##Introduction

The nctoolbox has a set of functions that can be useful as basic matlab style functions to deal with different aspects of dealing with geospatial data.

These functions include (in no particular order):

• interptime
  • Function to interpolate an up to order 4 data matrix (including time) to a specific time or resample to an array of times.

Like this:

>> data = interptime(data, datatime, [2005 1 1 0 0 0]);

• zsliceg
  • Horizontal slice at a fixed vertical level.

Like this:

>> varz=zsliceg(data,z,depth);

• getinterp
  • This provides the matlab interpolant for interpolation of an input data matrix.

Like this:

>> int = getinterp(data, lon, lat, method);

• interptoxy
  • Interpolates a rank 2 or 3 data matrix to an xy point or array of points. (Matrices that are rank 3 return a profile at the point.)

Like this:

>> data = interptoxy(data, datalon, datalat, -77, 45, 'linear');

• vsliceg
  • Vertical slice along a line of xy coordinates.

Like this:

>> [X,Z,VDATA] = vsliceg(DATA,GRD,CX,CY);

• nc_genslice
  • Takes a vertical slice along xy and time for comparing trajectories (like glider passes) to model data.

Like this:

[Tvar,Tdis,Tzed,Tlon,Tlat] = nc_genslice(file,varname,lonTrk,latTrk,timTrk)

Basically works like GSLICE. Get a "generic" vertical slice out of ROMS output file at coordinates specified by a vector of lon, lat and time (e.g. a ship transect or a glider track)

Input: file netcdf or opendap url (aggregation across time) varname name of the variable we want along the track lon, lat coordinates along the track timTrk time values along the track given as Matlab datenum Must have the same dimension as lon/lat OR be a scalar in which case it is assumed the track is for a single time Output: Tvar interpolated 2D data along the track Tdis 2D range or distance along the track (in kilometers) Tzed 2D depth along the track Tlon 2D lon along the track Tlat 2D lat along the track

gslice originally by John Evans modified by Weifeng Gordon Zhang This version by John Wilkin 2011-01-26 Alexander Crosby 2011 April - Update to using new toolbox

• ncunits
  • Very useful function for converting a data matrix from a set of known units to another set of units (specified as strings).

Like this:

>> converted_data = ncunits(data, 'm/s', 'cm/s');

• ModelLook
  • This is a frame work for easy model visualization and exploration. It is mostly point and click and provides a few different ways for understanding 2-, 3-, and 4-d variables from CF compliant netcdf files. At the moment this only works for regularly gridded model data, but it will be available for use with unstructured grid use as well, soon. It is called with the openDap link as the first argument and the matlab datevec or datenum for the time you want to look at (finds the nearest time in model).
  • For 3-d and 4-d gridded variables, the layer at index 1 is plotted. Sometime this does not correspond to the the surface layer of a model, which is the case with the example below.

Like this:

>> modellook('uri','http://testbedapps.sura.org/thredds/dodsC/estuarine_hypoxia/ch3d/agg.nc','date', [2004 1 10 21 0 0],'level', 1);

[http://nctoolbox.googlecode.com/hg/cdm/utilities/modellook.PNG?r=c1f2425a8006f3c5c92174a14cb4aac9dd3aae95]