Comments on: GE users vs NWW users

By: kyle brown

kyle brown — Tue, 30 Oct 2007 18:06:36 +0000

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By: reza1962wordpresscom

reza1962wordpresscom — Sat, 22 Sep 2007 09:51:02 +0000

I am want to use free Google earth to give me sun mapps in south iraq now thank you very mauch

By: Goofing Around With Pan-sharpening - Free Geography Tools

Goofing Around With Pan-sharpening - Free Geography Tools — Thu, 20 Sep 2007 14:37:57 +0000

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By: what_nick

what_nick — Thu, 20 Sep 2007 00:01:13 +0000

As I noted panchromatic imagery is very useful and I process a lot of it. http://whatnick.blogspot.com/2007/09/worldview-1-launch-and-what-to-do-with.html
The problems raised about fusion are genuine, but will be ameliorated if the satellites match orbit and for purpose imagery is taken with same off nadir angles and sun angles etc.Quickbird and WorldView both having the same operator makes such acquisition feasible.

By: Anonymous

Anonymous — Wed, 19 Sep 2007 20:11:03 +0000

Merging with different dates also brings havoc when the look angles are different, and most of the new high-res sensors can look all around causing terrible parallax problems – especially for merges. Imagine a merge of the Washington monument with a pan image captured at 20 degrees and an XS image captured at -20 degrees. Not pretty.

All that being said, B&W imagery is fine for so many applications out there – not the ‘pretty picture’ applications, but useful GIS apps.

Plus, images have to be ortho-co-registered *really* well for merging to work.

I’d be surprised if these types of merges are seen by the public very much.

By: Leszek Pawlowicz

Leszek Pawlowicz — Wed, 19 Sep 2007 20:05:55 +0000

I disagree. If you have the data out of time synch, you’ll create features that don’t reflect reality: phantom and miscolored cars and buildings, fields of snow in winter panchromatic images colored green by summer multispectral images, etc..

Moot point anyway, as the reference you quote says that this imagery isn’t intended for Google Earth, but exclusively for the National Geospatial-Intelligence Agency. Upcoming satellites for commercial purposes will have multispectral sensors in addition to the panchromatic.

By: bullsworld2007

bullsworld2007 — Wed, 19 Sep 2007 19:44:14 +0000

Yeah pan sharpening is not perfect for all occasions, for GE it should be fine though as most stuff is static, cars/tanks/people arent that important to google.

By: Leszek Pawlowicz

Leszek Pawlowicz — Wed, 19 Sep 2007 19:31:05 +0000

Yes, I’m fully aware that panchromatic imagery is higher-resolution than color – my comment references and quotes the sensor specs for the previous Quickbird satellite, which shows the panchromatic resolution at 0.6m, and the multispectral at 2.4m.

And yes, you can do pan-sharpening by combining higher-res black-and-white imagery with lower-res color imagery. But if the two datasets aren’t taken at the same time, then a pan-sharpened image may not be accurate. If there’s a major change in the imagery between the time you take the lower-res color image and the higher-res panchromatic (flood, fire, earthquake, new buildings, seasonal changes, etc.), pan-sharpening may not be valid. That’s why I speculated (incorrectly as it turns out) that the multispectral sensor specs had been left off, since not having them reduces the utility of the satellite. Especially so if you want to use the individual bands of the multispectral output to analyze information like vegetation cover (NDVI) or fire (NBR); can’t do that with panchromatic alone.