In a previous post, I used MicroDEM’s ability to create GIF Google Earth overlays with transparency to create selective overlays of MicroDEM terrain analysis products. But you can use this ability with any georeferenced raster image, including topo maps, as long as the areas of the graphic you want to have transparent are white. One example would be USGS 24K topo maps, but these often have large areas that aren’t white, as in this case:
Continue reading ‘Creating "Transparent" Topo Map Overlays For Google Earth’
In a previous post, I talked about using MicroDEM to easily create Google Earth ground overlays, images draped over Google Earth terrain in the correct position, like this terrain-shaded topo map (viewed in Google Earth):
But you can also create a Google Earth ground overlay in MicroDEM as a GIF with transparency, where any part of the image that’s white will be invisible in the Google Earth overlay. There are a number of MicroDEM analysis functions that can produce a graphic product with the data product in color and the background in white. One example would be the terrain category function, where you can select parts of terrain based on parameters like slope, elevation, aspect ratio, and relief. Suppose I have a DEM displayed in reflectance mode:
Continue reading ‘Google Earth Ground Overlays With GIF Transparency’
In Google Earth, a ground overlay is an image that’s been imported into the program and “draped” over terrain as a substitute for the default imagery. In the Free and Plus versions of Google Earth, you have to position the overlay manually to put it in the right geographical context, stretching and rotating it until it’s properly positioned. Google Earth Pro is able to open some kinds of georeferenced images (like GeoTiffs), and automatically drape them in the correct geographic position, but at $400 it’s not for everyone. The free GIS program MicroDEM has recently added the ability to automatically create a Google Earth overlay from any georeferenced image it can open, including GeoTiffs, and formats like JPEG and BMP if they have worldfiles associated with them
Continue reading ‘Creating Google Earth Ground Overlays From Georeferenced Images’
Google is starting a series of online workshops and lectures for geo-developers. First two events:
Feb. 20 @6pm: Quick & Dirty KML Creation
Feb. 27 @6pm: Creating Custom Maps
Register online at the above link if you’d like to attend in person; space is limited. Lectures/workshops will be posted on YouTube afterwards.
Via GoogleMapsMania.
The Map Room posts on the University of Toronto’s efforts to put the three-volume Historical Atlas of Canada in online format; it’s not complete yet, but still worth a look. Maps and graphics don’t appear to be downloadable, but some of the data is (e.g. climatic data). Screen grab:
Native Subsistence 1000 CE to Contact
Matt Perry posts on the release of a 4-year effort he’s been part of to map the effects of mankind on the marine ecosystems of the world. Links on his page point to the announcement article in Science Magazine, media coverage, and the UCSB Global Map of Human Impacts to Marine Ecosystems website that has downloadable KML and raster data for this information. This is incredibly important work, and the results are sobering:
The US Government’s National Oceanic And Atmospheric Administration (NOAA) has placed online 21,000 maps, downloadable in both JPG and MRSID high-resolution formats (see this post for several free MRSID viewers and converters). The maps are mainly historical nautical maps dating from 1655 to 2001, but there are also a fair number of Civil War battlefield maps, many of them contemporary with the war, and not all of them nautical in nature.
Continue reading ‘Historical Nautical And Civil War Maps’
Published at February 13, 2008
in GPS and Garmin.
In the comments to a previous post, someone asked if there were any place where you could find a legend for Garmin GPS unit waypoint icons. I pointed him to this Garmin page, which has a partial legend for Garmin MapSource icons, but it turns out that MapSource icons don’t always resemble the corresponding icons on a Garmin GPS unit.There’s no legend for Garmin GPS unit waypoint icons anywhere else that I could find, either on the Web or in Garmin’s own documentation. For future reference, I’ve put together the following tables of Garmin waypoint icons by category. This is how they’re displayed on my Garmin 60Cx, but they may well be different on other Garmin models. In parentheses below the label is the MapSource Symbol category which contains this icon. If your unit has different or additional icons, and you can send a copy of them to me, I’ll add them to this post.
Continue reading ‘Garmin GPS Unit Waypoint Icons Table’
