Where on Google Earth #62

With some help from Wikipedia, I found that the image posted by Joe was from a volcanic field in western Sudan. So here comes WoGE #62.

Compared to the Peruvian meanders, this should be easy. Extra points for knowing the story that this place is a good example of — there is a specific journal article I am thinking about.

Schott rule in effect (post time 8:22 pm CST, 10-17-07).

Update: Brian has the answer; here is a bit more detail about this image. It’s the southernmost distributary of the Danube Delta in Romania, called the Sfantu Gheorghe channel. The geometry of the deposits is determined by (1) the river discharge, (2) the wave energy of the Black Sea, and (3) the southward oriented longshore transport. The asymmetry of the lobe is a function of the ratio between the net longshore transport rate at the mouth and river discharge. The longshore currents erode the beach/barrier bars on the northern side of the channel mouth. More details in this paper. This image also comes from Bhattacharya and Giosan (2003):

Black represents sand, gray is predominantly muddy deposits, and the white arrow at the river mouth shows the direction of longshore drift.

Where on (Google) Earth #57

I figured out that the Google Earth image posted by Kim was cut by a famous fault, so I have a chance to post the next installment of Where on (Google) Earth. I don’t think this is easy – it is certainly not a famous geologic locality, and I know it would be tough for me. But I have been interested in erosional meanders for some time, so here you go. North is up.

Update — hint: it is in a forearc basin.

Peyto Lake / Caldron Lake trail

[This is my last post about Peyto Lake, I promise.]

Here is a KMZ (= Google Earth) file for the trail that leads from the Peyto Lake viewing platform to Caldron Lake. It corresponds to the red line in the screenshot below. It is obvious that we never got to Caldron Lake…

You can also see some of the photos in Google Earth, if you download and open this file.

Geologic maps in Google Earth

One of the best ways to really start understanding the geology of an area is to look at the geologic map in Google Earth. Of course, unless you are interested in San Francisco or some other top notch place, you will not find the geologic map available in kmz or kml format (although you can get the whole US geological map here, and they are working on covering most of the globe).

Before that happens however, with a little patience it is possible to draw your own maps in Google Earth. You can use an image overlay as a starting point, and draw polygons on it after you managed to position it properly. As a quick test (well, actually it took me almost one day to do it), I created a small map that covers part of the southern East Carpathians in Romania, an area where I did some work for my thesis. It is based on the Geologic Map of Romania, 1:50000 scale, that is, one sheet from the series, edited by Murgeanu et al. and published in 1968. Old stuff, but good stuff. And a lot of work.

Kovászna és Komandó nagy felbontásban a Google Earth-en

Kovászna, Gelence és Komandó környéke újabban magas felbontásban látható a Google Earth-en. Így néz ki Kovászna, a háttérben a Siklóval (egy egyenes vonal a bal felső sarokban látható hegyen):

A képre kattintva a nagy felbontású fotó is értékelhető. Persze a legjobb ha az ember ezeket a Google Earth-ben nézi.

Georeferencing photos on a Mac

Not long ago I managed to georeference some of my photos using GPS measurements. Before I forget how I did this, here are some notes on the process. The key piece of software is GPSPhotoLinker, written by Jeffrey Early. After downloading and installing this nice little program, the next step is to get the GPS tracks from the GPS unit. For some reason, GPSPhotoLinker did not do this for me; so I downloaded GPSBabel, connected my Garmin Vista Cx to the iMac, and saved the tracks in GPX format. [GPSBabel is the same utility that is used inside GPSPhotoLinker]. I tried to open the GPX file in GPSPhotoLinker, but it did not work. The problem was that some of the tracks on the GPS unit were actually saved — and saving tracks on a Garmin GPS unit (and maybe on other units as well, I don’t know) results in losing the time stamp from each datapoint. GPSPhotoLinker apparently is not able to just ignore this part of the GPX file; the only solution was that I manually deleted all the saved tracks from the GPX file. After that, everything went pretty smoothly. GPSPhotoLinker finds the GPS points that are the closest in time to the time stamp of the photograph and writes the latitude and longitude into the EXIF header of the jpeg file. You can choose between ‘snapping’ photo locations to the nearest GPS datapoint or to interpolate between two points to find the best estimate for the place where the photo was taken. It is important, of course, to record a fairly large number of GPS points when you are taking the pictures.

Once I had the photos tagged with the geographic coordinates, I had two options to display them in the context of a map: either relying on Smugmug, the photo-hosting web service that I use, or on a cool iPhoto plugin called iPhotoToGoogleEarth. With Smugmug, both Google Maps and Google Earth can be used to look at the photos; the drawback is that the displayed pictures are small and you have to go go back to the Smugmug page to see the photos in a reasonable size. The iPhoto plugin generates a kmz file that can be opened with Google Earth and includes all the photos in a reasonable size, that, of course, can be adjusted by the user). The advantage is that you do not have to leave Google Earth in order to look at the photos.

Here is my first try at doing the gereferencing, as shown by Smugmug in Google Maps. It is not a bad idea after all to have a GPS unit handy when you are traveling and taking photos.

PS. In addition to the saved tracks, the other thing that GPSPhotoLinker does not like in the GPX file is the part of the header that refers to the geographic bounds of the file, e.g., “bounds minlat=”-51.725563835″ minlon =”-98.491744157″ maxlat=”43.777740654″ maxlon=”131.500083692″”. You have to delete that in order for GPSPhotoLinker to read the file.

PS 2. There is always more to learn. I thought that the ideal workflow for georeferencing photos would be to (1) do the tagging in GPSPhotoLinker, (2) import the photos to iPhoto, (3) export the ones I want to post on the web, and (4) put them on Smugmug. It turns out this does not work well; all the photos I took in California (and were correctly labeled by GPSPhotolinker) ended up in Kamchatka. The point is that the georeferencing must be done (or redone) after the photos are exported from iPhoto.

Digital Earth

Last weekend I discovered (1) that Google Earth was even more amazing than I had previously thought [and now they have a Mac version as well!]; and (2) there is a lot more out there in terms of digital geography if you look a bit harder.

Here is for example this USGS site from which you can download (with some patience) not only the usual satellite imagery but digital elevation models (DEMs) as well, for pretty much the whole globe [thanks to my friend Radu Girabcea for pointing me to it]. Once you’ve got a DEM, you can use 3dem, a nice little piece of freeware to display the elevation models in 2D and 3D and to drape georeferenced images over the topography. DEMs are available (for free — at least at this point) with a ~10 m resolution for most of the US and a ~30 m resolution for other areas (I was especially excited to savor the detailed topography of the Carpathians — the more familiar you are with a place, the more illuminating it can be if you examine the morphology).

Another thing worth taking a look at is NASA’s version of Google Earth, that is, World Wind. With one click, you can switch from Landsat images to USGS topographic maps [although I often have problems with the server connection]. Can it get a lot better than this?