Reading “GSI” Topographic Maps

GSI Topo Maps: A Beginner’s Guide

In this previous article I described in some detail the finer points of reading “Yama to Kogen Chizu” topographic maps, this time we turn our attention to the Geospatial Information Authority of Japan (GSI) and notably their detailed 1:25,000 topographical map series that covers the entire country. These survey maps serve as a basis for establishing land boundaries and roads though are also invaluable for hikers looking to glean information about the terrain, natural features, and man-made structures depicted by the surveyors.

While GSI publishes maps at a variety of scales, the focus here are the 1:25,000 topo maps, where 1 centimetre on the map represents 25,000 centimetres, or 250 metres, on the ground. In particular, I have tried to hone in on the topographic map legend and symbols GSI uses to represent vegetation, landforms, landmarks, water bodies and paths. Decoding this iconography isn’t immediately intuitive, with a lopsided ‘Q’ representing broad-leaved forest and an inverted ‘V’ for coniferous forest. However, understanding the symbols and recognising them out on the trail offers up clues to better navigate our surroundings.

So, which one is ‘best’—the GSI or Yama to Kogen map? Most of the time, it’s sufficient just to carry the Yama to Kogen Chizu which is geared towards recreational climbing. They are updated annually, include information on the location of water sources, campsites, and course times, are compact when folded up, and are made from water- and tear-resistant paper. The GSI map sheets, on the other hand, are useful when the hike falls outside one of the Yama to Kogen map sheets or in situations where you need the extra detail of a small-scale map. The contour lines are easy to see, packs in far more detail and are significantly cheaper (435 yen) for multicoloured and a bit less for the former three-coloured maps vs. 1,100 yen for Yama to Kogen Chizu). Both map styles are readily available at large bookshops and outdoor stores.

The GSI maps are less focused on hiking and more on conventional navigation, which requires a knack for reading them, hence the rationale behind writing this blog post, which can make hiking more enjoyable and perhaps lessen the possibility of getting lost. Paper maps are best used in conjunction with a handheld or smartphone-enabled GPS device with preloaded topographic maps.

Contents

Vegetation Features
Landforms Features
Water Bodies
Buildings and Landmarks
Roads and Trails
Navigational Aids not Shown on GSI Maps

  Vegetation Features

1. Broad-leaved Forest　広葉樹林　kōyōji-yurin 

Broad-leaved forests can be classified as evergreen “laurel” forests found in the warm temperate / low alpine mountain zone from Honshu to Kyushu or cold temperate / mountain zone deciduous forest from southern Hokkaido to Kyushu. The broad-leaved forest symbol represents places where hardwood forest grows to a height of at least 2 metres.

2. Coniferous Forest　針葉樹林　shinyōji-yurin 

Coniferous trees are mostly found in Japan’s plantation forests established after the Second World War. Cedar, Japanese cypress, and Japanese larch trees occupy nearly 90 percent of the plantation forests. The coniferous forest symbol indicates softwood trees and saplings of at least 2 metres.

3. Bamboo Grass Zone　笹地　sasa-chi 

Sasa or bamboo grass is a common feature on or near the ridgeline. The bamboo grass zone denotes sasa less than 2 metres, meaning in most cases you’ll have an unobstructed view. Note that the map symbol is similar to bamboo forest.

4. Bamboo Forest　竹林　chiku-rin 

Groves of bamboo or take can be found in a range of environments including lowland mountains and along river verges.

5. Creeping Pine Zone　ハイマツ帯　haimatsu-tai 

Pinus pumila or creeping pine, is native to north-eastern Asia. In Japan, it is distributed from Hokkaido to the Chubu region, with its southern limit at Mt. Tekari in the Minami Alps. On high alpine ridgelines, it ‘creeps’ along the ground, though grows taller in subalpine forest. The zone it occupies is exposed to the elements, so be mindful of the weather when hiking through it.

  Landform Features

6. Earth Cliff　土崖　dogai 

An earth cliff is represented by steep slope with a height of at least 3 metres and a length of more than 75 metres. They are formed when the surrounding ground collapses. Comprehending the full extent of the cliff and distinguishing it from its surroundings means it not always helpful for marking your position.

7. Crater　噴火口　funkakō 

This symbol is used to indicate craters with active fumaroles or, in the case of volcanoes, where eruptions may occur but are currently dormant. Volcanic gases can arise from the hillside as well as top of the crater.

8. Crag　岩崖　iwa-gake 

In a similar vein to the earth cliff, for a rocky precipice to be marked on the map, it needs to be at least 3 metres in height and 75 metres in length. As it usually presents with prominent rocks and gravel in the surrounding terrain thus it cannot be reliably used to mark your position.

9. Rock　岩　iwa 

This mark is used to designate a rocky area rather than individual rocks. If the rock-strewn area extends over a wide zone, you will struggle to determine your specific location.

10. Rough Forging　荒地　are-chi 

In mountain areas, the rough forging symbol denotes grassland and shrubland characterised by an unencumbered view.

11. Gravely Sand　砂礫地　sare-kichi 

Gravely sand represents areas, as you probably guessed, layered in sand and gravel. It can be observed in a wide variety of places, including sandy beaches, riverbanks covered with small stones, and islands such as Mt. Tenjo on Kozushima. In the Japanese Alps, this kind of terrain is often seen through the alpine zone.

  Water Bodies

12. Pond　池　ike 

Regardless whether it’s natural or artificial, ponds and swamps with a size of 25 x 25 metres or more that remain full are indicated on the map. Ponds located near mountain trails can be used to get a general sense of your location.

13. Wetland　湿地　shicchi 

For an area to be designated as a wetland it needs to maintain a size of 75 x 75 metres or more.

14. Perennial Snow Patch　万年雪　mannen-yuki 

Perennial snow patches occur in snowy valleys where snow and ice remain year-round. There are various sizes, but to be indicated by this symbol it should be 50 x 50 metres or more in September. It is seldom seen except in some alpine areas, and the boundaries shown on the map may differ depending on the climate.

15. Weir / Dam　せき　seki 

Ever-present along rivers and valleys in Japan to regulate the flow for irrigation, hydropower, and water supply.

  Buildings and Landmarks

16. Building　建物　tatemono 

Small buildings such as mountain huts and refuge shelters are usually indicated, making it simple to know your precise location. Note that minor structures such as agricultural equipment sheds, lean-tos, and gazebos may be omitted.

17. Transmission Line　送電線　sōden-sen 

Power transmission lines run deep into the Japanese mountains, soaring even above 1,500 metres, making them useful landmarks. Hiking trails often pass near transmission towers making it easy to grasp your whereabouts.

18. Radio Mast　電波塔　denpotō 

Radio masts and towers are often erected on the summit of low-lying mountains and can be glimpsed from long distances, making them handy landmarks even if they’re a blight on the landscape.

19. Windmill　風車　fūsha 

Electricity generating wind turbines can be seen dotted on coastal hillsides or grouped together as part of a ‘wind farm’. Their propeller-like blades can be easily spotted making them useful to get your bearings.

20. Triangulation Station 三角点　san-kakuten 

A triangulation station or trig point is a fixed surveying station with known coordinates and elevation and are useful to hikers as navigational aids. In Japan they are square pillars fashioned from granite and divided into five classes. The one in the photo is a class two trig point of which there are about 5000 installed every 8 kilometres.

  Roads and Trails

21. Mountain Path　徒歩道　tohodō 

The standard dashed line symbolising a mountain path has a width of less than 1.5 metres. Note the veracity of mountain trails and branches can’t always be relied upon as they may be out of position or not actually exist. Check YamaReco and YAMAP for the latest mountain climbing conditions.

22. Road width less than 3 metres　幅員3.0m未満の道路 

A fine black line indicates a road width of 1.5 to 3 metres. Normally these are forestry roads leading up to mountain trails some of which are paved and some of which are aren’t.

23. One-lane Road　一車線道路 

A step up in road hierarchy finds paved, one-lane roads. Frequently, these roads branch off, narrow or alternate between sealed and unsealed segments.

24. Aerial Lift　ロープウェイ　rōpuwei 

This braided line shows the location of cables coupled to an aerial lift or “ropeway” such as cable cars, gondolas, and chairlifts. If the area around the ropeway is exposed, it can serve as a landmark for navigation.

  Navigational Aids not Shown on GSI Maps

25. Rock Cairns　ケルン 

One final feature worth mentioning that isn’t marked on the GSI maps yet functions as a navigation aid are cairns or human-made stacks, mounds, or piles of rocks. They can be found on summits, along ridgelines and sometimes at trail branches.

— Map symbol inlays and feature image courtesy of Geospatial Information Authority of Japan (GSI)