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Archive for May, 2007

LIDAR Data Coastal Erosion And Flooding Analysis Using MicroDEM

Published by
Leszek Pawlowicz
at May 31, 2007 in DEM, MicroDEM, data and global warming. 1 Comment

LIDAR (Light Detection and Ranging) can be used to create high-resolution terrain data (sub-meter), detail good enough to show individual man-made features like buildings and bridges. It’s especially useful for analyzing terrain in areas that are in constant change, like coastlines. High-resolution coastal LIDAR data is available at this NOAA website for the entire US ocean coastline, and parts of the Great Lakes coastlines, for times ranging from 1996 to the present.

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Cheap Worldwide Road And Contour Maps For Garmin GPS Units

Published by
Leszek Pawlowicz
at May 30, 2007 in GPS and Garmin. 1 Comment

Most handheld Garmin GPS units come with a baseline road map that displays major roads for either the Eastern or Western hemisphere, plus the ability to display greater detail using uploaded map data. Garmin sells a line of CD/DVD disks with data for various parts of the world, and third-party sources offer maps with greater details for specific countries (a Google search should reveal even more). Many of these datasets are expensive, and data is unavailable for some areas of the world. There’s a cheaper option that offers worldwide data, including coverage of areas not covered by commercial products, but with some limitations in quality and detail.

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Animating Sea Level Rise In San Francisco With Vector Overlays In Google Earth In One Word: Don't

Published by
Leszek Pawlowicz
at May 29, 2007 in DEM, Google Earth and global warming. 2 Comments

Last week, I posted the last in my series on animating sea level rise in Google Earth using raster overlays (the “Inconvenient Truth Effect”), and ended with the comment that I would do the same thing with vector overlays, and that doing it that way had some advantages over using raster overlays. Uh, maybe not.

For this effort, I decided to do a vector overlay animation that showed flooding in San Francisco instead of the previous one in Manhattan. Creating a raster animation was pretty straightforward:

Doing the same thing with vector overlays turned out to be a major pain, and even though at first glance the results might look comparable …

… if you look at the results in Google Earth itself, there are big problems with the way it’s rendered at various viewing angles and zoom levels. Read on to find out more.

Continue reading ‘Animating Sea Level Rise In San Francisco With Vector Overlays In Google Earth In One Word: Don't’




Plotting Swivel Data In Google Maps

Published by
Leszek Pawlowicz
at May 28, 2007 in Google Maps and data. 0 Comments

Swivel is a site where anyone can upload data of any kind in tabular or spreadsheet form for general public access, and plot it in a variety of graph formats. Today at Where 2.0, they will announce the new capability of plotting geographic data in Google Maps. See the Webware article for more information and a screenshot. Another more flexible option for this kind of display is Google Map Creator, which creates thematic shapefile maps in Google Maps, but Swivel seems like it may be easier to use.




The "Inconvenient Truth" Effect In Google Earth: Animated Sea Level Rise Flooding Of Lower Manhattan With An Added Depth Effect

Published by
Leszek Pawlowicz
at May 25, 2007 in Google Earth, MicroDEM and global warming. 3 Comments

Yesterday’s post showed how to create a sea level rise flooding animation in Google Earth, like this one:

But if you downloaded the KMZ file used to create this animation, and ran it with 3D buildings turned on at the tip of Manhattan, the final image you’d get with 12 meters of flooding looks like this:

downtownnoheight

And there’s a problem with the accuracy of this image: there’s no actual depth to the flooding, i.e. the lower levels of the buildings aren’t covered with water. In fact, some of the buildings you can see in the view above would be completely covered with water if this were a more realistic depiction. That’s because no absolute altitude was assigned to the image overlays used in creating the animation, so they are “clamped” to the terrain level. But by assigning a height to every overlay image in the animation, one can create a realistic effect where the flooding doesn’t just cover more area as the sea level rises, but covers the bottom levels of some buildings, and completely covers other ones. This would be similar to the animations shown in the movie “An Inconvenient Truth”, and in one sense even better. In that movie, the flooding was show in overhead views, while the Google Earth animation can be viewed at an oblique angle of your choosing, with 3D buildings.

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National Solar Radiation Database

Published by
Leszek Pawlowicz
at May 24, 2007 in data and global warming. 0 Comments

The National Solar Radiation Database offers solar radiation data and limited meteorological data for 237 sites in the US over the period 1961-1990, and expanded data for 1454 sites from 1991-2005:

nsrdb_map_w61-90

Data includes:

  • Hourly Solar Data
  • Statistical Summaries
    • Daily Statistics Files
    • Hourly Statistics
    • Threshold Files
  • Solar Radiation Data Manual for Buildings
  • Solar Radiation Data Manual for Flat-Plate and Concentrating Collectors
  • Typical Meteorological Year (TMY2) Files

    • User manuals in PDF format can be downloaded. Data is in text format, but can be converted to spreadsheet format with a bit of work.

    Via Treehugger.




    High-Resolution Sea Level Rise Flooding Animations In Google Earth

    Published by
    Leszek Pawlowicz
    at May 24, 2007     in Google Earth, MicroDEM and global warming. 7 Comments

    Creating a high-resolution static sea-level rise image for a specific sea level rise value, and displaying it in Google Earth, is fairly straightforward (see these three posts for the details):

    geoverlay1

    But creating an animated version viewable in Google Earth, comparable to this animation created in MicroDEM …

    … takes a bit more work, including diving into the KML code. But while it’s a bit time-consuming, it’s not that hard, and the results are worth it:

    Addendum: Do read the rest of this post, but also check out the next post in the series as well for even cooler effects.

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    Adding Vector Graphic Objects To Google Earth

    Published by
    Leszek Pawlowicz
    at May 23, 2007     in Google Earth. 0 Comments

    This is a minor addendum to the previous post on creating and placing arbitrary raster graphic images and symbols into Google Earth using GIF/PNG transparency. As my chicken scratch writing sample showed, creating quality raster graphic symbols can be a challenge for some, and while there are tools in most raster graphic editors to create high-quality test, shapes and symbols, vector drawing programs usually do a better job on those. It’s possible to use a slightly-modified version of the process in the previous post to bring symbols drawn in vector graphic software into Google Earth.

    1. As before, export in image format the area of Google Earth you want to display custom graphics on top of, recording the bounds of the image.

    2. Import this graphic jpg image into a vector drawing program. Adobe Illustrator is the best-known COTS program for this, but if you search around, you can find several free programs that do similar things. Examples include Inkscape, a simple, free and open source solution, and Creature House Expression 3, a commercial program now available for free that is very powerful, but has a steep learning curve.

    3. Mark the corners of the imported graphic with some kind of symbols; you’ll need these as a guide to cropping later on.

    4. Add your vector objects in the appropriate position on top of the raster graphic image from Google Earth.

    5. When you’re finished adding vector objects, delete the raster graphic image, leaving behind the vector objects.

    6. Export this image as a raster graphic (check your help file to find out how). You’ll get the best results by saving it in a lossless format like TIFF, PNG, or GIF (the last only if the image has less than 256 colors).

    7. Open the new raster graphic image in your favorite raster graphic editor, and crop it using the bounds from step 3 as guides.

    8. If the resulting cropped raster graphic image is large (greater than 2000 x 2000 pixels), Google Earth may have trouble dealing with it; use the resize function to shrink it down, then save it

    From this point on, just follow the steps in the previous post to convert this graphic image to a GIF/PNG file with transparency, and then to place it correctly in Google Earth. Unlike the raster graphic example in the previous post, you may have to move and stretch the image a bit to get it place correctly, depending on how accurately you were able to crop it in step 7.




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