r.slope.aspect: add -c option

[paoloC]

Is it possible to add a '-c' option to r.slope.aspect in order to get an aspect raster map with compass notation (North=360, East=90, South=180, West=270) ? e.g.:

r.mapcalc "aspect_compass=if(isnull(aspect_from_east),null(), \
        if((aspect_from_east<90), 90-aspect_from_east, 360+90-aspect_from_east))"

[hamish]

it's pretty easy to do this by hand:

r.mapcalc "compass_aspect = 90 - theta_aspect"

and maybe a if(aspect < 0) {aspect = aspect + 360 } step after.

Hamish

[glynn]

Replying to paoloC:

Is it possible to add a '-c' option to r.slope.aspect in order to get an aspect raster map with compass notation (North=360, East=90, South=180, West=270) ? e.g.:

r.mapcalc "aspect_compass=if(isnull(aspect_from_east),null(), \
        if((aspect_from_east<90), 90-aspect_from_east, 360+90-aspect_from_east))"

Simpler version:

r.mapcalc "aspect_compass = (450 - aspect_from_east) % 360"

There's no need for an explicit null check, as almost any operation involving null returns null.

[hamish]

see code in addons/grass6/display/d.barb/main.c

    type_opt = G_define_option();
    type_opt->key = "aspect_type";
    type_opt->type = TYPE_STRING;
    type_opt->required = NO;
    type_opt->answer = "cartesian";
    type_opt->options = "cartesian,compass";
    type_opt->description = _("Direction map aspect type");

/* aspect flavours */
#define TYPE_GRASS 0
#define TYPE_COMPASS 1
...
    if (strcmp(type_opt->answer, "compass") == 0)
        aspect_type = TYPE_COMPASS;
    else
        aspect_type = TYPE_GRASS;
...
    angle = (aspect_type == TYPE_GRASS ? theta : 90 - theta);

Hamish

[martinl]

Milestone renamed

[neteler]

Ticket retargeted after milestone closed

[mmetz]

Implemented as new -n flag in r72229. The ticket can be closed when 7.6 is out.

[neteler]

Closing as added to ​https://trac.osgeo.org/grass/wiki/Release/7.6.0-News