This is PyTopo, an application for exploring tiled maps cached locally.

See the project home page at http://shallowsky.com/software/topo
for more information, examples, screenshots, hints on creating
custom maps, and more.

It can download data from OpenStreetMap or other map servers,
which may or may not require API keys; or you can use tiles from
commercial programs like the Topo! or tiles you've generated yourself.

It can also display GPX, KML or KMZ track logs, and can measure
distances and angles between points or give you the coordinates of
a point.

It uses PyGTK for its user interface, so you will need to PyGTK.
Linux users can get it through their distro, or by compiling from source;
Windows users can install it from pip. I don't have a good answer for
Mac users; possibly the easiest solution is to install GIMP (follow
the install links from https://gimp.org) then munge paths so that
other programs can find the PyGTK that comes with GIMP.

You can install it with pip install pytopo.
Or run it from the project directory by running pytopo/MapViewer.py
if you have the pytopo directory in your PYTHONPATH.
But if you want to see pin images, create a directory
/usr/share/pytopo and copy pytopo-pin.png into it.
Or just have pytopo-pin.png in the current directory when you run pytopo.

The first time you run it, pytopo will create a ~/.config/pytopo
directory for its configuration files, and a Maps directory for
map data.

pytopo -h gives usage examples.

If you need custom maps., edit ~/.config/pytopo/pytopo.sites to add new
map Collections (see examples in that file or on the project home page).

Code contributions appreciated!

Also in this project: ellie, a little script for reporting and plotting
statistics (distance and elevation change) read from a GPX track log.
More information: http://shallowsky.com/software/ellie/

Have fun!