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Archive for the 'MicroDEM' Category

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:

drmsstatus

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

commstatus

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:

iconcomposer1

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

iconcomposer2

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:

raster

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:

mapwithicons

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):

drmsraster

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

drmsvector

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.).




Get DEM Elevations For A List Of Points

YP asks:

…would you know an easy (and free) way to query a DEM (Digital Elevation Model) to get elevations for a list of points (potentially as many as a few thousand)

Well, I know one way to do it with free software:

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Options For MGRS Coordinate Conversion And Viewing

My visitation logs show a surprisingly large number of visitors interested in converters for the Military Grid Reference System (MGRS), the standard geocoordinate system used by members of the NATO Alliance. So I thought I’d do a quick roundup of previous links/posts related to MGRS, and then talk about another program that might be useful if you’re working in that coordinate system.

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Creating "Transparent" Topo Map Overlays For Google Earth

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:

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Google Earth Ground Overlays With GIF Transparency

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):

Terrain shaded topo map 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:

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Creating Google Earth Ground Overlays From Georeferenced Images

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

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Goofing Around With Pan-sharpening

Orbiting satellites often have two types of digital imaging sensors:

- Multispectral, i.e. different sensors for different colors (including IR), or different filters in front of the same sensor. Each individual band can be shown as a black-and-white image; multiple bands can each be assigned a color, and combined to form an RGB color image.

- Panchromatic, “meaning all the colors”, a single broad-spectrum sensor. This are usually displayed as a monochromatic image (i.e. black-and-white).

The panchromatic sensors usually have a higher spatial resolution than the multispectral. For example, on the Landsat 7 spacecraft, the 6 multispectral bands have a spatial resolution of roughly 30 meters (a seventh has 60 meters), while the panchromatic sensor has a resolution of about 15 meters. Here’s an example of an image created from three of the Landsat multispectral bands (data from the Global Land Cover Facility):

Continue reading ‘Goofing Around With Pan-sharpening’




Embedding And Extracting Worldfiles With MicroDEM

As described in a previous post, the TatukGIS Viewer has the ability to open image files along with their associated worldfiles, and then convert the image to a GeoTiff with the worldfile georeferencing data embedded it. It can also open a georeferenced image file like a GeoTiff or MRSid, and then save it in JPG, PNG, BMP or TIF formats while creating an associated worldfile. The two biggest drawbacks are that it stamps every exported image at the bottom with the message “Exported with the TatukGIS Viewer www.TatukGIS.com” in yellow-accented letters, and it can’t embed coordinate system and datum data in the GeoTiff (e.g. UTM, WGS84). MicroDEM can’t do everything that the TatukGIS viewer can, and isn’t as easy to use. But it has the ability to convert image files with worldfiles into GeoTiffs, and export image files with worldfiles, but without the stamped message at the bottom. It also has a limited ability to embed coordinate/datum data into the GeoTiffs along with the georeferencing data.

To convert an image file with a worldfile:

1. From the File=>Open menu, choose either “Open image” or “Open scanned map”

2. From the “Files of type” dropdown, choose “Imagery with world files”

3. Select the worldfile for the image you want to open (e.g. *.tfw, *.jgw, etc.)

4. The “Pick Projection Parameters” window will open. Here you can select the datum for the data, and the UTM zone for UTM coordinates. If the worldfile is in geographic coordinates (lat/long), the UTM Zone setting is irrelevant.

Capture8-14-2007-1.31.17 PM8-14-2007-10.47.04 PM9-11-2007-7.24.32 PM

5. Click OK, and the image will open onscreen, fully georeferenced. If you only want to export part of the image, you can select it with the subset and zoom button on the toolbar:

subsetandzoom

6. MicroDEM saves images in the screen resolution; to save in the full native resolution, you’ll have to zoom to 1:1; to do that, click on the “No zoom (1:1)” toolbar button:

zoom1to1

7. Choose File => Save map as image => GEOTIFF, screen scale. This will save the image as a GeoTiff, with the georeferencing data embedded, and with the coordinate system and WGS84 datum information also embedded. And no watermark stamp.

Limitations:

- JPG, BMP, GIF and PNG supported natively; MRSid is supported with add-ons, but isn’t easy to work with. Search the help file for “MRSid” for more info on how to set this up in MicroDEM.

- The only coordinate systems supported are geographic and UTM; no Lambert, SPCS, etc..

- The only datum data is exported in is WGS84, regardless of what datum the original data was in, and which datum you specified in step 4 above.

- GeoTiffs are exported in 24-bit color; 8-bit or indexed color is not supported.

If you want to go the other direction, converting a GeoTiff or MRSid file with embedded geodata into an image format with worldfile:

1. Open the GeoTiff/MRSid in MicroDEM

2. Select File => Save map as image => With worldfile

3. Select the desired image format (BMP, PNG or JPG), and save the file. The worldfile will be created automatically in the same directory.