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Archive for the 'Google Earth' Category Page 3 of 25

Multiple Embeddable Web Maps With Switch Maps

New from MapChannels is Switch Maps, an easy way to embed multiple web maps in a single frame. A simple web interface lets you set the geographic extents, size of the map frame, and which maps to include:

Continue reading ‘Multiple Embeddable Web Maps With Switch Maps’

Natural Earth Data In Google Earth

Last week, I posted about the new Natural Earth datasets, free medium-scale vector data for the earth to go along with the previously-available Natural Earth physiographic raster data. The Google Earth Library now has a KML network link that lets you view much of this data in Google Earth as layers, like here with lakes and rivers:


Obviously, most of these features will be visible in Google Earth as soon as you zoom in, but these datasets let you view features with names at lower zoom levels, and more distinct colors. Plus, this offers a quick preview of the data available from Natural Earth, so you can see whether it meets your needs for use in a GIS or mapping program in shapefile format. There’s also an overlay with the raster physiographic imagery:


All of the data is in KML network links in subfolders of the main link, and some datasets will take a while to load. It’s also probably a good idea to not check the box next to the main network link, as this will load all the data into Google Earth, which will take a while.

Create KML Range Circles, Arrows And Wedges With An Excel Macro

I’m currently running OpenOffice only, so I can’t try it out, but “Planeman” has created an Excel macro that will create KML range circles, arrows and wedges for a list of decimal latitude/longitude points. Should be able to create these for hundreds or even thousands of points simultaneously. Pictures are from Planeman’s description. Excel spreadsheet view:


And a view of the results from the sample data in Google Earth:


Download the spreadsheet macro at this link; be sure to scroll down to the bottom to get the latest version. From the picture above, looks like additional features are coming soon.

Draw Freely On Google Maps, Export In Multiple Formats

ScribbleMaps is one of the slickest Google Maps apps I’ve ever seen. Draw and/or place any of the following on a Google Map view:

  • Freehand lines
  • Straight lines
  • Circles
  • Rectangles
  • Arbitrary shapes
  • Text
  • Images (needs a web link to the image)
  • Standard Google Map/Earth placemark icons (select from multiple sets):


You also have control of the color, opacity and line thickness from the toolbar, along with the ability to search for locations:


Once the shapes are created, you can move them, modify them by shifting vertices, rotate them, or erase them. Once done with your map, you have multiple export options:

  • JPEG
  • Print directly from browser
  • Embeddable widget (no Google Maps API key required):

  • Facebook map
  • Regular Google Maps view
  • Google Earth plugin (though this didn’t work for me)
  • KML file (for viewing in Google Earth)


  • GPX (for export to your GPS); only exports points and lines, the only geometric shapes that GPX files support

You can also save your map for future editing, and get a dedicated web link for it; you choose a password for it so that only you can edit it, or delete it later.

Very slick, and very cool; I’m putting ScribbleMaps into my main bookmarks list.

Create Garmin-Compatible Raster KMZ Files From Georeferenced Imagery With G-Raster

Garmin recently announced support for raster imagery like aerial photos and topo maps for some of their handheld GPS units, specifically their newer product lines: the Colorado, Oregon, and Dakota series. See recent posts at GPS Tracklog and GPS Fix for more information on this new feature. It requires download and installation of beta firmware on your Garmin GPS unit, and conversion of the raster images to a compatible format. Fortunately, the compatible format is the open format KMZ image overlay, which can be created in Google Earth:

  1. Zoom to the desired location in Google Earth
  2. Load the map or aerial image as an Image Overlay
  3. Calibrate the image by manually positioning, rotating and resizing it until it corresponds to the underlying Google Earth imagery.
  4. Save it as a KMZ file.
  5. Copy it to the \Garmin\Custom Maps folder on your Garmin GPS unit.

A fairly straightforward process, but there are some drawbacks:

  • The image must be no larger than one megapixel in size (1024 x 1024; 2048 x 512; etc.)
  • You can chop an image into subsections/tiles and combine them into a single overlay file, but this requires individually calibrating each tile
  • You can have no more than 100 such tiles loaded onto your GPS unit
  • If you have an image that’s georeferenced with either embedded geodata (like a GeoTiff, ERDAS Imagine, MRSID or BSB file), or a worldfile, there’s no way to use that georeferencing data, and you have to manually convert the file to JPG format

I’ve just finished version 1.0 of G-Raster, a utility that helps solve some of these problems:

  • Loads map/aerial imagery files with embedded geodata or worldfiles
  • Automatically extracts the geographic data, and optimally reprojects the image
  • Chops images larger than 1 megapixel into smaller subtiles, and calibrates all of them
  • Converts the image into JPG format
  • Creates a KMZ file that can be copied over to your Garmin unit

You can find the link to the latest version of the program installer here (look for the G-Raster download link, then the link that says “Click here to start download”). Once installed, run the program, and it will walk you through the process step by step.


Step 1: Loading The Data

G-Raster accepts four basic types of georeferenced raster imagery:

Type 1: Files with the geographic data embedded in the graphic file itself. These include:

  • GeoTiffs: TIFF images with embedded geodata
  • MRSID imagery (file extension .sid or .mrsid)
  • NOAA BSB imagery (file extension .kap)
  • ERDAS Imagine format (file extension .img

Note: These must include all geographic data, including the type of coordinate system used. A great source for free USGS topo maps and aerial imagery is the USGS Seamless Server, which offers this data in the compatible GeoTiff format. Links to that site and other useful sources of data are available from the program menu.

Type 2: JPG imagery (“Big JPEG”) generated by the free program USAPhotoMaps. You will need to specify the UTM zone for the map you want to use.

Type 3: General graphic files with geodata in worldfile format for the UTM coordinate system (e.g. JPG with .jgw, BMP with .bpw, GIF with .gfw, TIF with .tfw). You will need to specify the UTM zone for the map, and also the datum and hemisphere if appropriate (default is northern hemisphere, WGS84 datum)

Type 4: General graphic files with geodata in worldfile format in any coordinate system. But you will have to: a) Know what that coordinate system is; b) Look up its EPSG code; c) Enter the code in the specified box

The process is easiest for Type 1 files; click the “Load …” button, and choose the file you want to create a KMZ overlay for. The program will automatically process the file, and take you directly to Step 3.

For Type 2 files, you will need to select the JPG file created by USAPhotomaps, normally placed into that program’s main directory. You will also need to specify the UTM zone for that map; you can get this information from USAPhotoMaps directly by choosing View => LatLon => UTM from the menu when viewing the maps you want to use; the UTM zone will be listed at the top. Alternatively, try one of the links under the UTM/EPSG Info menu. G-Raster will highlight the input section in red to remind you that it needs that data:


The process is similar for Type 3 files, except that you’ll have more choices for types of graphics (JPG, TIFF, BMG, GIF), and in addition to the UTM zone you’ll need to make sure the correct datum and hemisphere is chosen.

The process for Type 4 files is like that for Type 3 files, except that you will need to enter the EPSG code for the data in question.

Step 2: Process the raster graphic

After you enter the required data for files of Type 2-4, the button marked “Process Raster Graphic” will be enabled. Click on this button to start the process of converting the map graphic into the correct format. When it’s complete, a message will show up in green directly below this step, and the “Create KMZ File” button will be enabled. You can now go to Step 3

Possible problems:

– If the file is larger than 100 million pixels, it will be impossible for the program to process it as is; you’ll have the option of cropping the outer edges of the picture to bring it down to an acceptable size, but this will eliminate the map image data at the edges.

– In rare cases, an image close to but just below the maximum pixel count may not be able to be chopped up into 100 tiles or less. Future versions of the program will offer you the chance to resize the image slightly to fix this problem, but for now, you’ll have to crop or resize the image yourself.

Step 3: Set Parameters For KMZ Files

You’re almost ready to create the KMZ overlay file, but there are several options you might want to change:

KMZ Filename: The final output file will be saved using the name specified here in the same directory as the graphic file used to create it. Default is “Overlay_name”, and I’m assuming you’ll want to change this. If you choose a name that corresponds to a file that already exists, you’ll get an error message when you try to create the file.

JPG Quality: The output imagery is required by Garmin to be in JPG format. You can adjust the quality of the image from highest (100) to lowest (50 here) to reduce the total filesize, which may improve speed. Garmin’s recommended JPG quality number is 80, but you can experiment with lower/higher numbers to see which works better for you. One possible complication: the maximum image filesize is 3 MB, and in very rare circumstances choosing a high quality (98-100) might result in a tile that’s too large. Wouldn’t worry about it, but it’s something to keep in mind.

DrawOrder: Garmin offers two options for viewing the raster imagery. With On Top, the raster image displays above everything else, including any loaded vector maps. With Below Vector, the raster map still sits on top of some vector imagery (like lakes and parks), but can have other vector data on top of it (like roads and contour lines).

50% Transparency In Google Earth: Makes the overlay partially transparent in Google Earth, to help with determining whether it’s lined up correctly with underlying imagery. Has no effect on the map’s appearance in the Garmin unit’s display.

Rescale Factor / Rescale Image: Rescales the image to a smaller size based on the rescale factor entered ( > 1 only). For example, a rescale factor of 2 resizes the x and y dimensions by two, making the image a factor of 4 smaller in total pixel size. The advantage of this is to reduce the total number of tiles required to cover the image, in case you want to create multiple overlays with a total number of tiles less than the maximum 100. The disadvantage of this is that you will lose some image resolution, but depending on the Garmin zoom level you view the image at, you might not even notice the diminished resolution.

Step 4: Create KMZ File

Once you’ve set the parameters at left as desired, click the “Create KMZ File” button, and in a few seconds a message will pop up telling you that the KMZ file has been created in the same directory as the original graphic file.

If you like, you can now change some of the parameters, and create another KMZ file; this way, you can experiment with different settings. Just be sure to specify a different name for every one.

Step 5: Check the file in Google Earth

IMO, this is a mandatory step – you have to make sure the map is positioned correctly before trying to use it in your Garmin GPS unit.

You should have Google Earth installed on your computer for this step; if you don’t, go to the Google Earth website, and download/install the program on your computer. You can then double-click on the KMZ file created in Step 4 to load it into Google Earth. The KMZ overlay will be listed in the “Temporary Places” section of the info pane at left, and Google Earth will automatically zoom into the area covered by the map. Clicking the checkbox next to the overlay name will turn the image on and off, helping to see if it lines up correctly. If you chose 50% transparency as an option, the map image will be slightly transparent so that you can see what’s underneath – this may help you see how well the image is placed:


Depending on your location, you may notice a shift in position between the KMZ overlay and the underlying imagery of anywhere from 0 – 100 meters, with 10-20 meters being common for the US. This is not an indication of an error in the overlay, but rather a reflection of a fundamental limitation with Google Earth. The geographic position of Google Earth imagery isn’t always 100% accurate; see this post for more info. Unfortunately, there’s no way now to know how far off the imagery is shifted, which in turn imposes a limitation on how confident you can be that your overlay will be calibrated correctly in your Garmin unit.

Step 6 – Load The Overlay For Use In Your Garmin GPS Unit

Until the Garmin firmware is out of beta, I strongly recommend that you only install KMZ files on an external memory data card, not in the internal memory of your Garmin unit. This way, if there’s a problem, you can fix it by removing the card.

1. Take the external card, and put it into a separate card reader (not the Garmin itself). It will show up on your computer as a separate drive.

2. Open the drive, and go to the \Garmin\CustomMaps folder (if it doesn’t exist, you’ll have to create it)

3. Copy the KMZ raster overlay file into this folder.

4. Install the external memory card into your computer.

5. Follow Garmin’s instructions on its use, including turning it on and off.

In my next post, I’ll offer some tips and tricks to make the most of G-Raster.

Additional support for this new Garmin feature is available at the Garmin Custom Maps forum, including a helpful post if you have problems after installing a map.

Convert From AutoCad Format To KML And Vice Versa With KML Tools Pro

I don’t have AutoCad, so I can’t try this out, but KML Tools Pro has AutoCad DVB macros that let you select features in AutoCad and convert them to Google Earth’s KML format; similarly, another macro will let you import a KML file into AutoCAD. From the website:

From AutoCad to Google Earth:

  • select objects and create .kml file
  • export points, lines, text, polygons (beta)
  • apply the icon of your choice
  • select zoom level that objects are visible
  • output automatically layer colors
  • adjust weight and transparency of objects

From Google Earth to AutoCad:

  • digitize points, lines, polygons in GEarth
  • save “.kml”
  • import in AutoCad using wanted projection

Supported projections:

  • NAD-83′ State Plane (*Alaska Zone 1 not supported)
  • UTM zones
  • HATT
  • Greek Grid (EGSA 87)

The current download site is in Greek, but the link to the downloadable file is obvious at the bottom. An older version of the page used to be available at this link, but isn’t currently working; you might try the cached version of the page from Google.

For converting KML files to DXF format, you can also try this online converter.

Disaster Response Map Symbols

The Portuguese chapter of the Association Of Volunteer Emergency Response Teams, in collaboration with Peter Guth and Donald Springer, is working to create a general-purpose set of symbols useful in mapping the position and condition of infrastructure, resources and incidents during emergency situations. You can download these Disaster Response Map Symbols as a True Type font from the DRMS website, along with a PDF file that documents the symbols There are 253 symbols depicting infrastructure, resources and incidents (graphic from the help file for MicroDEM, Peter Guth’s freeware GIS):

drms table

And additional dot symbols that represent the status of the higher-level symbol:


These status symbols would be plotted directly below the higher-level symbol, to indicates its condition/status:


Any GIS software that can use True Type fonts for symbols or labeling can use the DRMS symbol set directly. But MicroDEM has some special capabilities built in for working with this symbology. Make sure you’ve used the most recent program install, which includes the DRMS True-Type font; also, download the latest executable and copy it into the program directory.

From MicroDEM’s File => Tools menu, selecting Military icon generator brings up the icon composer window; make sure the DRMS tab is selected:


Double-click on an icon to select it, and then modify it as you like:

  • Use the color button to modify the color
  • Use Left/Right/Top/Bottom to add text around the symbol.
  • Select the Infrastructure status to plot dots depicting the status of the feature underneath the symbol
  • Modify the test and symbol size using the arrow keys


Once the symbol design is complete, you can save the symbol to the clipboard to paste into a graphics program, or choose “Save to file” to save it as a PNG, GIF, JPG, BMP or Targa format graphic file for those GIS programs that let you select graphic images to represent points.

You can also plot these symbols directly on a map in MicroDEM. Open up a georeferenced raster image in MicroDEM:


Clicking on the Map Annotation button on the toolbar (second from the left), choose Military icons from the drop-down, and then enter a filename to save the locations for the icons you want to place. You’ll then use the same Icon Composer interface as above to design your DRMS icons. The Left text is used as a feature ID in the DBF file, and also in the KML file you have the option of creating later on. Once you’ve designed your icon, you can double-click on the raster map to place the icon on that map:


Click on the “Close” button in the Icon Composer when you’re done. You can now export this map image directly to a generic image file or GeoTiff using the appropriate File => Save … option. But by right-clicking on the map, choosing Load => Google Earth overlay, you can export both the raster image and vector points to Google Earth. Here’s the raster overlay in Google Earth (vector overlay is turned off):


And here are the vector points, with the selected icons, for the same area (raster overlay turned off):


These data files are loaded into Google Earth automatically, but they’re not saved; to keep them for future use, right-click on the dataset listed in the Google Earth Places pane, choose “Save Place As”, then save it as a KMZ file.

Closing the Icon Composer will also open up a DBF  table window with the locations of the points you’ve just created; you can convert that to a point shapefile by clicking on the Report button, then selecting point shapefile. There’s also an option with this Report to create a KML file, but make sure you save this KML file in an empty folder. As I found out by testing it, this option creates a KMZ file, copies every single file in that folder into the KMZ file, then deletes the original file from the folder. If this happens to you, rename the KMZ extension to ZIP, then use your favorite unzipping program to extract out the original files. Also, the KMZ file contains only the KML text data, which  references the graphic icon files in a local directory on your computer for display in Google Earth. If you want to save this file for future use on your computer or another computer, and keep the graphics, you will need to open the file immediately in Google Earth, then save it as a KMZ file (right-click, choose “Save Place As”,etc.).

LandSerf – Google Earth And GPS Functions

In previous posts, I reviewed LandSerf’s raster terrain analysis functions and vector functions. Today I’ll wrap up with a short review of LandSerf’s Google Earth and GPS functions.

Google Earth: The most notable Google Earth functionality is the ability to export vector data, either imported or generated by the program, into KML vector files. So I can open a DEM, like the sample one of Mt. Rainier included with the program:


Generate a set of flow vectors for the DEM:


And then export the vector data as a KML file:


You could do something similar with a shapefile opened in LandSerf, but just be sure the shapefile is in NAD83 or WGS84. As I mention in the post on LandSerf vector functions, LandSerf has problems re-projecting from one datum to a significantly different second datum, and Google Earth data needs to be in WGS84 (NAD83 is almost the same). A search for “KML shapefile” on this blog will bring up a number of other programs that do a better job of converting shapefiles to KML, including preserving attribute data, which LandSerf doesn’t. But all of those are Windows-based; LandSerf runs on Macintosh and Linux, so it might be a useful option for those OSes.

Note: You should save vector data as a KML file; the KMZ file format is supposedly reserved for saving raster data as Google Earth image overlays, but I’ve been unsuccessful in getting that to work.

GPS: The list of useful GPS functions in LandSerf is a bit longer:

  • Convert loaded shapefiles or other vector data to GPX format (data must be in WGS84/NAD83 datum)
  • Load a GPX file as vector data, then save it in any of the vector formats LandSerf supports
  • Interface directly with a GPS. You’ll need to have the GPS connected to your computer and turned on before starting up LandSerf. To establish a connection to the GPS, use Configure=>GPS and scan for a connected unit. Once you do this, you can import waypoint data using the File=>Import from GPS function. While the dialog box gives you the option to import waypoints, tracks and routes:


I’ve had difficulty getting tracks to import successfully – the program just shuts down on me. This may just be an issue with my model GPS (Garmin 60Cx); f you have better luck, let me know. You can import the data in the default lat/long coordinate system. or re-project it on import to OSNG or UTM. Once there, you can export it in GPX, shapefile or other vector format.

  • You can also export point data (no lines or polygons) directly from LandSerf to a connected GPS as waypoints.

If you can get track data to import successfully from your GPS to LandSerf, which I couldn’t, there are several other functions that might prove useful:

  • On importing the data, you have the option of saving all the track data in spreadsheet format with position, elevation and time
  • As with other vector data, if you have a digital elevation model loaded in the program, you can get a elevation profile plot; see this previous LandSerf post for more info
  • If you have a GPS track that is broken into .segments because you lost the GPS signal, LandSerf has the ability to join all of the line segments into a single line, which you can then save as a GPX track file, using the Edit => Join vector lines function. AFAIK, it’s the only free program that can do this.

As with the Google Earth functions, there are other programs that can do most of this in Windows, but far fewer free options in Macintosh and Linux.