Rara From Germany, joined Jan 2007, 2112 posts, RR: 2
Reply 6, posted (2 years 3 months 4 weeks 9 hours ago) and read 1752 times:
In fact there are quite some misconceptions about how satellite imagery works, mainly due to spy movies and suchlike.
In order for a satellite to photograph something even remotely to Google Earth quality standards, it needs to be in low earth orbit. Low earth orbit means that the satellite moves tenths of kilometers every *second*, so you'll only get a still photo of what you're interested in, it'll be low quality, and even if you're military you can only get the next update 15 minutes or so later. Live pictures of moving vehicles, like you'd see in a movie, are impossible. Any photograph you get is a lucky shot.
Of course satellites can be in geostationary orbit, but that has to be a lot further out (as in like a 100 times further out) from which they could theoretically keep observing the same spot, but from that distance you can't get any meaningful pictures (except of a huge area, of a whole weather system maybe).
In other words, Live Google Earth is impossible.
Quoting zkojq (Reply 5): 2) Most urban areas in google earth/maps are actually done by aerial photography, not satellite imagery.
Correct - aerial photography is much better for their purpose..
Samson was a biblical tough guy, but his dad Samsonite was even more of a hard case.
I would say it depends on the areas. Popular areas would be updated more frequently. The more interesting and frequented areas on Google Earth are low altitude images, so I would guess the satellite pictures used for higher levels aren't updated that frequently as things don't change that much at that resolution anyway.
Lower altitude images would be updated more frequently, but aerial surveys are expensive so, again, it would depend on the viewing traffic in a particular area.
Many areas (desertic, remote, rural) are still only satellite.
I wonder if they manage to get different resolutions depending on the satellite image providers, and if lower resolution = cheaper images?
Looks like I picked the wrong week to quit posting...
mandala499 From Indonesia, joined Aug 2001, 6921 posts, RR: 76
Reply 13, posted (2 years 3 months 3 weeks 6 days 1 hour ago) and read 1471 times:
Quoting francoflier (Reply 11): I wonder if they manage to get different resolutions depending on the satellite image providers, and if lower resolution = cheaper images?
Yes... general rule of thumb... the higher the complexity, the more expensive it is. Complexity can come in terms of spectral complexity, or resolution. Highly complex spectral imagery at high resolution = very expensive... the image resolution gets translated into the available mapscales.
For live satellite imagery, well, they're very expensive... and these satellites move as they're in low earth orbit (high detailed ones, and cross out geostationary satellite imagery out of our fantasy list at the moment).. so any spot you want to monitor, the satellite needs to position itself onto an ideal orbit which gives it maximum exposure time to view the spot with its camera... ain't cheap... those spy satellites are not called "orbital gas tanks" for no reasons.
Some make these services available to "qualified customers"... but, can't divulge much...
When losing situational awareness, pray Cumulus Granitus isn't nearby !