How to wrap axes using geoplot

I'm trying to plot a polygon from an exported ArcGIS shapefile that represents the geologic units on Mars. I've loaded the dataset into MATLAB using readgeoraster() and then plotted them using geoplot(). The polygon I'm interested in straddles the Martian meridian line, but when I shift the map over so it's centered on this polygon, the half on the eastern side of the meridian is missing (see image). I'd like to know how I can wrap the data and geoplot axes around the meridian line (so that the Longitude axis goes from 175 E, 180 E to 5 W, 10 W, and so on). My current code is below.

Thanks!

figure(1)
geoplot(map)
geobasemap('none')
geolimits([-15 5], [175 180])

Answer 1

[Umar]

Hi @Sabrina Khan,

I read your comments. To resolve the issue of visualizing a polygon that straddles the Martian meridian in MATLAB, you will need to modify your longitude values to properly wrap around from 175°E through 180° to 5°W. This involves adjusting the data such that when you plot, it creates a seamless transition across the -180°/180° boundary. First, you will need to manipulate your longitude data. For longitudes greater than 180°, subtract 360° from them. This ensures that all longitudes are expressed in the range of -180° to 180°. When setting your geographic limits using geolimits, you should specify limits that encompass both ends of your desired range (e.g., from -175° to 10°). Here is a sample code snippet that illustrates these steps.

% Load your shapefile data (assuming 'lat' and 'lon' variables)
% lat = ...; % Latitude values from shapefile
% lon = ...; % Longitude values from shapefile

% Adjust longitude for wrapping
lon(lon > 180) = lon(lon > 180) - 360;

% Create a figure for plotting
figure(1);
geoplot(lat, lon, 'b-'); % Use blue line style for plotting
geobasemap('none');

% Set geographic limits to wrap around the meridian
geolimits([-15 5], [-175 10]); % Adjust as needed based on your data

% Optionally add titles or labels
title('Geologic Units on Mars');
xlabel('Longitude');
ylabel('Latitude');

Before plotting, ensure that your latitude and longitude arrays match in size and format. Mismatched arrays can lead to errors or unintended behavior in plotting functions. If you continue experiencing issues with visualizing complex shapes or large datasets, consider using additional MATLAB functions such as geoscatter for point data or geobubble for bubble charts, which may provide clearer insights into your geological features.

Depending on your analysis needs, explore different basemaps available in MATLAB. While none is useful for custom plots, using a topographic or terrain basemap might enhance interpretability if geographical context is important.

By applying these adjustments and considerations, you should be able to effectively visualize your polygon across the Martian meridian without missing portions of your data.

If further issues arise, please feel free to share more details about any specific errors or behaviors encountered during execution.

Hope this helps.