show

Display 2-D occupancy map

Syntax

show(map)

show(map,'local')

show(map,'grid')

show(___,Name,Value)

mapImage = show(___)

Description

show(map) displays the occupancy grid map in the current axes, with the axes labels representing the world coordinates.

show(map,'local') displays the occupancy grid map in the current axes, with the axes labels representing the local coordinates instead of world coordinates.

show(map,'grid') displays the occupancy grid map in the current axes, with the axes labels representing the grid coordinates.

show(___,Name,Value) specifies additional options specified by one or more name-value pair arguments.

mapImage = show(___) returns the handle to the image object created by show.

Examples

Create and Modify Occupancy Map

Create an empty map of 10-by-10 meters in size.

map = occupancyMap(10,10,10);

Update the occupancy of specific world locations with new probability values and display the map.

x = [1.2; 2.3; 3.4; 4.5; 5.6];
y = [5.0; 4.0; 3.0; 2.0; 1.0];

pvalues = [0.2; 0.4; 0.6; 0.8; 1];

updateOccupancy(map,[x y],pvalues)
figure
show(map)

Inflate the occupied areas by a radius of 0.5 m. The larger occupancy values overwrite the smaller values.

inflate(map,0.5)
figure
show(map)

Get the grid locations from the world locations.

ij = world2grid(map,[x y]);

Set occupancy values for the grid locations.

setOccupancy(map,ij,ones(5,1),'grid')
figure
show(map)

Convert PGM Image to Map

Convert a portable graymap (PGM) file containing a ROS map into an occupancyMap for use in MATLAB.

Import the image using imread. Crop the image to the playpen area.

image = imread('playpen_map.pgm');
imageCropped = image(750:1250,750:1250);
imshow(imageCropped)

PGM values are expressed from 0 to 255 as uint8. Normalize these values by converting the cropped image to double and dividing each cell by 255. This image shows obstacles as values close to 0. Subtract the normalized image from 1 to get occupancy values with 1 representing occupied space.

imageNorm = double(imageCropped)/255;
imageOccupancy = 1 - imageNorm;

Create the occupancyMap object using an adjusted map image. The imported map resolution is 20 cells per meter.

map = occupancyMap(imageOccupancy,20);
show(map)

Input Arguments

map — Map representation

occupancyMap object

Map representation, specified as a occupancyMap object. This object represents the environment of the vehicle. The object contains a matrix grid with values representing the probability of the occupancy of that cell. Values close to 1 represent a high probability that the cell contains an obstacle. Values close to 0 represent a high probability that the cell is not occupied and obstacle free.

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: 'Parent',axHandle

Parent — Axes to plot the map

Axes object | UIAxes object

Axes to plot the map specified as either an Axes or UIAxes object. See axes or uiaxes.

FastUpdate — Update existing map plot

0 (default) | 1

Update existing map plot, specified as 0 or 1. If you previously plotted your map on your figure, set to 1 for a faster update to the figure. This is useful for updating the figure in a loop for fast animations.

Outputs

mapImage — Map image

object handle

Map image, specified as an object handle.

Version History

Introduced in R2019b