pyeo.coordinate_manipulation¶
Contains a set of functions for transforming spatial coordinates between projections and pixel indicies.
Unless otherwise stated, all functions assume that any geometry, rasters and shapefiles are using the same projection. If they are not, there may be unexpected errors.
Some of these functions call for an AOI shapefile. This is a single-layer shapefile containing only the geometry of one polygon.
These functions mainly work on the objects provided by the ogr and gdal libraries. If you wish to use them in your own
processing, a gdal.Image
object is usually the output from gdal.Open() and an ogr.Geometry object can be obtained from
a well-known text (wkt) string using the snippet object=ogr.ImportFromWkt("mywkt")
. For more information on wkt, see
https://en.wikipedia.org/wiki/Well-known_text_representation_of_geometry and the “QuickWKT” QGIS plugin.
Key functions¶
pixel_bounds_from_polygon()
Gets the indicies of the bounding box of a polygon within a raster
Function reference¶
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pyeo.coordinate_manipulation.
align_bounds_to_whole_number
(bounding_box)¶ Creates a new bounding box with it’s height and width rounded to the nearest whole number.
- Parameters
bounding_box (ogr.Geometry) – An ogr.Geometry object containing a raster’s bounding box as a polygon.
- Returns
bounds_poly – An ogr.Geometry object containing the aligned bounding box.
- Return type
ogr.Geometry
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pyeo.coordinate_manipulation.
check_overlap
(raster, aoi)¶ A test to see if a raster and an AOI overlap. :param raster: A gdal.Image object :type raster: gdal.Image :param aoi: A ogr.Dataset object containing a single polygon :type aoi: ogr.Dataset
- Returns
is_overlapped – True if the raster and the polygon overlap, otherwise False.
- Return type
bool
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pyeo.coordinate_manipulation.
floor_to_resolution
(input, resolution)¶ Returns input rounded DOWN to the nearest multiple of resolution. Used to prevent float errors on pixel boarders.
- Parameters
input (number) – The value to be rounded
resolution (number) – The resolution
- Returns
output – The largest value between input and 0 that is wholly divisible by resolution.
- Return type
number
Notes
Uses the following formula:
input-(input%resolution)
If resolution is less than 1, then this assumes that the projection is in decmial degrees and will be rounded to 6dp before flooring. However, it is not recommended to use this function in that situation.
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pyeo.coordinate_manipulation.
get_aoi_bounds
(aoi)¶ Returns a wkbPolygon geometry with the bounding rectangle of a single-layer shapefile
- Parameters
aoi (ogr.Dataset) – An ogr.Dataset object containing a single layer.
- Returns
bounds_poly – A polygon containing the bounding rectangle
- Return type
ogr.Geometry
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pyeo.coordinate_manipulation.
get_aoi_intersection
(raster, aoi)¶ Returns a wkbPolygon geometry with the intersection of a raster and a shpefile containing an area of interest
- Parameters
raster (gdal.Image) – A raster containing image data
aoi (ogr.DataSource) – A datasource with a single layer and feature
- Returns
intersection – An ogr.Geometry object containing a single polygon with the area of intersection
- Return type
ogr.Geometry
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pyeo.coordinate_manipulation.
get_aoi_size
(aoi)¶ Returns the width and height of the bounding box of an aoi.
- Parameters
aoi (ogr.Geometry) – A shapefile containing a single layer with a single polygon
- Returns
width, height – Width and height of the bounding box
- Return type
number
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pyeo.coordinate_manipulation.
get_combined_polygon
(rasters, geometry_mode='intersect')¶ Returns a polygon containing the combined boundary of each raster in rasters.
- Parameters
rasters (List of gdal.Image) – A list of raster objects opened with gdal.Open()
geometry_mode ({'intersect', 'union'}) – If ‘intersect’, returns the boundary of the area that all rasters cover. If ‘union’, returns the boundary of the area that any raster covers.
- Returns
combination – ogr.Geometry() containing a polygon.
- Return type
ogr.Geometry
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pyeo.coordinate_manipulation.
get_local_top_left
(raster1, raster2)¶ Gets the top-left corner of raster1 in the array of raster 2. Assumes both rasters are in the same projection and units.
- Parameters
raster1 (gdal.Image) – The raster to get the top-left corner of.
raster2 (gdal.Image) – The raster that raster1’s top-left corner is over.
- Returns
x_pixel, y_pixel – The indicies of the pixel of top-left corner of raster 1 in raster 2.
- Return type
int
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pyeo.coordinate_manipulation.
get_poly_bounding_rect
(poly)¶ Returns a polygon of the bounding rectangle of an input polygon. :param poly: An ogr.Geometry object containing a polygon :type poly: ogr.Geometry
- Returns
bounding_rect – An ogr.Geometry object with a four-point polygon representing the bounding rectangle.
- Return type
ogr.Geometry
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pyeo.coordinate_manipulation.
get_poly_intersection
(poly1, poly2)¶ A functional wrapper for ogr.Geometry.Intersection()
- Parameters
poly1 (ogr.Geometry) – The two geometries to intersect
poly2 (ogr.Geometry) – The two geometries to intersect
- Returns
intersection – A polygon of the intersection
- Return type
ogr.Geometry
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pyeo.coordinate_manipulation.
get_poly_size
(poly)¶ Returns the width and height of a bounding box of a polygon
- Parameters
poly (ogr.Geometry) – A ogr.Geometry object containing the polygon.
- Returns
width, height – Width and height of the polygon
- Return type
number
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pyeo.coordinate_manipulation.
get_raster_bounds
(raster)¶ Returns a wkbPolygon geometry with the bounding rectangle of a raster calculated from its geotransform.
- Parameters
raster (gdal.Image) – A gdal.Image object
- Returns
boundary – An ogr.Geometry object containing a single wkbPolygon with four points defining the bounding rectangle of the raster.
- Return type
ogr.Geometry
Notes
Bounding rectangle is obtained from raster.GetGeoTransform(), with the top left corners rounded down to the nearest multiple of of the resolution of the geotransform. This is to avoid rounding errors in reprojected geotransformations.
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pyeo.coordinate_manipulation.
get_raster_intersection
(raster1, raster2)¶ Returns a wkbPolygon geometry with the intersection of two raster bounding boxes.
- Parameters
raster1 (gdal.Image) – The gdal.Image
raster2 (gdal.Image) – The gdal.Image
- Returns
intersections – a ogr.Geometry object containing a single polygon
- Return type
ogr.Geometry
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pyeo.coordinate_manipulation.
get_raster_size
(raster)¶ Return the width and height of a raster, in that raster’s units.
- Parameters
raster (gdal.Image) – A gdal.Image object
- Returns
width, height – A tuple containing (width, height)
- Return type
number
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pyeo.coordinate_manipulation.
multiple_intersection
(polygons)¶ Takes a list of polygons and returns a geometry representing the intersection of all of them
- Parameters
polygons (list of ogr.Geometry) – A list of ogr.Geometry objects, each containing a single polygon.
- Returns
intersection – An ogr.Geometry object containing a single polygon
- Return type
ogr.Geometry
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pyeo.coordinate_manipulation.
multiple_union
(polygons)¶ Takes a list of polygons and returns a polygon of the union of their perimeter
- Parameters
polygons (list of ogr.Geometry) – A list of ogr.Geometry objects, each containing a single polygon.
- Returns
union – An ogr.Geometry object containing a single polygon
- Return type
ogr.Geometry
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pyeo.coordinate_manipulation.
pixel_bounds_from_polygon
(raster, polygon)¶ Returns the bounding box of the overlap between a raster and a polygon in the raster
- Parameters
raster (gdal.Image) – A gdal raster object
polygon (ogr.Geometry or str) – A ogr.Geometry object or wkt string containing a single polygon
- Returns
x_min, x_max, y_min, y_max – The bounding box in the pixels of the raster
- Return type
int
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pyeo.coordinate_manipulation.
pixel_to_point_coordinates
(pixel, GT)¶ Given a pixel and a geotransformation, returns the picaltion of that pixel’s top left corner in the projection used by the geotransform. NOTE: At present, this takes input in the form of y,x! This is opposite to the output of point_to_pixel_coordinates!
- Parameters
pixel (iterable) – A tuple (y, x) of the coordinates of the pixel
GT (iterable) – A six-element numpy array containing a geotransform
- Returns
Xgeo, Ygeo – The geographic coordinates of the top-left corner of the pixel.
- Return type
number
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pyeo.coordinate_manipulation.
point_to_pixel_coordinates
(raster, point, oob_fail=False)¶ - Returns a tuple (x_pixel, y_pixel) in a georaster raster corresponding to the geographic point in a projection.
Assumes raster is north-up non rotated.
- Parameters
raster (gdal.Image) – A gdal raster object
point (str, iterable or ogr.Geometry) –
- One of:
A well-known text string of a single point An iterable of the form (x,y) An ogr.Geometry object containing a single point
- Returns
- Return type
A tuple of (x_pixel, y_pixel), containing the indicies of the point in the raster.
Notes
The equation is a rearrangement of the section on affinine geotransform in http://www.gdal.org/gdal_datamodel.html
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pyeo.coordinate_manipulation.
reproject_geotransform
(in_gt, old_proj_wkt, new_proj_wkt)¶ Reprojects a geotransform from the old projection to a new projection. See [https://gdal.org/user/raster_data_model.html]
- Parameters
in_gt (array_like) – A six-element numpy array, usually an output from gdal_image.GetGeoTransform()
old_proj_wkt (str) – The projection of the old geotransform in well-known text.
new_proj_wkt (str) – The projection of the new geotrasform in well-known text.
- Returns
out_gt – The geotransform in the new projection
- Return type
array_like
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pyeo.coordinate_manipulation.
reproject_vector
(in_path, out_path, dest_srs)¶ Reprojects a vector file to a new SRS. Simple wrapper for ogr2ogr.
- Parameters
in_path (str) – Path to the vector file
out_path (str) – Path to output vector file
dest_srs (osr.SpatialReference or str) – The spatial reference system to reproject to
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pyeo.coordinate_manipulation.
write_geometry
(geometry, out_path, srs_id=4326)¶ Saves the geometry in an ogr.Geometry object to a shapefile.
- Parameters
geometry (ogr.Geometry) – An ogr.Geometry object
out_path (str) – The location to save the output shapefile
srs_id (int or str, optional) – The projection of the output shapefile. Can be an EPSG number or a WKT string.
Notes
The shapefile consists of one layer named ‘geometry’.