OT How does GMaps know elevation? - Page 3

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
Re: OT How does GMaps know elevation?
In alt.home.repair, on Thu, 1 Aug 2019 09:12:16 +1000, Clifford Heath

Quoted text here. Click to load it

Better be careful who you let into your house!

Re: OT How does GMaps know elevation?
On 7/31/19 11:18 PM, micky wrote:
Quoted text here. Click to load it


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?


Re: OT How does GMaps know elevation?
On 01/08/2019 00:12, Clifford Heath wrote:
Quoted text here. Click to load it

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


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

Re: OT How does GMaps know elevation?
On 08/01/2019 01:16 AM, N_Cook wrote:
Quoted text here. Click to load it

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

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




Re: OT How does GMaps know elevation?


Quoted text here. Click to load it

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


Re: OT How does GMaps know elevation?
On Tue, 30 Jul 2019 15:24:37 -0400, "\"Retired"@home.com wrote:

Quoted text here. Click to load it


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     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
We've slightly trimmed the long signature. Click to see the full one.
Re: OT How does GMaps know elevation?
On 7/30/2019 11:43 AM, micky wrote:
Quoted text here. Click to load it
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?id10%.1371/journal.pone.0175756

Apparently there are lots of accurate sources for elevation data.

Re: OT How does GMaps know elevation?
On 07/30/2019 12:43 PM, micky wrote:
Quoted text here. Click to load it

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.

Re: OT How does GMaps know elevation?
On Tuesday, July 30, 2019 at 11:43:32 AM UTC-7, micky wrote:
Quoted text here. Click to load it

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.

Re: OT How does GMaps know elevation?
Quoted text here. Click to load it

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.

Re: OT How does GMaps know elevation?
On 07/31/2019 03:06 AM, Rob wrote:
Quoted text here. Click to load it

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.

Re: OT How does GMaps know elevation?
micky wrote:

Quoted text here. Click to load it
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: snipped-for-privacy@Hovnanian.com
------------------------------------------------------------------
We've slightly trimmed the long signature. Click to see the full one.

Site Timeline