Major and minor graticule for maps?

Question

I have created the following map, which has a uniform gray grid with 1° intervals both for meridians and parallels:

I would also like to have the meridians and parallels thicker and in black for every 5° interval (while keeping the 1° grid), so that gridlines match the latitude and longitude labels as shown below:

I know that MATLAB has major and minor grids for standard 2D plots, and I have used them in the past. However, as far as I know, maps don't have this feature.

I think that what I want to do can be achieved by accessing the map object properties (using gcm or getm) and specifying a black color property to the specific subset of meridians and parallels (using setm). Maybe the functions gridm or axesm can handle this, but I'm not sure.

In practice, I don't know how to do this as I haven't got any experience with maps. I would really appreciate a helping hand.

Code:

Note: This code requires the Mapping Toolbox.

% Read vector features and attributes from shapefile.
landareas = shaperead('landareas.shp', 'UseGeoCoords', true);

% Define map axes and set map properties.
axesm ('lambert',...
    'MapLonLimit', [-70 10],...
    'MapLatLimit', [30 70],...
    'MapParallels', [38.00555556 71.01111111],...
    'Frame', 'on',...
    'FLineWidth', 1,...
    'Grid', 'on',...
    'GLineStyle', '-',...
    'GLineWidth', 0.1,...
    'GColor', [.7 .7 .7]);

% Display map latitude and longitude data.
geoshow(landareas, 'FaceColor', [1 1 .5], 'EdgeColor', [.3 .3 .3]);

% Toggle and control display of graticule lines.
gridm('MLineLocation', 1,...
    'MLabelLocation', 5,...
    'PLineLocation', 1,...
    'PLabelLocation', 5);

% Toggle and control display of meridian labels.
mlabel on;

% Toggle and control display of parallel labels.
plabel on;

axis off;

Answer 1

Here is a quite simple trick: Make a second axes in the same 'Position' and make your desired major grids there.

Starting from your code with some modifications (I combined axesm and gridm):

landareas = shaperead('landareas.shp', 'UseGeoCoords', true);

% make the first axes and get the handle of it
ha = axes;

axesm ('lambert',...
    'MapLonLimit', [-70 10],...
    'MapLatLimit', [30 70],...
    'MapParallels', [38.00555556 71.01111111],...
    'Grid', 'on',...
    'GLineStyle', '-',...
    'GLineWidth', 0.1,...
    'GColor', [.7 .7 .7], ...
    'MLineLocation', 1,...
    'PLineLocation', 1);

geoshow(landareas, 'FaceColor', [1 1 .5], 'EdgeColor', [.3 .3 .3]);

axis off;

And then making the second axes:

% get the position of the first axes
L = get(ha, 'Position');

% make a new axes in the same position
axes('Position', L)

axesm ('lambert',...
    'MapLonLimit', [-70 10],...
    'MapLatLimit', [30 70],...
    'MapParallels', [38.00555556 71.01111111],...
    'Frame', 'on',...
    'FLineWidth', 2,...
    'Grid', 'on',...
    'GLineStyle', '-',...
    'GLineWidth', 2,...
    'GColor', [.2 .2 .2], ...
    'MLineLocation', 5,...
    'MLabelLocation', 5,...
    'PLineLocation', 5,...
    'PLabelLocation', 5);

mlabel on;
plabel on;
axis off;

You will get this result:

It is not even necessary to get and set the positions, since they both will be created in the default position.