast when the Faroe Islanders are trying to fuck them.

[peterw...@gmail.com]

That would be Utah!

Where the men are men, and the sheep are all nervous.

Peter Wieck
Melrose Park, PA

[Rod Speed]

"micky" <NONONO...@bigfoot.com> wrote in message

news:lrm4ke5jcbe9nlj1a...@4ax.com...

> In alt.home.repair, on 31 Jul 2019 17:30:36 GMT, Rob
> <nom...@example.com> wrote:
>
>>
>>This does not list "incorrect local terrain height" and also it is a
>>manual process for correcting errors. There is no such thing as a
>>feature in Google Maps that tracks your GPS position and reports it
>>back to Google for inclusion in the maps. The road information comes
>>from offcial (and their own) surveys, it is not like a road will be added
>>to the map when one or more Google Maps users cross a field somewhere.
>>
>>And similarly, the local terrain height is not influenced by the height
>>indicated by users when they use Google Maps.

> How does GMaps get updates to street maps.

Here they get it from the operation that is doing the new streets.

> Does it infer the streets from computer analysing the sat view?

That wouldn't give them the street names.

> Or do municiplities send it updates when they construct new streets?

Not send google so much as update their database and google accesses those.
We have seen it take a while before the google map is updated with new ones.
This is one example.
https://www.google.com/maps/@-34.2703494,146.0873386,16.33z
Tucker and Gillmartin are now well past Haines with new houses being
built on the new bits of Tucker and Gillmartin now.

> In some places, they show paths between houses with a dotted line?
> Who tells GMaps about the paths?

With ours they are on the council maps, what you call municipalitys.

> If you choose Walking, it will route you over the path,
> but no other method of travel will go that way.

Ours work fine for bicycles but google doesn't use them for bikes.

[Rod Speed]

"N_Cook" <div...@tcp.co.uk> wrote in message
news:qhu3jf$uve$1...@dont-email.me...

> On 01/08/2019 00:12, Clifford Heath wrote:
>> On 31/7/19 9:17 am, micky wrote:
>>> Did you all know that besides the Google Car, there is now the Google
>>> Man, who wears the camera a couple feet above his head, and they have
>>> streetview pictures of some places one can only walk.
>>
>> Including inside some malls and department stores. I forget where I saw
>> that.
>>
>
> Part of the Kennet and Avon Canal towpath in England is on "strretview" ,
> no street anywhere near

Can you post a proper link ? I can only get google maps to show photos of
it.

[Peeler]

On Fri, 2 Aug 2019 04:30:52 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

<FLUSH senile asshole's latest trollshit>

04:30 am??? Whatsa matter, senile Rodent? Did you "sleep in" today? ROTFLOL

--
Richard addressing Rot Speed:
"Shit you're thick/pathetic excuse for a troll."
MID: <ogoa38$pul$1...@news.mixmin.net>

[Peeler]

On Fri, 2 Aug 2019 04:54:14 +1000, cantankerous trolling geezer Rodent

Speed, the auto-contradicting senile sociopath, blabbered, again:

>> How does GMaps get updates to street maps.
>
> Here they get it from the operation that is doing the new streets.

Yeah, but HE is not "here", senile Ozzietard!

--
The Natural Philosopher about senile Rot:
"Rod speed is not a Brexiteer. He is an Australian troll and arsehole."
Message-ID: <pu07vj$s5$2...@dont-email.me>

[Peeler]

On Fri, 2 Aug 2019 05:00:33 +1000, cantankerous trolling geezer Rodent

Speed, the auto-contradicting senile sociopath, blabbered, again:

>> Part of the Kennet and Avon Canal towpath in England is on "strretview" ,
>> no street anywhere near
>
> Can you post a proper link ? I can only get google maps to show photos of
> it.

Hey, senile useless troll, wouldn't THAT be the perfect job for you, you
ridiculous Google, M$ and Apple adorer: run around with a stupid Google
camera a few feet above your senile head and send the data to your beloved
Google? LOL

--
dennis@home to retarded senile Rot:
"sod off rod you don't have a clue about anything."
Message-ID: <uV9lE.196195$cx5....@fx46.iad>

[Paul Hovnanian P.E.]

micky wrote:

> Is there some topographical map underlying the google maps,

Several. USGS probably releases topographical data. There is also data from
the Shuttle Radar Topography Mission (SRTM). See:
https://www2.jpl.nasa.gov/srtm/

Several projects attached to the Open Street Map project inculde tools to
integrate SRTM data into maps installable on various GPS devices.

--
Paul Hovnanian mailto:Pa...@Hovnanian.com
------------------------------------------------------------------
Write a wise saying and your name will live forever. -- Anonymous

[Rob]

Rod Speed <rod.sp...@gmail.com> wrote:
>> Or do municiplities send it updates when they construct new streets?
>
> Not send google so much as update their database and google accesses those.
> We have seen it take a while before the google map is updated with new ones.

I guess it depends on the quality of your local database.
Here we see new streets and quarters on Google Maps that do not yet
exist in reality (but have been planned and will be built).

[Rod Speed]

"Rob" <nom...@example.com> wrote in message
news:slrnqkd7o9...@xs9.xs4all.nl...

> Rod Speed <rod.sp...@gmail.com> wrote:
>>> Or do municiplities send it updates when they construct new streets?
>>
>> Not send google so much as update their database and google accesses
>> those.
>> We have seen it take a while before the google map is updated with new
>> ones.
>
> I guess it depends on the quality of your local database.

The local database is fine, it just takes google a long time to use the
updates.

> Here we see new streets and quarters on Google Maps that do
> not yet exist in reality (but have been planned and will be built).

That not necessarily due to the quality of the local database.

We saw the google car show up again here almost 18 months
ago, after it had been here previously more than 10 years
previously. The second time they only zoomed thru some
of the main streets in town and didn’t even bother to
visit the new roads and houses.

[Peeler]

On Sun, 4 Aug 2019 19:51:01 +1000, cantankerous trolling geezer Rodent

Speed, the auto-contradicting senile sociopath, blabbered, again:

<FLUSH the auto-contradicting senile asshole's latest trollshit>

--
Website (from 2007) dedicated to the 85-year-old trolling senile
cretin from Oz:
https://www.pcreview.co.uk/threads/rod-speed-faq.2973853/

[rbowman]

I do a lot of work with local GIS departments and the quality is
extremely variable. Some are on top of it and others are completely out
of their depth. At least one uploads their edits to ESRI and not Google.
Google puts their dispatch center in the wrong place so they don't
exactly trust them.


There are several big players like HERE (formerly NavTeq) and TeleAtlas.
Licensing their data isn't cheap and depends on how frequently you want
it updated. TIGER/Line is the US Census Department and the data is free
but the update cycle is slow. It's interesting to take the data for the
same area from several different sources, overlay it, and see where it
differs.

[Rob]

Rod Speed <rod.sp...@gmail.com> wrote:
>
>
> "Rob" <nom...@example.com> wrote in message
> news:slrnqkd7o9...@xs9.xs4all.nl...
>> Rod Speed <rod.sp...@gmail.com> wrote:
>>>> Or do municiplities send it updates when they construct new streets?
>>>
>>> Not send google so much as update their database and google accesses
>>> those.
>>> We have seen it take a while before the google map is updated with new
>>> ones.
>>
>> I guess it depends on the quality of your local database.
>
> The local database is fine, it just takes google a long time to use the
> updates.

It likely is all coincidence. They fetch the info once every so
many years, and it could include very recent information or it could
take several years.

>> Here we see new streets and quarters on Google Maps that do
>> not yet exist in reality (but have been planned and will be built).
>
> That not necessarily due to the quality of the local database.
>
> We saw the google car show up again here almost 18 months
> ago, after it had been here previously more than 10 years
> previously. The second time they only zoomed thru some
> of the main streets in town and didn’t even bother to
> visit the new roads and houses.

This is not at all related to it. The google car does not map the
streets, it collects data and pictures.

[Rod Speed]

"Rob" <nom...@example.com> wrote in message

news:slrnqkegpk...@xs9.xs4all.nl...

> Rod Speed <rod.sp...@gmail.com> wrote:
>>
>>
>> "Rob" <nom...@example.com> wrote in message
>> news:slrnqkd7o9...@xs9.xs4all.nl...
>>> Rod Speed <rod.sp...@gmail.com> wrote:
>>>>> Or do municiplities send it updates when they construct new streets?
>>>>
>>>> Not send google so much as update their database and google accesses
>>>> those.
>>>> We have seen it take a while before the google map is updated with new
>>>> ones.
>>>
>>> I guess it depends on the quality of your local database.
>>
>> The local database is fine, it just takes google a long time to use the
>> updates.
>
> It likely is all coincidence. They fetch
> the info once every so many years,

Why would they do it so slowly ?

And the google maps don’t show the new ones in bursts like that.

> and it could include very recent information or it could take several
> years.
>
>>> Here we see new streets and quarters on Google Maps that do
>>> not yet exist in reality (but have been planned and will be built).
>>
>> That not necessarily due to the quality of the local database.
>>
>> We saw the google car show up again here almost 18 months
>> ago, after it had been here previously more than 10 years
>> previously. The second time they only zoomed thru some
>> of the main streets in town and didn’t even bother to
>> visit the new roads and houses.

> This is not at all related to it. The google car does not map the
> streets, it collects data and pictures.

Duh.

[Peeler]

On Mon, 5 Aug 2019 07:36:29 +1000, cantankerous trolling geezer Rodent

Speed, the auto-contradicting senile sociopath, blabbered, again:

> Duh.

Yep, those three letters sum up your entire existence, senile cretin!

--
Sqwertz to Rot Speed:
"This is just a hunch, but I'm betting you're kinda an argumentative
asshole.
MID: <ev1p6ml7ywd5$.d...@sqwertz.com>

[Mike S]

On 7/30/2019 1:19 PM, Scott Lurndal wrote:
> Andy Burns <use...@andyburns.uk> writes:
>> Thunderbird/60.8.0
>> In-Reply-To: <ho21ke161mdv4psg1...@4ax.com>
>> Content-Language: en-GB
>> X-Received-Bytes: 1151
>> X-Received-Body-CRC: 1553258581
>>
>> micky wrote:
>>
>>> Google doesn't have GPS devices at
>>> any random location the user picks
>>
>> Every user carrying a GPS enabled android device is crowd-sourcing data
>> for google, if someone's been there, google will know the altitude.
>
> Nonsense.

How so? Wikipedia says this:

"Global Positioning System (GPS) receivers can also determine altitude
by trilateration with four or more satellites. In aircraft, altitude
determined using autonomous GPS is not reliable enough to supersede the
pressure altimeter without using some method of augmentation"

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

[rbowman]

Barometric altimeters aren't that great either. I haven't flown in years
so the procedure might have changed but airports would have their
elevation prominently marked. Part of the preflight was setting the
altimeter to match.

[Swer]

"rbowman" <bow...@montana.com> wrote in message
news:gqtgob...@mid.individual.net...

That’s because air pressure changes. Laser height measuring from
satellites and planes for mapping works fine and is a lot more
accurate than GPS.

[Peeler]

On Wed, 7 Aug 2019 03:28:15 +1000, Sewer, better known as cantankerous
trolling senile geezer Rodent Speed, wrote:

> That’s because air pressure changes. Laser height measuring from
> satellites and planes for mapping works fine and is a lot more
> accurate than GPS.

"GPS"? Does that stand for "Geriatric Pile of Shit" in your case, senile
Rodent?

--
MrTu...@down.the.farm about senile Rot Speed:
"This is like having a conversation with someone with brain damage."
MID: <ps10v9$uo2$1...@gioia.aioe.org>

[et...@whidbey.com]

Why is laser measuring much more accurate than GPS? They both use
light and clocks.
Eric

[Scott Lurndal]

GPS doesn't use lasers. The receiver triangulates signals from multiple
satellites to determine x, y and z coordinates of the receiver.

The z coordinate (altitude) is not very accurate

http://gpsinformation.net/main/altitude.htm

[et...@whidbey.com]

On Tue, 06 Aug 2019 19:30:56 GMT, sc...@slp53.sl.home (Scott Lurndal)
wrote:

I know GPS doesn't use lasers. It uses radio waves which are light and
move the same speed as lasers. What is it about using lasers that
makes them more accurate?
Eric

[Swer]

<et...@whidbey.com> wrote in message
news:k8ljkedtv1dhiibk1...@4ax.com...

Because the laser is the most accurate way to measure things.

> They both use light

GPS doesn't. It used radio waves.

> and clocks.

Yes.

[Swer]

<et...@whidbey.com> wrote in message
news:1fvjkedv5a8q9b7j8...@4ax.com...

It's a direct ping from the satellite or plane with the laser.
With GPS its continuous radio waves with varying propagation
effects. That's why you need more than one visible satellite
with GPS.

[rbowman]

A GPS receiver extrapolates from the satellite constellation. The closer
to the horizon the birds are and the more angular distance separating
them, the better it works. In cities or mountainous terrain the view of
the sky can be limited so it has to work with those overhead. It has
nothing to do with light unless you have an extremely loose definition
of the spectrum.

With a laser you're bouncing the beam off an object.

[Peeler]

On Wed, 7 Aug 2019 09:51:56 +1000, Sewer, better known as cantankerous

trolling senile geezer Rodent Speed, wrote:

>> I know GPS doesn't use lasers. It uses radio waves which are light and
>> move the same speed as lasers. What is it about using lasers that
>> makes them more accurate?
>
> It's a direct ping from the satellite or plane with the laser.
> With GPS its continuous radio waves with varying propagation
> effects. That's why you need more than one visible satellite
> with GPS.

SOURCE, senile Mr Know-it-all? I KNOW you just looked it up, just so you
could smartass again, you pathological, lonely, senile sow!

[Peeler]

On Wed, 7 Aug 2019 09:38:11 +1000, Sewer, better known as cantankerous

trolling senile geezer Rodent Speed, wrote:


>

>> Why is laser measuring much more accurate than GPS?
>
> Because the laser is the most accurate way to measure things.

Dig this, senile troll from Oz: a troll's posts are the most accurate way to
measure the extent of his trolling. They knew that already back then in 2007
when the dedicated that website to you:

https://www.pcreview.co.uk/threads/rod-speed-faq.2973853/

[Mike Coon]

In article <1fvjkedv5a8q9b7j8...@4ax.com>,
et...@whidbey.com says...

>
> I know GPS doesn't use lasers. It uses radio waves which are light and
> move the same speed as lasers. What is it about using lasers that
> makes them more accurate?
> Eric

Wavelength.

Mike.

[Mike Coon]

In article <gquhba...@mid.individual.net>, sw...@gmail.com says...

>
> > Why is laser measuring much more accurate than GPS?
>
> Because the laser is the most accurate way to measure things.

Did your mummy say "Because I said so!" a lot?

Mike.

[Rod Speed]

"Mike Coon" <gra...@mjcoon.plus.com> wrote in message
news:MPG.37b5290...@news.plus.net...

Nope, it's a laser pulse from the plane or satellite, travel time measured.

GPS is continuous transmission with digital encoding on that.

[Swer]

Mike Coon <gra...@mjcoon.plus.com> wrote
> sw...@gmail.com wrote

>>> Why is laser measuring much more accurate than GPS?

>> Because the laser is the most accurate way to measure things.

> Did your mummy say "Because I said so!" a lot?

Nope, both mum and dad quickly worked out that doesn't work with me.

I still remember the mega stoush that happened when I refused
to eat something like spinach. She never tried that again.

[Peeler]

On Thu, 8 Aug 2019 05:16:51 +1000, cantankerous trolling geezer Rodent

Speed, the auto-contradicting senile sociopath, blabbered, again:

>> Wavelength.
>
> Nope

LOL

--
Kerr-Mudd,John addressing senile Rot:
"Auto-contradictor Rod is back! (in the KF)"
MID: <XnsA97071CF43...@85.214.115.223>

[Peeler]

On Thu, 8 Aug 2019 05:19:22 +1000, Sewer, better known as cantankerous

trolling senile geezer Rodent Speed, wrote:

> Nope, both mum and dad quickly worked out that doesn't work with me.
>
> I still remember the mega stoush that happened when I refused
> to eat something like spinach. She never tried that again.

For once I believe, little psychopath!