Using 3dMapper for Idaho Soil Survey Analysis - Page 2

Adding Aspect Classes

First, click on the Aspect option under Coverages.  Then click the Apply button and the aspect classes will draw on the Local View.

Flat slopes (below 1%) are drawn in black, and are not considered to possess an aspect.  For other slopes aspect is expressed as an angle in degrees, measured clockwise from north.  Azimuths are drawn using a continuous color gamut ranging from blue (north) to red (south) and back to blue.  Think of it as a sort of temperature map, with the north slopes cooler (blue) and the south slopes warmer (red).

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Looking at Landscape Curvature

Two different types of curvature can be displayed:

Profile Curvature - perpendicular to the contours
Planar Curvature - parallel to the contours

Both of these are found under Coverages on the main menu screen.

Profile Curvature

This is landform curvature measured "downhill", perpendicular to the contours. Straight slopes are colored white. Shades of red are used for convex slopes (as encountered when traversing a ridge). Blue is used for concave slopes.  End points on the color spectrum are determined by adjustable curvature limits.  Numerically, profile curvature is the rate of change of slope per unit distance.   In other words, as you walk downhill, does the slope increase or decrease, and how rapidly is it changing?  3dMapper displays curvature values in % per 100 feet, or % per 100 meters, depending on the units of the DEM.

Planar Curvature

This is landform curvature measured along the contours. Shades of yellow are used for convex slopes (hills, ridges), whereas shades of green are used for concave slopes (depressions, valleys). Endpoints on the color spectrum are determined by adjustable curvature limits.

Curvature Limits

Changing curvature limits is similar to setting a slope neighborhood.  Use them to determine the smallest area for which curvature will be determined.  Change the values under Options / Curvature Limits.

Curvatures are depicted using a range of colors ending in a fully saturated hue (e.g., pure red). The curvature limit determines the curvature value associated with that color.  All curvatures greater than the limit (in absolute value) are drawn in the same color. Large absolute curvatures are associated with small features, thus this option in effect determines the smallest feature whose curvature is of interest.  (All smaller features are drawn with the same color, so you can't tell them apart from one another.)  To set the curvature limit, enter a radius of curvature (in meters or feet, depending on the grid units).  The default value is 100 meters.

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Adding Existing Digital Soil Lines

Assuming the data was prepared and projected propoerly as described above, add soil lines using the File / Import Ascii / Arc Coverage commands.

Select the appropriate ASCII soil line coverage with the ".arc" extension.

Give it an appropriate name.

Then check the box next to it in the list of Coverages then click the Apply button..

This is an example of an overlay of soil lines onto the 3dMapper image.  Line colors and line widths can be set in Options / Settings on the main menu.

Remember, the soil lines appear but the attributes of the soil polygons do not.  This is just a visual reference.

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Data at the Cursor Location

Any time the cursor is placed over part of the image on the Local Display, coordinate information is displayed at the bottom of the main menu screen.  For example, on the screen below, the position of the local view cursor shows the x and y coordinates (in the projection native to ASCII files that were imported), the z or elevation value (in the units set for the imported data), the slope (in percent), the aspect (in compass and degrees), and both the planar and profile curvature values.

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Plotting a Transect

Select Plot Transect under the Local View menu section.  Place the cursor on the Local View and left click to start the transect.  Continue left clicking until all points along the transect have been identified.  After the last transect point has been entered, right click to show the transect graph.

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Adding Contour Lines

Adding contour lines can help define landscape characteristics.  Use the Contour Interval option on the 3dMapper main menu to set the contour interval.  Changing the contour interval simply redraws the screen.

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Printing Maps

There is no "Print" function associated with the 3dMapper program.  In order to capture a screen image for printing, either use a screen capture program or use the following keystrokes:

Shift-Print Screen:  Captures the entire screen and places it in the clipboard
Alt-Print Screen:  Captures the active window and places it in the clipboard

Then Paste the clipboard into your application (Word, Excel, etc.)

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Other Features

It is possible to add lines, by screen digitizing points (individual mouse clicks) or by stream digitizing (holding down the left mouse button and dragging the cursor).
It is possible to add other raster data layers, such as satellite imagery, to the Coverages list.
 

It is possible to add labels to the data on the screen.

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