Question:
Can you help clarify my confusion about the Z factor? I am going through the Pit Fill/Hole Punch process, and I put in .18 since the training manual says 18cm and the raster is in meters. Is that correct?

Answer:
The z-factor you enter into the Pit Fill / Hole Punch process is the depth of a depression you want to fill prior to main terrain processing. The value given in the document refers to value that is tied to the overall error that the original lidar collect had as a value. In essence, it is saying, fill all the little depressions that are less than 18cm deep as they could be artifacts of the lidar interpolation process. If your DEM horizontal and vertical units are in meters, it would be correct to put in .18 as the maximum fill depth. If your vertical units are in feet or in centimeters, you would need to adjust that number based on the conversion factor. Here is some additional info on DEM preparation/z-factor for use with the ACPF:

• ArcGIS does not provide any way to see the elevation (z) units. That information is stored in the metadata from wherever you got the data from.
• You should definitely resample your DEM so that your x,y units are in WHOLE meters. If you have a 2 meter DEM, your x,y units should read 2,2. Floating point values like .9144 will slow things down tremendously and may cause problems.
• Do you know what coordinate system your DEM is in? We store all the ACPF data in UTM NAD 83, and all input files should be in the same coordinate system. If your DEM is not in UTM, I would suggest first projecting your raster to UTM, then resampling so that your x,y units are in WHOLE meters. Next I would figure out what my z-units are in currently, then convert them to centimeter integer (we recommend cm integer z-units for faster and more reliable processing). You can do this in raster calculator (i.e. if your z-units are currently in feet, you would take the whole raster times 30.48 to convert to cm integer). You would then have x,y units in whole meters and z units in cm. Your z-unit would then become .01.

Preparing your DEM and ensuring you understand what format it is in is perhaps the most critical part of the entire process. You want to make sure your data is in the correct format before you start running the tools. The zfactor forms the relationship between XY coordinates a Z value units. If your Z units and XY units are in meters, the Z factor = 1. If Z units are cm, the Zfactor is .01. The fill depth determines the depth of small depressions that are filled.