The following review was contributed by Leszek Pawlowicz.

MicroDEM is the product of over twenty years of work by Peter Guth, Professor of Oceanography at the US Naval Academy in Annapolis, MD. It contains a staggering number of options and functions, to the point where it may be overwhelming to the new user. But stick with it ...you're almost certain to find multiple functions that are unique to it, or that you'd have to pay quite a bit of money to duplicate with other software. MicroDEM is 100% free.

There are at least three versions of MicroDEM currently available:

MicroDEM 5.1: An older version from 2001, back when it was also being supported by the US Army as "Terrabase II". Available from Fort Leonard Wood (http://www.wood.army.mil/TVC/DefaultPageContents/MicroDEM_TBII.htm). May work better for slower computers.

MicroDEM 6.03: The last official and fully debugged version of Terrabase II; contains most of the functions of version 5.1, plus many new ones. Available at http://www.wood.army.mil/TVC/DefaultPageContents/MicroDEM_TBII.htm

Microdem 7/8/9: Successive versions of MicroDEM have been released as alpha software, with version 9 first appearing in September 2005. As alpha, the software does have bugs and quirks, but it also has far more features than version 6.03. Available at http://www.nadn.navy.mil/Users/oceano/pguth/website/microdemdown.htm. There is a full setup file for version 9 that is updated every few months; updated versions of the executable and help files are released on a fairly regular basis.

Tip: You can have different versions of the software installed on the same computer (e.g. both version 6.03 and version 9), but it's probably best to install the older version first so that the data folder is updated properly for the newer version upon installation.

Documentation: Extensive documentation exists for the older versions, most of which is applicable to the most recent version as well. PDF manuals for versions 5.1 and 6.03 are available at http://www.wood.army.mil/TVC/DefaultPageContents/MicroDEM_TBII.htm, as are short video demonstrations of many of the functions. Tip: Make sure you install the Camtasia Codec, available at the site, in order to view the videos. Both versions 5.1 and 6.03 come with large help files as part of the installation. There is no corresponding PDF manual for version 9, but the help file is large and generally comprehensive, though newly-added functions may take some time to be fully documented.

Professor Guth also maintains a MicroDEM forum on Delphi (http://forums.delphiforums.com/microdem/start), where you can post questions and bug reports.

MicroDEM Panorama

MicroDEM Capabilities

There are simply too many capabilities in MicroDEM to describe all of them fully. What follows is an incomplete listing of many of its current capabilities. The program's help file has more information. The functions listed are those available in version 9; many, but not all, are also available in version 6.

2-D DEM display and analysis:

MicroDEM can directly read in DEMs in many standard formats, and also includes converters for other formats that it doesn't support natively. It also writes DEMs in several different formats, including GeoTiff, ASCII, DXF and ArcGrid. MD will re-interpolate DEMs to UTM or geographic coordinates with the spacing of your choice.

Tip: MicroDEM will save DEMs in .DEM format, but it's a native format that many other programs won't recognize (one exception is Global Mapper).

Reflectance:

• Variable sun angle and altitude
• Variable vertical exaggeration
• Choice of aspect-based shading or sun angle shading
• Coloration in greys, blue/green, six colors, and IHS
• Automatic water coloring for flat areas / sea level
• Blue/red stereo anaglyph with user-adjustable exaggeration

Slope/cant:

Six display variations from Display Parameters

• Standard (with user-definable colors for slope ranges)
• Trafficability (pre-defined colors)
• Gray-scale
• Rainbow
• Pastel
• Go/No Go

Three display variations from Tinted Maps

• Slope %
• Slope degree
• Slope sine

Aspect (which compass direction the slope is facing): Available in two different forms from the Display Parameter menu and the View => Tinted Maps => Aspect menu

Blank: Useful when viewing or saving overlays

Additional options from Tinted Maps include:

• Relief
• Profile convexity
• Plan convexity
• Cross-sectional curvature
• Minimum curvature
• Maximum curvature
• Openness upwards (positive)
• Openness downwards (negative)
• Ridges
• Summits
• Base level

Tip: If you export an image from MicroDEM, it will be in screen resolution; to export in full resolution, make sure you zoom the display to 1:1 using the "1" button at the top of the map display.

Terrain categories: Creates an overlay for a specified range of parameters, including slope, elevation, aspect and relief. For example, you could find all areas on DEM with slope between 20 and 45% on north-facing slopes above 3000 feet.

Drainage basin: Works with TARDEM to do drainage basin operations. Under this menu item, will also plot downhill vectors on DEMs.

Contours: Calculates and displays contour lines with user-definable spacing and colors

Elevation extremes: Locates all points between user-specified values

Slope calculations:

• Finds slope between two specified points
• Finds excessive and steepest slopes on DEM
• Calculates slope at a particular point

Intervisibility options:

Program author is actively working on these functions, and they may or may not be working with any particular build of the program:

MicroDEM Line-of-Sight (slopes in green are visible from the selected vantage point)

• Line-Of-Sight (LOS)
  • Calculates LOS graph between two user-specified points
  • Plots visible as green, invisible as red
  • Moving mouse cursor along graph moves corresponding cursor along DEM display
  • Calculates parallel profiles
  • Also available for arbitrary shape as Stream Profile
• Weapons Fan (aka Viewshed)
  • Calculates area visible from a specific point on DEM
  • User-adjustable ranges, elevations
  • Plots visible, hidden or both with user-specified colors and opacity
• Horizon calculations
  • Calculates angle and distance of horizon blocking, plots on DEM
  • Calculates sun blocking for any day or days of year (when sun is visible or masked by topography)
  • Creates sunlight visibility DEM maps for user-defined area for any day/days of year (very slow)
• Route coverage
  • Shows what areas are visible as you travel along a route, as a static map and animation
• Target coverage
  • Calculates percentage of a target area visible from a specific point
• Route observation of target
  • Shows when a target area is visible

Cartographic functions:

• Distance calculation
  • Straight-line
  • Stream selection (arbitrary shape)
• Area calculation
• Range circles
• Bearing measurements
• Offset plotting (distance and bearing from a point)
• Datum shift: Calculates shift between Primary and Secondary datums for any point on map.
• Magnetic variation values: Calculates magnetic declination for any point
• UTM Grid / True north declination: Calculates variation between UTM grid and true north
• Horizontal earth curvature: Calculates true distance compensating for earth's curvature

• SPCS: Converts location to State Plane Coordinate System
•  

Tip: Many options leave drawing traces on DEMs and maps; to remove many of these, use the Force Redraw button. Overlays can be removed using the Overlay management functions.

Satellite image analysis:

• Automatically loads in multi-band Landsat, Quickbird and IKONOS imagery
• User-specificable band display (i.e choose which bands to display as Red, Green or Blue)
• Band histograms, scattergrams, ratios, differences
• Pre-defined normalized differential indices NDWI, NDVI, NDSI, NBR
• Digital filtering for sharpening, edge detection
• Satellite image component matrix and principal component calculation
• Imagery "training" for category classification
• Merging of 30m color data with 15m panchromatic imagery

(Above) For a location double-clicked on a DEM, the red curve shows the time for sunset; the green curve the time for sunrise, and the blue curve the duration of daylight.

Analyze menu:

• General coordinate converter (projection/datum)
• Sun/moon rise/set calculator
• Magnetic variation (both deviation and dip as function of position and altitude)

RasterGIS menu:

• Analyze DEM for holes
• Elevation frequency histogram
• Antenna heights

Database Menu:

• Allows loading of databases (shapefile, DBF, CSV) associated with loaded map. For shapefile DBF databases, you can plot the features based on database variables with a variety of symbols and colors, directly edit database entries, filter the database using standard queries and then create a subset shapefile of those filtered features.

Tip: While MicroDEM can handle raster files in UTM or geographic coordinates without intervention, it requires shapefiles and coordinate-related databases to be in geographic coordinates (latitude/longitude). The Data Manipulation section contains utilities to convert shapefiles from UTM to Lat/Lon and back again.

View Menu (used when DEM is loaded, with or without associated map):

• LOS: Calculates elevation profile and line-of-sight visibility (green for visible, red for not).
• Oblique: Creates a static oblique 3D view
• OpenGL: Creates a rotatable and modifiable 3D view
• Perspective: Creates a 3D landscape as viewed from a particular location (with the ability to drape photos or maps on top)
• Panorama: Similar to perspective, but creates 360-degree view
• Hint: If you have installed the Gazetteer data, you can use it to label peaks in the Panorama and Perspective views
• Circle Around: Creates an animation where you move around a point while constantly looking in the direction of the point.
• Fly Through / Live Flying: Creates a fly-through animation that can be saved as a movie. Fly Through follows a pre-determined route, while Live Flying allows you to control the flight with keyboard controls. VRML 3D Viewer (from toolbar): Allows creation of 3d VRML views

Right-click options (can be used on maps, photos and DEM views):

• Grid: Draws a UTM or lat/lon grid on map
• Load: Allows several options, including downloading of TerraServer map imagery for a particular location (DOQ or DRG); loading of catalogued DEM or DRG imagery that correlates with the currently displayed map; downloading of JPL TM imagery (432).
• Overlay: Allows overlay of US Census TIGER data or USGS Gazetteer info (if properly installed and indexed)
• Gazetteer: If installed, loads in full USGS Gazetteer database 3D Map Options: Sets parameters for 3D anaglyph display; also allows de-collaring of USGS 24K topo quads
• Download from USGS seamless server: Automatically creates DEM download links that work with USGS seamless server (seamless.usgs.gov)

GPS: Interfaces with GPS for real-time tracking, waypoint download/upload.

Data Manipulation: A separate section with many useful functions, including:

• Import, Export and Merging of a variety of types and formats of data Numerous shapefile/database utilities, including projection/datum conversions, adding field (including those from linked fields), merging shapefiles, etc.
• See a short tutorial on adding datum information to a GeoTiff file with MicroDEM.

Misc. Features:

Zip/unzip utilities

The ability to index map data (raster, TIGER, Gazetteer) for easy data index display and retrieval

Geo-referencing of scanned raster files

Basic shapefile creator and editor (points, lines and areas), but no advanced features such as snap, drill, etc.

Map annotation and marginalia tools, including many designed specifically for geology and oceanography applications

Perspective and panorama views can be produced in anaglyphic or side-by-side stereo views.

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