Re: grdtrack (gmt5) - possible bug?

It is a geographic grid. the x/y locations are in lon/lat degrees.
grdinfo gives:
tomo_slice.grd: Title: Data gridded with continuous surface splines in
tension
tomo_slice.grd: Command:
tomo_slice.grd: Remark:
tomo_slice.grd: Gridline node registration used [Cartesian grid]
tomo_slice.grd: Grid file format: nf = GMT netCDF format (32-bit float),
COARDS, CF-1.5
tomo_slice.grd: x_min: -124.5 x_max: -104.5 x_inc: 0.05 name: x nx: 401
tomo_slice.grd: y_min: 27 y_max: 47 y_inc: 0.05 name: y ny: 401
tomo_slice.grd: z_min: -0.347601979971 z_max: 0.446707308292 name: z
tomo_slice.grd: scale_factor: 1 add_offset: 0
tomo_slice.grd: format: netCDF-4 chunk_size: 134,134 shuffle: on
deflation_level: 3

Why does it thinks it is a Cartesian grid?

When I add -fig it still outputs the distance in degrees, not in km.



On Thu, Mar 20, 2014 at 2:12 PM, Paul Wessel <[email protected]> wrote:

> Is your file a geographic grid? I.e., when you do grdinfo on it, does it
> say so?  If not then you will need to add -fg to force that.
> -p
>
> On Mar 20, 2014, at 10:54 AM, Shahar Barak <[email protected]> wrote:
>
>
> The manual says:
> "You may append +iinc*[**u*] to set the sampling interval (append
> appropriate unit); if not given then we default to half the minimum grid
> interval, and *if geographic we select great circle distances in km as
> the default unit and method*."
>
> However, when I run:
> gmt grdtrack -G${grd_file} -E${LON}/${LAT}+o${AZ}+l5
> I get:
> -118 33.5 -2.5 -0.0740850940347
> .
> .
> .
> -113 33.5 2.5 0.0141758602113
>
> So the distances are in degrees, not in km, as I understand from the
> manual. Why?
> Also, it seems like that one can only specify +l in degrees, and not in
> km. Why?
>
> I also tried specifying the units in km with +i :
> gmt grdtrack -G${grd_file} -E${LON}/${LAT}+o${AZ}+l5+i0.1k
>
> However, I get intervals of 0.1 degrees instead of 0.1 km:
> -118 33.5  -2.5 -0.0834747254848
> -117.9 33.5 -2.4 -0.0538280569017
> -117.8 33.5 -2.3 -0.0227038227022
> -117.7 33.5  -2.2 0.0134101686999
> -117.6 33.5 -2.1 0.0674700662494
> -117.5 33.5 -2 0.12702396512
>
> Is this a bug?
>
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>
>
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