Re: grdtrack (gmt5) - possible bug?

It works ok when I use endpoints instead of center and azimuth:
gmt grdtrack -G${grd_file} -E${LON1}/${LAT1}/${LON2}/${LAT2}+i10k -fg
-118 33.5 0 -0.0834747254848
-117.891972704 33.5016893489 10.0320097066 -0.0514965094364
-117.78393195 33.5032850827 20.0648907822 -0.0154709378555
-117.675878504 33.5047871606 30.0985935729 0.0234193657155
-117.567813133 33.5061955445 40.1330684004 0.0922054396147
-117.459736603 33.5075101984 50.1682655635 0.135183957513
-117.351649682 33.5087310886 60.2041353393 0.174436957097
-117.243553138 33.5098581842 70.2406279852 0.169260887889
-117.135447739 33.5108914563 80.2776937398 0.151650094147




On Thu, Mar 20, 2014 at 2:33 PM, Shahar Barak <[email protected]> wrote:

> 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?
>>
>> To unsubscribe, send the message "signoff gmt-help" to
>> [email protected]
>>
>>
>> To unsubscribe, send the message "signoff gmt-help" to
>> [email protected]
>
>
>

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