Re: grdtrack (gmt5) - possible bug?
Paul Wessel <[email protected]>
| Newsgroups | gmane.comp.gis.gmt.user |
|---|---|
| Message-ID | <[email protected]> |
On Mar 20, 2014, at 11:33 AM, Shahar Barak <[email protected]> wrote: > It is a geographic grid. the x/y locations are in lon/lat degrees. Well, it says the units are x, not degrees_east, etc. So no way to know. You probably gridded this file without -fg and hence it is necessarily labeled as Cartesian. When I use -fg it seems to understand +l50k. Without -fg it is Cartesian so +l5 is 5 units. The spacing seems right to me. -p > 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] > > To unsubscribe, send the message "signoff gmt-help" to [email protected] To unsubscribe, send the message "signoff gmt-help" to [email protected]