Profile files have 6 columns:

• distance downstream (meters)
• elevation (after fixing)
• raw elevation
• contributing area (number of cells)
• X
• Y

The proffix2.aml profile-tracing algorithm

• Geographic projections are not equidistant, but they will will lose information if converted to equidistant projection.

  This macro can work on a geographic projection, using different distance values for vertical, horizontal, and diagonal lines.

• Profiles through DEMs (at least in the ARC/INFO environment) yield a bilinear interpolation of the four lattice points nearest to the sample points. Therefore river profiles include points partway up the river banks.

  This macro steps (slowly) from lattice point to lattice point, always getting the lowest elevation of the represented stream bed.

• DEMs frequently contain "sinks" from which water cannot flow. These are usually artifacts. Depending on the algorithm used in DEM creation, the low values tend to be correct, while the high values that block flow are the result of narrow channels "falling through the cracks" of a coarse DEM. The usual solution is to flag the real sinks, then fill the rest. Flowidrection, flowaccumulation, and other functions are performed on the filled DEM.

  This macro outputs the elevation of the raw DEM.

• Most algorithms trace flowdirection across a filled sink, ignoring the information below.

  Proffix2.aml,when it encounters a filled sink, will interrogate the raw DEM and trace the path of steepest descent. When it reaches a low point, it assigns weights to paths of shallowest ascent and to the direct path to to sink's pour point, and works its way uphill to that pour point.

• Any profile containing raw elevations will have uphill segments at sinks.

  When proffix2.aml reaches an uphill part of the profile, it will assign a user-designated minimum slope to the river. Both raw and fixed profiles are output. Also, the altered values are saved to a different files so that they can be used to alter the DEM itself.