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Your Questions About Google Earth

August 4, 2013

Joseph asks…

What are the controls for the google earth plane on a mac book?

what are the controls for the google earth plane on a mac book? I want to know like how to do page up and down and how to turn easily

Administrator answers:

Cool. Didn’t know about this feature until googling it. Instructions below.

Jenny asks…

How long does it take for a picture to appear in Google Earth?

How long will it take for a picture to appear on Google Earth when I uploaded today through Panoramio?

Thanks!!!

Administrator answers:

It will upload whenever google gets new picturess form that section. This can take seconds to months. No way to know for sure

Steven asks…

How does Google Earth get details of ocean floors?

Not sure where this question should be posted. I am amazed at the detail of the ocean floor topography that can be seen using Google Earth. How do they do that?

Administrator answers:

They do not use “sonar” from satellites, nor do they use lasers or light images with some sort of miraculous filters that filter out the water. Light will only penetrate a few hundred feet into water and sonar is sound, which does not exist in space due to lack of a medium to transmit it. The gravity measurements made from satellites are a technique that has been used for decades using airplanes to carry the equipment. The satellite just makes a more stable platform for the technology.

Most of the data is obtained by shipboard sonar tracking and over many decades the data has been compiled into a large database by organizations such as IHO (International Hydrographic Organization) and NOAA. Current satellite technology has indeed improved and added to the database using measurements of gravity. Small changes in the earth’s gravitational force are the result of the difference in density between seafloor rock and water, so this difference can be calculated to measure the bathymetry. It can also have errors in it related to variations in rock density of the seafloor.

Here is an explanation from NOAA:
“This new estimate of seafloor topography was obtained from shipboard depth soundings combined with gravity data derived from satellite altimetry to produce a gridded representation of seafloor topography for all ice-free ocean areas within +/-72 degrees latitude. The depth data were obtained by screening 6905 surveys from the NGDC (Marine Trackline Geophysics CD-ROM version 3.2), the Scripps Institution of Oceanography and Lamont-Doherty Earth Observatory databanks, and other data, using quality control procedures based on those of Smith [J. Geophys. Res. 98, 9591-9603, 1993]. The satellite gravity field combines all data from the ERS-1 and GEOSAT satellites including the data declassified in 1995; it has an RMS accuracy of 3-5 mGal and a resolution of 20-30 km wavelength [Sandwell and Smith, J.Geophys. Res. 102, 10,039-10,054, 1997].”

http://www.ngdc.noaa.gov/mgg/fliers/97mgg03.html

Also see:

http://www.ngdc.noaa.gov/mgg/gebco/gebco.html

NOAA also maintains a GIS interface (which may be where Google gets its data) of multibean bathymetric data here:

http://map.ngdc.noaa.gov/website/mgg/multibeam/viewer.htm

also see:

http://map.ngdc.noaa.gov/website/mgg/nos_hydro/viewer.htm

That is an interactive online mapping tool that can be used to understand the amount and density of the data that is used for these seafloor topographic images. I would caution you that when using Google Earth to view this topography, you must consider that good graphics do not mean what you are seeing is accurate. In other words, you shouldn’t believe everything you see in Google Earth.

Edit: Gravity measurements are nothing like sonar. Gravity is not transmitted BY the satellite. It is merely measured by the satellite. Sonar is actively transmitted from the source (such as a ship or submarine), much as a laser would have to be transmitted and returned to its source. If you read my third paragraph carefully you will discover that satellites (and airplanes) do not use sonar, but only gravity. There is no similarity between a “system like sonar” and a gravity measurement. Ships use sonar.

Sources are added to back up my answers. This is my normal technique for answering questions. My purpose is to educate and provide verification, as well as providing sources of additional information for the asker to reference.

Sandy asks…

What time of day does the Google Earth satellite take its pictures?

I want to know what time of day and, if possible, how often the satellite for Google Earth/Google Maps takes its pictures. If anyone knows, please answer.

Administrator answers:

Most of the photos on there are between 1-3 years old. Given that, time of day is irrelevant though I would assume early afternoon to keep brightness high and shadows to a minimum.

Paul asks…

How might geography students use google earth?

just wondering- i need to think of a way in which geography students could make use of Google Earth.. something to do with GIS if possible!

Administrator answers:

Just check these link:

http://rms.rutlandcitypublicschools.org/2010/11/09/synergy-students-google-earth-explore-geography/

^_~

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