topic Re: DEM floating point -> Integer and prj.adf modification problem in Water Resources Questions

DEM floating point -> Integer and prj.adf modification problem

TomaszBartus — Fri, 05 Apr 2013 09:22:04 GMT

I have DEM data in floating point format. Data are in meter unit with two significant digits after dot (e.g. 418.34 m above sea level). I have to convert the floating point DEM into integer DEM before terrain Arc Hydro Tools preprocessing.

Procedure:

1. Raw data DEM file: DEM
2. The raster calculator -> CMT_cm: CMT*100
3. The raster calculator -> CMT_cm_int: INT("CMT_cm")
4. the prj.adf file edition to set the ZUnits to 100.

Units METERS
NO Zunits

change to:
Units METERS
Zunits 100

Well, now the problem:

after making changes in the prj.adf file and after adding the grid to the stage, the file is modified again by the system to the "Zunits NO" value. File modification took place with closed ArcGIS applications, and was added to a empty stage.
What am I doing wrong?

help 😉

Re: DEM floating point -> Integer and prj.adf modification problem

MarkBoucher — Fri, 05 Apr 2013 15:25:33 GMT

Arc Hydro process my floating point DEM just fine and has for years. Why are you converting it to integer?

Mark
Arc Hydro Problem Solvers Thread

Re: DEM floating point -> Integer and prj.adf modification problem

TomaszBartus — Sat, 06 Apr 2013 05:34:51 GMT

I read in tutorials, that the functions associated with the sinks recognition requires the conversion. If not, it will be nice. But to know, what I did wrong?

Re: DEM floating point -> Integer and prj.adf modification problem

MarkBoucher — Mon, 08 Apr 2013 14:19:39 GMT

Tomasz,

Have you had trouble making the Arc Hydro functions work with the floating point DEM?

As for the Sink functions:

Sink Evaluation help says the input DEM being evaluated for sinks should have linear and z units explicitly set. If the z unit is not set, the tool will assumes that the z-unit is the same as the linear unit.

It does not seem to me that it would require any changes to the DEM if the DEM raster has the same units in horizontal and vertical directions. Basically, the assumption is the z-unit has the same units as the x, y unless the data indicates otherwise.

Sink Pre Screening help does not mention anything about the z-unit

Sink Selection does not require the DEM.

Sink Watershed Delineation does not require the DEM.

If you can explain what you are trying to do with the sinks and the sink functions or share your data, maybe I can help you more.

If I were you, I'd try to run the processes with the DEM you have. The problems you have, if nay, may not be related to the z-unit or the integer/floating point issues.