[GRASS-user] East/West Horizons Giving Negative Numbers

Ashley Cale ashleycale1 at gmail.com
Wed May 20 17:57:00 PDT 2020


Hello Everyone!

I'm a grad student who is relatively new to GrassGIS and I was wondering if
someone here can help me figure out what's wrong with my east and west
horizon calculations?

I am trying to compute my east and west horizon angle from my DEM using the
command r.horizon. My output raster contains negative numbers and it's my
understanding that the range of output values should be between 0 and 360.
I used -d to make sure that my output is in degrees rather than radians.

Can anyone help me solve this problem? Or point me in the right direction?

Thank you for the help!
Ashley

Here is the r.info output from my generated east horizon raster.
 |----------------------------------------------------------------------------|
 |                                      |
 |  Type of Map: raster        Number of Categories: 0        |
 |  Data Type:  FCELL                           |
 |  Data Units:  degrees       Vertical datum: (none)        |
 |  Rows:     7532                            |
 |  Columns:   5860                            |
 |  Total Cells: 44137520                          |
 |    Projection: UTM (zone 10)                      |
 |      N: 4543151.24515692  S: 4317194.98362237  Res: 29.99950366  |
 |      E: 759846.34683197  W: 584057.70444841  Res: 29.99806184   |
 |  Range of data:  min = -90 max = 78.47394               |
 |                                      |
 |  Data Description:                            |
 |  generated by r.horizon                         |
 |                                      |
 |  Comments:                                |
 |  r.horizon -d elevation="dem30m at PERMANENT" direction=0 start=0.0 end=\  |
 |  360.0 output="east" distance=1.0 file="-"                |
 |                                      |
 |  Horizon view from azimuth angle 0.00 degrees CCW from East       |
 |                                      |
 +----------------------------------------------------------------------------+
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