anuga.Geo_reference

class anuga.Geo_reference(zone=None, xllcorner=0.0, yllcorner=0.0, datum='wgs84', projection='UTM', units='m', false_easting=None, false_northing=None, hemisphere='undefined', epsg=None, NetCDFObject=None, ASCIIFile=None, read_title=None)

Bases: object

Coordinate reference system for an ANUGA domain.

Variables:

• zone (int) – UTM zone (1–60), or -1 (DEFAULT_ZONE) for non-UTM / arbitrary origin (e.g. a wave-tank simulation).

• hemisphere (str) – 'southern', 'northern', or 'undefined'.

• xllcorner (float) – X coordinate (easting) of the local origin relative to the UTM grid.

• yllcorner (float) – Y coordinate (northing) of the local origin relative to the UTM grid.

• datum (str) – Geodetic datum (default 'wgs84').

• projection (str) – Map projection (default 'UTM').

• units (str) – Units of measurement (default 'm').

• false_easting (int) – False easting offset (500 000 m for WGS84 UTM).

• false_northing (int) – False northing offset (10 000 000 m southern, 0 m northern).

• epsg (int or None) – EPSG code for the coordinate reference system. For WGS84 UTM this is auto-computed from zone and hemisphere (32600 + zone for northern, 32700 + zone for southern). Returns None when the zone is DEFAULT_ZONE or the CRS cannot be determined.

__init__(zone=None, xllcorner=0.0, yllcorner=0.0, datum='wgs84', projection='UTM', units='m', false_easting=None, false_northing=None, hemisphere='undefined', epsg=None, NetCDFObject=None, ASCIIFile=None, read_title=None)

Parameters:

• zone (int, optional) – UTM zone (1–60) or -1 for no UTM framework. Inferred from epsg when possible if not supplied.

• xllcorner (float, optional) – X (easting) of the local origin in metres.

• yllcorner (float, optional) – Y (northing) of the local origin in metres.

• datum (str, optional) – Geodetic datum. Default 'wgs84'.

• projection (str, optional) – Map projection. Default 'UTM'.

• units (str, optional) – Distance units. Default 'm'.

• false_easting (int, optional) – Override the default false easting for the hemisphere.

• false_northing (int, optional) – Override the default false northing for the hemisphere.

• hemisphere (str, optional) – 'southern', 'northern', or 'undefined'. Inferred from epsg when possible if not supplied.

• epsg (int, optional) – EPSG code. For WGS84 UTM codes (32601–32660 northern, 32701–32760 southern), zone and hemisphere are inferred automatically when they have not been set explicitly.

• NetCDFObject (file handle, optional) – Open NetCDF file to read geo-reference attributes from.

• ASCIIFile (file handle, optional) – Open text file to read geo-reference attributes from.

• read_title (str, optional) – Title line already read from ASCIIFile (pass if the caller has already consumed it).

Methods

__init__([zone, xllcorner, yllcorner, ...])
change_points_geo_ref(points[, points_geo_ref])	Change points to be absolute wrt new georef 'points_geo_ref'.
get_absolute(points)	Given a set of points geo referenced to this instance, return the points as absolute values.
get_epsg()	Return the EPSG code for this coordinate reference system.
get_hemisphere()	Check if this georef has a defined hemisphere.
get_origin()	Get origin of this geo_reference.
get_relative(points)	Convert points to relative measurement.
get_xllcorner()	Get the X coordinate of the origin of this georef.
get_yllcorner()	Get the Y coordinate of the origin of this georef.
get_zone()	Get the zone of this georef.
is_absolute()	Test if points in georef are absolute.
is_located()	Return True if this geo-reference describes a real, located CRS.
read_ASCII(fd[, read_title])	Set georef attribtes from open text file.
read_NetCDF(infile)	Set georef attributes from open NetCDF file.
reconcile_zones(other)
set_false_easting_northing([false_easting, ...])
set_hemisphere(hemisphere)
set_zone(zone)	Set zone as an integer in [1,60] or -1 (DEFAULT_ZONE = unlocated).
write_ASCII(fd)	Write georef attriutes to an open text file.
write_NetCDF(outfile)	Write georef attributes to an open NetCDF file.

Attributes

epsg	EPSG code for this coordinate reference system.

change_points_geo_ref(points, points_geo_ref=None)

Change points to be absolute wrt new georef ‘points_geo_ref’.

points the points to change points_geo_ref the new georef to make points absolute wrt

Returns the changed points data. If the points do not have a georef, assume ‘absolute’ values.

property epsg

EPSG code for this coordinate reference system.

For WGS84 UTM projections the code is computed automatically from zone and hemisphere when it has not been set explicitly:

• Northern hemisphere: 32600 + zone (e.g. zone 55N → EPSG 32655)

• Southern hemisphere: 32700 + zone (e.g. zone 55S → EPSG 32755)

Returns None when the zone is DEFAULT_ZONE (-1) or the CRS cannot be determined.

Return type:

int or None

get_absolute(points)

Given a set of points geo referenced to this instance, return the points as absolute values.

get_epsg()

Return the EPSG code for this coordinate reference system.

Returns:

EPSG code, or None if unknown.

Return type:

int or None

get_hemisphere()

Check if this georef has a defined hemisphere.

get_origin()

Get origin of this geo_reference.

get_relative(points)

Convert points to relative measurement.

points Points to convert to relative measurements

Returns a set of points relative to the geo_reference instance.

This is the inverse of get_absolute().

get_xllcorner()

Get the X coordinate of the origin of this georef.

get_yllcorner()

Get the Y coordinate of the origin of this georef.

get_zone()

Get the zone of this georef.

is_absolute()

Test if points in georef are absolute.

Return True if xllcorner==yllcorner==0 indicating that points in question are absolute.

is_located()

Return True if this geo-reference describes a real, located CRS.

A geo-reference is located when either:

• zone is a valid UTM zone (1–60), or

• an EPSG code has been set (covers national grids, geographic CRS, and any other projected CRS that does not use UTM zones, e.g. EPSG:28992 Netherlands RD New, EPSG:27700 British National Grid).

A geo-reference with zone == DEFAULT_ZONE (-1) and no EPSG code is unlocated — this is the case for wavetank or other hypothetical simulations with an arbitrary local origin.

Return type:

bool

read_ASCII(fd, read_title=None)

Set georef attribtes from open text file.

fd handle to open text file

read_NetCDF(infile)

Set georef attributes from open NetCDF file.

Parameters:

infile (file handle) – Handle to an open NetCDF file.

set_zone(zone)

Set zone as an integer in [1,60] or -1 (DEFAULT_ZONE = unlocated).

A negative zone in [-60, -2] is interpreted as a southern hemisphere shorthand: the zone number is taken as abs(zone) and hemisphere is set to ‘southern’ when it is currently ‘undefined’.

Note: zone=-1 is reserved for DEFAULT_ZONE (unlocated simulation) and is NOT interpreted as zone 1 southern hemisphere. For zone 1 south, pass zone=1 with hemisphere=’southern’ explicitly.

write_ASCII(fd)

Write georef attriutes to an open text file.

fd handle to open text file

write_NetCDF(outfile)

Write georef attributes to an open NetCDF file.

Parameters:

outfile (file handle) – Handle to an open NetCDF file.