Michael Kosowsky, of HeyWhatsThat.com — a site that generates horizons for specific locations from DEM data — has emailed friends of the site to announce compatibility with Google Sky.

This is the first Earth-Sky mashup I’ve come across, and it’s a tour de force. I’ll let Michael explain: (slightly edited)

Executive Summary:

• At http://www.heywhatsthat.com generate a new panorama or view an existing one.
• Hit the new “at night” button just below the “View in Google Earth by day” button.
• Google Earth opens, switches to sky mode, and overlays the celestial sphere with the horizon, visible summits and an azimuth-altitude grid for that location at the current time.

Details:
Google Sky isn’t as good as other astronomy applications at some tasks. For example, there’s no way to indicate what portion of the sky is visible from a given location at a given time. But because Google Earth is extensible, third parties can provide functionality. And since HeyWhatsThat.com specializes in drawing your horizon…

So now when you’re looking at a panorama on HeyWhatsThat, you’ll find that instead of a “View on Google Earth” button there are two buttons: “View in Google Earth by day” and “at night”. Hit “at night” and Google Earth will open up and overlay the celestial sphere with your computed horizon and peaks and an azimuth-altitude grid reflecting the state of the sky at that instant.

You may find you have to manually switch to sky view, and if you don’t see the overlays — blue horizon line, red summit markers, and green grid lines — you’ll have to refresh the network link you just loaded: look in Google Earth for an entry on the left under Temporary Places labeled something like “Planisphere for XXXX (current),” right-click on it, and select “refresh.” And note that you can refresh it any time and the horizon will be adjusted to the current time.

(Advanced question: should I just send down the KML file rather than a NetworkLink when you click “at night”? A link that you can refresh at any time to update to current conditions is real nice, but in my testing GE hasn’t been completely reliable about refreshing the Network Link when it first receives it, forcing the complexity of the previous paragraph.)

Unfortunately, it’s been cloudy every night since the Google Sky announcement, so I haven’t been able to field test this code, but it does nicely match my childhood planisphere. In particular, I don’t currently correct for astronomical refraction, which should depress the apparent horizon by half a minute of arc; maybe tonight I’ll get to see if that would be useful.

More:
You can do more by crafting custom URLs, including computing the horizon for any specified time and for any arbitrary latitude and longitude, even locations above 60 degrees north and below 54 degrees south where we don’t have elevation data. For example,

http://www.heywhatsthat.com/bin/planisphere.cgi?lat=44.2&lon=-69.1

refers to that latitude and longitude at the current time, and

http://www.heywhatsthat.com/bin/planisphere.cgi?id=9UK4EFG7&date=8/23/2007+10:20pm+EDT

refers to the computed panorama for Bald Mountain at 10:20pm EDT on August 23. Browse to either of those links and you’ll receive the corresponding KML file; create a network link using them and you’ll be able to refresh the link at any time. See the technical FAQ for details.

If you use a URL for a fixed latitude/longitude (e.g. the first example above), the computation assumes a flat horizon, rather than trying to compute the true horizon by finding all the mountains. Arguably this is adequate for most applications — one seasoned amateur astronomer pointed out that your horizon can be off by as much as five degrees and you won’t care, because most of the time you’re looking higher in the sky — but then you can’t answer questions like “Hey, what’s that right above Bald Mountain?”

Just one note: Using a Mac with Firefox returned files with “.cgi” as the suffix, and these did not load in Google Earth. I manually changed the suffix to “.kml”, after which they loaded just fine. Fixed.

I’m so glad this blog is writing itself this week:-)

It’s a little hectic here but that shouldn’t keep me from forwarding great new examples of KML 2.2 in action. Writes EarthNC‘s Virgil Zetterlind:

I’ve published a sort of fun YouTube Airport Videos KML here. It uses the embedded video support of v4.2 in windows, but also provides the video links for Linux/Mac users. Besides the video support, I’m using the new KML 2.2 KML linking options to support navigation between videos of the same airport without ‘spamming’ placemark icons.

The file was created by running a ICAO airport identifier search against the YouTube API. As such, it’s subject to errors and it misses a large number of videos due to poor tagging. Here’s hoping that over time more people will use the geotagging options on upload and that Google will better expose geotagged results via the YouTube API.

Valery Hronusov has been playing with Google Earth 4.2 beta’s implementation of KML 2.2, and has come up with a couple of things worth sharing:

Flash: On Windows machines (but not Mac and Linux), you can embed a whole Flash applet in a placemark popup balloon (not just YouTube videos), and it will work just as if it were in a browser.

Webcams: This works on Mac, PC and Linux versions of 4.2, so it is immediately useful: Have a <PhotoOverlay> point to an image generated by a webcam, and set the <refreshInterval> tag to the same interval as the webcam’s interval. Voila, a webcam image that is perfectly positioned:

(Notice how the small thumbnail image refreshes as well.) Here’s the specific snippet of code that Valery used to get a one-second interval refresh rate:

<Icon>

     <href>http://www.url.to.image.jpg</href>

     <refreshMode>onInterval</refreshMode>

     <refreshInterval>1</refreshInterval>

</Icon>

This is definitely the way forward for georeferenced webcam images. (Remember that if you want to check out the KML code for yourself, just select a placemark, choose the Copy menu item and then Paste into a text editor. You’ll get the KML code.)

While playing with Valery’s placemark I found something this blog has overlooked until now:

Built-in PhotoOverlay controls! It turns out that rolling your own PhotoOverlay is not nearly as difficult as I had assumed. There is no need for a highly sophisticated robotic camera positioning system to record the heading, tilt and roll of a shot (though I still want the future camera that will record such data automatically as EXIF:-) — instead, just use the new Add > Photo menu item:

You then get a wonderful control panel for editing every conceivable parameter of the photo you want position:

I used the normal camera controls to get into a rough position, and then used the fine-tuning controls on the panel, which are very sensitive indeed. Especially nice is the ability to unlock the aspect ratio for the field of view. In my case, the end result proved quite respectable, for a quick effort:

While I am sure you are by now completely sick of my Alpine trek pictures, such landscape photos are practically crying out for the PhotoOverlay treatment. Luckily, I am going to be very busy this coming week so I doubt I’ll be able to subject you to any more PhotoOverlay-enhanced holiday snaps for the foreseeable future:-)

All this does imply the question: Might there not be a way to go and update Panoramio photos with an enhanced PhotoOverlaid version soon? If everyone takes responsibility for their own shots then we’ll be done in no time:-)

This made my day. Adam Franco writes:

Reading your post recapping your usage of Flickr photos in Google Earth/Maps reminded me of a small bit of code I had written a rough version of last year, but had never gotten around to cleaning up: a Flickr API script that converts all of the geotagged photos in a Flickr photo set into a KML file with a few options.

I’ve posted more details about the script on my blog and thought that you (and your readers) might be interested.

This is exactly what I’ve been wishing for, and it works wonderfully. You can choose the size of the photos in the popups, and you can even draw a path between the photo locations, based on the date taken, date uploaded or the order of the set. Using my set of georeferenced pics from the Alps, then:

View Larger Map (or get KML)

Adam’s PHP script lets you download the KML file directly or else open it in a Google Map. I did the latter, and then embedded the map to get the above result. On the larger map there is always a link to the KML file.

Adam has made the PHP script available under GNU General Public License (GPL), so you can download it here and run it off your own server if you want.

• No embedded video for Mac, Linux for now: The KML 2.2 reference documentation notes that “In Google Earth 4.2, video is supported” and goes on to show sample code for embedding YouTube video in a placemark. Unfortunately, word from informed people is that only the Windows version of Google Earth comes with the requisite embedded Flash player. “Mac & Linux do not have this, and won’t for some time.” This definitely dampens the incentive to go make KML with video content in it, as it would break the cross-platform compatibility that Google Earth 4.1 enjoyed with KML 2.1.
• 2D floorplans to 3D KML: Metropix has a novel idea that I would never have thought of. Writes Metropix’s Max Christian:
  

  GE has been used for real estate since back in 2005 of course, but the new aspect is that we have developed technology to generate furnished 3D models in GE automatically from 2D floor plans. We produce thousands of floor plans per day for real estate agents, so this will lead to quite a lot of 3D models quite quickly! There’s more information here.

  Amazon Web Services Blog also writes them up today as another fine use of their S3 scalable server service. The result is impressively detailed KML (though I can’t vouch for its accuracy) :
  

• Spreading risk spatially: Allianz Global Corporate & Specialty Insurance of Munich makes sure to spread the risk. Literally. Using Google Earth. Here’s how they do it. (Via Econdev20.com)
• Morocco’s censorship of Google Earth continues: More than a year later, Google Earth is still censored in Morocco. Francophone Motic blog has an in-depth round-up of local reactions, but concludes, depressingly, that “The censorship of Google Earth in Morocco has lasted for over a year because the majority have chosen to accept it rather than to denounce it.”

  Given that the Google Maps API provides the same data (albeit in 2D) and given that any URL can now embed a Google Map, surely somebody can point out to the Moroccan government that they’d need to close down the internet if the intent is to prevent this imagery from ever being seen by Moroccan residents.

• Multitouch demo: More Jeff Han multitouch display pr0n, on YouTube, featuring some good geospatial candy. (Thanks giasen!)

Here’s why Google Sky is going to change astronomy as we know it: Because an astronomer like Alasdair Allan can spend an afternoon converting an astronomical events feed into KML, and suddenly millions of Google Earth clients can spatially visualize these.

His events feed project, VOEvent, has its home page here, whence you can now get a live KML network link for Google Sky.

Alasdair, writing on his blog The Daily Ack, also points us in the direction of Caltech’s VOEventNet project page which collects real-time feeds of astronomical events (such as his own) of gravitational microlensing, gamma-ray bursts and x-ray bursts — as of today, all these events are also available as KML network links. For example:

Suddenly, the sky has turned into a huge canvas, ready to be updated in real time via KML.

(Alasdair has more insights in this comment to the previous post on Ogle Earth.)

News specifically about Google Earth version 4.2:

• Bad Sky? Bad Astronomy, the alpha male of astronomy blogs, gives the Sky functionality in Google Earth a mediocre review. That’s because there are several other sky viewing applications out there today that do a better job than Google Earth currently in rendering the sky (check out Stellarium, the web-based sky-map.org and the fly-through Celestia.)

  Where Google Earth/Sky shines, on the other hand, is in the annotatability of the presented data, and in the ability to let you overlay your own data via KML. Back in the early days of Google Earth, the GIS-industrial complex took a long time to understand that Google Earth prioritizes easy content creation and sharing, and that this is its main attraction. (I see that Davep’s Astronomy blog makes the same point, and additionally provides some concrete examples of how astronomers can share observation logs.)

  We’ll have to do a proper comparison of all these apps in the near future, and see where the relative strengths and weaknesses are. Luckily, my first love was (and remains) astronomy, so you’re in good hands right here on Ogle Earth:-)

• Web-based Sky? Talking of sky-map.org: Google Earth is to Google Maps like Google Sky is to … ? I’ve been checking during the day whether there might not show up a web-based equivalent of Google Sky at sky.google.com, but no luck…
• Google Sky content contributors: Who were Google’s content partners in bringing the Sky to Google Earth? Google lists them here. It’s a long list with links onwards.
• Google Sky reference links: A resource page by Google about the Sky feature points to a new Google Earth Community forum about Sky. On it you get some interesting bug reports: Here Saturn occults Mercury! (Quite a feat:-) The resource page also sports a YouTube intro to Google Sky. Finally, here is the simple user’s guide for using Sky while here is the advanced KML reference for those who want to put sky data into KML (must-read).
• PhotoOverlay reference links: There’s also an advanced KML guide for using the <PhotoOverlay> tag and one for setting camera angles.

News not specifically about Google Earth version 4.2:

• Embed Google Maps via WordPress: Daniel Denk of Remote Sensing Tools has created a Google Maps plug-in for WordPress that lets you quickly build a map and grab the embedding code while blogging:
  

  While editing your post, you can quickly pop-open Google Maps from the editor and generate your map through the Maps interface, or quickly grab the link to a map you’ve already prepared in My Maps. Then, you can copy the code given for embedding and paste it directly into your editor.

  Fantastic. The YouTubing of Google Maps continues apace:-)

• Google job: Google is looking for a technical writer in London. “Have you downloaded Google products and services such as Google Earth just to play around with them? If so, send us your resume!” I wonder if they would let me work out of Cairo:-)
• Unype + Facebook Unype, which previously let you turn Google Earth into a multi-user environment via Skype (for Windows), now lets you share the space with fellow Facebookers, via an app using the Facebook API.
• Cartoweb KML plugin: exportGge: “A KML export plugin released under GPL license for Cartoweb, an open source web mapping solution working on top of UMN MapServer and written in php5.”
• ArcGIS Explorer goes underground: Re ESRI ArcGIS Explorer’s latest build: It does subsurface navigation, reports Location Based Soup. (Via James Fee Blog). I wonder who’ll be first to do 3D rendering of bathymetry data…
• Geo uses for Amazon S3: Amazon Web Services Blog has an interesting post about all the webistes that are using Amazon’s scalable S3 server to serve map tiles and KML files. It mentions WeoGeo (beta), a site that I had not previously come across which calls itself “a one-stop marketplace for mapping. It supplies surveyors, engineers, cartographers, and scientists with the ability to conveniently store, search, and exchange high-resolution CAD and GIS mapping products. Mappers easily list their data for sale. Researchers quickly find the data they need.” It’s all KML savvy.
• Leica + Microsoft: Leica TITAN, a GIS filesharing and messenger service that lets you share GIS data on a virtual globe, announces that data can now be shared on Microsoft Virtual Earth 2D and 3D. Find out more here.
• Grauniad sics OS: Missed this before: The Guardian covers the story of the UK Ordnance Survey nixing the licensing of data that would have made a 3D model of London in Google Earth possible.