[Summary]
This application can view map of the Geospatial Information Authority of Japan or OpenTopoMap with iPhone, iPad and Apple Watch.
And, show your current location at the map.
OpenTopoMap maps show the whole world. The Geospatial Information Authority maps show Japan and its surroundings.

GPS track of GPX file can be displayed on the map.

You can view the the latitude / longitude, altitude / barometric pressure of your location.

You can display the compass on the map and rotate the map according to the current direction. (Compass compatible models only)

Since the topographic map data is cached on the terminal, it can be viewed offline.

[Method of operation]
Single tap :
Displays the latitude / longitude, altitude / pressure of the current location, and map direction.
Double tap :
Zoom and display the map.
Drag up, down, left and right :
Scroll up, down, left, and right to display the map.
Press and hold the screen :
Display detailed menu.
Turn the digital crown :
Rotate and display the map.

*To display GPS tracks on a map, you need to have a GPX file sent to your iPhone, iPad and Apple Watch.

[Notes]
The topographic map data of this application uses data provided by the Geospatial Information Authority of Japan and OpenTopoMap website.

Please note that the cached topographic map data may be deleted due to app updates or lack of free space on OS.

This application uses the position information of GPS and displays current location. Please understand that it may not be possible to display the correct location in places where GPS radio waves are difficult to enter, such as indoors or near high buildings. If the accuracy of the position information is poor, the mark of the present location will be displayed larger.

The altitude and barometric pressure display the value of iPhone, iPad and Apple Watch sensor, not sea level rehabilitation.

The direction of the map indicates true north. Compass display can only be displayed on compass-compatible models.

The position information may be used while using this application, which may shorten battery operation.

The creator of this application assumes no responsibility for any events that occurred using this application.

[Source]
Geospatial Information Authority of Japan (GSI)
「The bathymetric contours are derived from those contained within the GEBCO Digital Atlas, published by the BODC on behalf of IOC and IHO (2003) (http://www.gebco.net)
海上保安庁許可第292502号（水路業務法第25条に基づく類似刊行物）」
Shoreline data is derived from: United States. National Imagery and Mapping Agency. \"Vector Map Level 0 (VMAP0).\" Bethesda, MD: Denver, CO: The Agency; USGS Information Services, 1997.
「データソース：Landsat8画像（GSI,TSIC,GEO Grid/AIST）, Landsat8画像（courtesy of the U.S. Geological Survey）, 海底地形（GEBCO）」
Images on 世界衛星モザイク画像 obtained from site https://lpdaac.usgs.gov/data_access maintained by the NASA Land Processes Distributed Active Archive Center (LP DAAC), USGS/Earth Resources Observation and Science (EROS) Center, Sioux Falls, South Dakota, (Year). Source of image data product.

OpenTopoMap
opentopomap.org