How often are the Google Maps satellite images updated?

Q. We've done quite a bit of renovations on our little farm and I'm curious when we'll get to see a change in the satellite view on Google Maps or Google Earth.

A. Google purchases the images from many different sources. Most of the images are purchased second hand - basically the images are not taken for the sole purpose of supplying them to Google. Most of the images are taken for completely different reasons and released to the public or sold to Google for extra profit.

Suggestion - your local government agency (county or city) should have a Geographic Information Sytems (GIS) department or division. They could be a great source of aerial photography.

I work for my local GIS division and we have images at 6" resolution taken in spring of 2008, 2007, 2006, 2003, 2001, and 1997.

Check with your local government - they will be the best source for updated imagery.

Why do deserts look dark and streaky in satellite images?

Q. just looked at the Sahara desert on google maps satellite image and the image looks as though someone has gone over it with a rake- lots of fine stripes heading east west and larger areas of colour giving the feeling of motion in an east-westerly direction. So what is this? Dunes? Sandstorms? But they cover the entire desert! And why do many of the streaks look so dark, almost black? I then looked at the Arabian desert- same thing. Then looked at Australian desert and it didn't seem to have this streaky pattern at all. So what is this?

A. I think it might be because of the direction in which the wind has blown the sand across the plains. the wind will also create Dunes which will create a change in direction of the streaks or a change in thickness.
They look dark due to the shadows created by the raised and less raised streaks of sand which have built up.

I Hope this helps somehow. :S

What do the numbers mean on top of buildings in downtown Los Angeles?

Q. When I look at downtown L.A. on the Google Maps satellite view, I see *a lot* of rooftops that have a number in a circle on them. The number is usually 10 but occasionally is 8 or 12. I've wondered if these are heliports, but it seems odd that there would be so many of them.

I thought that the numbers might simply be notations of some kind added by Google, but I don't see them on rooftops in other cities.

What do the numbers mean?

A. The circled numbers are on rooftop helipads. They define the weight limit of the pad.

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