ascgrid.zip

ESRI ASCII grid read/write

MATLAB ASCII Grid Interface
===========================
This project includes tools to simplify handling ASCII raster data in
MATLAB. The *Mapping Toolbox* contains an `arcgridread` function, but it
doesn't implement the entire ESRI ASCII grid format, and there is no
equivalent `arcgridwrite`.
Getting started
---------------

The code in this package revolves around the *ascgrid* class. The
easiest way to get started is to run

asc = ascgrid(fnm);

where `fnm` is a path to an existing ESRI ASCII grid file (*\*.asc*). An
*ascgrid* can also be created from scratch by supplying a data matrix
`Z` and a header struct `hdr`:

asc = ascgrid(Z, hdr);

Working with ascgrid objects
----------------------------

The resulting object `asc` can be added, subtracted, multiplied,
divided, or compared with other instances of the *ascgrid* class. For
example, a glacier hydraulic potential surface could be calculated from
surface (`sur`) and ice thickness (`thickness`) *ascgrid* objects as:

rho_w = 1000;
rho_i = 910;
g = 9.8;
bed = sur - thickness;
pot = rho_w * g * bed + rho_i * g * thickness;

The resulting dataset `pot` is a new *ascgrid* instance with proper
spatial reference information, and can be exported to a file `fnm` with:

tofile(pot, fnm);

Furthermore, each *ascgrid* instance has a number of methods (functions)
that work on it to retrieve data, perform analyses, or resize or sample
the raster while preserving correct header information. For example, to
calculate hillslope:

m = slope(asc);

At the time of writing, the following methods exist:

Method Description
------------------------------------------- ------------------------------------------------
`checkheader(asc)` Validate header information
`getheader(asc)` Retrieve header as a `struct`
`asmatrix(asc)` Output raster data as a matrix
`coordmesh(asc)` Generate coordinate matrices
`size(asc)` Return raster dimensions
`min(asc)`, `max(asc)`, `minmax(asc)` Return values at extrema
`getregion(asc)` Return the data bounding coordinates
`getindices(asc, x, y)` Return the indices nearest an (x,y) coordinate
`sample(asc, x, y)` Return data value at an (x,y) coordinate
`clip(asc, minval, maxval)` Limit data to a `minval`/`maxval`
`resample(asc, res)` Resample grid to new resolution
`resize(asc, limits)` Resize grid to new spatial limits
`slope(asc)` Return the slope
`gradient(asc)` Return a gradient vector field
`aspect(asc)` Return slope aspect
`upstream(asc)` Return upstream area
`contour(asc, ...)`, `contourf(asc, ...)` Create controur plots customized for *ascgrid*
`surf(asc, ...)` Create surface plots customized for *ascgrid*
`pcolor(asc, ...)` Create pcolor plots customized for *ascgrid*
`imshow(asc, ...)` Create imshow plots customized for *ascgrid*
`tofile(asc, fnm)` Export data to a valid ESRI ASCII grid file

Development
-----------

https://bitbucket.org/njwilson23/ascgrid