Explaining Some Jargon – Map and Marginalia

Maps have two basic components:
    » the map itself (commonly called the ‘face of the map’); and
    » information about the map (commonly called ‘marginalia’).

The term marginalia comes from a convention that all additional information about the map was printed ⁄ drawn outside the edge of the map – i.e. in the margins.  This convention has disappeared with time, but the term lives on.

There are no hard–and–fast rules as to what marginalia should accompany a map, but there are some well recognised principles which are outlined below.

Also, there are no real rules as to how the marginalia should be shown on the map – it is completely up to the map maker’s discretion.

The marginalia items which are discussed here are:
    » Graticules and Grids
    » Legend
    » Location
    » North Arrow
    » Production Information, including authorship and date
    » Projection
    » Scale
    » Title

These are by no means the only marginalia items – this also is completely up to the map maker’s discretion.  A good example of this is the climate graphs which are now regularly added to topographic maps – especially larger scale topographic maps.

Title

It is essential that a map has a title.  This is to ensure that the reader knows what is being mapped.  This may be very simple (e.g. 'Australia') or made more complex by including a note outlining the content ⁄ purpose and ⁄ or limitations of the map (eg 'Australia – not to be used for navigation', or 'Railways of Australia').

On rare occasions a map may not have a title.  This is only acceptable if the legend clearly describes what the map is showing.  However, this is not a preferred practice and should be avoided.

Legend

A legend is essentially a decoder for all the symbols used on a map.  Remember it is not always intuitive as to what a symbol represents, so give sufficient information to ensure that your map is not misread.  For example a tree symbol could represent a single tree, a forest, a plant nursery, a city park, a lawn cemetery or even something totally unrelated to plants.

As a general rule a map should always include a comprehensive legend which explain ⁄ defines the meaning of the symbols used.  This removes the risk of a map being misinterpreted and ⁄ or used incorrectly.  In cases where space does not permit all symbols to be shown in a map legend, the more obvious ones could be omitted (for example rivers and ⁄ or roads are relatively easily interpreted by map users).  However, this is best avoided if possible.

Very simple maps (such as an outline map of a country’s borders) may not require a legend.  Items which can be used instead of a legend include:

• adding text to describe each feature on the map – this removes ambiguity
• use of well known symbols ⁄ colours etc to identify features (for example continuous thin blue lines usually indicate watercourses and roads are often depicted by red lines)

→   Read more about map symbols and legends in excerpt from A Map Users Guide to Reading Tactual and Low Vision Maps

Scale

The majority of maps need the scale to be stated (maps without scales are essentially diagrams).  This should always be given by Statement of Scale (eg 1:1,000,000) and ⁄ or by showing a Scale Bar.  Refer to the section on scale. 

The decision as to which of the following alternatives is used is usually based on:
        »   the purpose of the map
        »   an assessment of the needs of the map user
        »   likelihood of being photographically or electronically enlarged or reduced

These are the four alternatives a map maker has to choose from:

• Showing both
  • Where the scale is consistent across a map, a Statement of Scale and a Scale Bar are often shown.  Also, if a map is to be used for a legal purpose, it is likely that both would be required.
• Showing a Scale Bar only
  • This is emerging as the most common way to show scale on a map – because of the issues associated with photographic ⁄ electronic enlargement or reduction of a map. 
• Showing a Statement of Scale only
  • This is less preferable to either of the two previous alternatives, because of the issues associated with photographic ⁄ electronic enlargement or reduction of a map.
• Showing neither
  • Where the scale is highly variable across a map (such as with some world maps) or the scale is not important as the map is of a well known ⁄ identifiable area it is acceptable that no scale information be shown.  This should however be regarded as the ‘exception, not the rule’.

Where the scale of a map is highly variable and ⁄ or distorted away from the Standard Parallel(s) it is common to have additional information supplied with the Statement of Scale ⁄ Scale Bar.  Most commonly this involves suppling location information about the scale.  For example:
        »   scale at the Equator (or Equatorial Scale) is …, or
        »   scale at 20° North or South is …, or
        »   scale at the Standard Parallel(s) is …

Statement of this nature should be interpreted to mean that the scale is only for the location identified and that it will be different in other areas of the map.

Where a map is comprised of many variously scaled maps (e.g. for islands in the Pacific Ocean very small islands are shown at a different scale to larger islands) information needs to be supplied about the scales on each map using one or both methods.

Examples of Scale Bars

→   Read more about map scale from an excerpt from A Map Users Guide to Reading Tactual and Low Vision Maps.

Projection

The amount of information supplied regarding the projection used for the map is dependent on the purpose of the map and ⁄ or the complexity of the projection.

In simple terms this equates to:

• Simple maps may not require projection information to be shown, but it can be added if desired.  A good example is a town ⁄ city, holiday resort map where the important factor is that a consistent scale is used and that features stay in their correct position relative to each other. 
• Larger area and more complex maps ⁄ projections need some projection information to be shown. 
• Legal maps and very complex ⁄ unusual projections need precise information about the mathematics behind the projection – e.g. a map of prohibited area.

Note: projection information is often sought by map users, sometimes many years after a map has been published.  For this reason a good rule of thumb is to include projection details where possible.

Location

The location of the map on the Earth is shown by using two methods.  One or both may be included on a map.

Location Diagrams

The first is a simple diagram showing a recognisable region with an indication of the location of the map.  These are called Location Diagrams.  These two are a few typical examples:

Latitude and Longitude

The second is more complex and involves supplying information about latitude and longitude for the area being mapped.  This may be as simple as marking the latitude and longitude values in a number of places on the map (often along the map edges) to showing the lines of latitude and longitude across a map.  Particular latitude and longitude lines of interest may also be show (eg the Tropic of Capricorn on an Australian map).  A more complex method is to show the location of a selection of latitude and longitude lines on the face of the map. 

As with projection information, the decision to provide location information is dependent on a number of variables.  In simple terms the minimum which applies is:

Explaining Some Jargon – Graticules and Grids

In the sections on the Earth’s Coordinate System and About Projections we explained how the earth’s coordinate system is made of lines of longitude and latitude.

Two things need to be noted:

Firstly: Near the Equator a ‘block’ of 1° x1° latitude and longitude is almost a square, while the same ‘block’ near the poles is almost a triangle.

Secondly In the process of projecting these lines of longitude and latitude from the surface of the Earth onto a flat ‘piece of paper’ these lines may be shown as curved lines.

The result of both of these is that understanding lines of longitude and latitude on the face of a map is not necessarily intuitive.  In fact for many map users it can be very confusing.

Therefore for some types of maps an alternate system to the coordinate system has been developed – this is called a grid.  The essence of a grid is that it is a simple design which can be used without the needs to understand the complexities inherent in a coordinate (latitude and longitude) system.

The coordinate system (longitude and latitude) is still needed to create the map, but it is not shown on the face of the map.  It has nothing to do with providing information about where a map is located on the surface of the Earth, although in some instances it may do so.  It is mainly concerned with allowing a feature to be easily found on the map.

Maps which commonly use grids are street directories and tourist maps.

Grids are a regular shaped overlay to a map.  These usually form a square, but they may form a rectangle – they are never another shape.  They usually have a number and a letter to identify zones across a map.  These can be placed at any interval or orientation that suits the map maker and ⁄ or the map user.

→   Read more about map reference systems in A Map Users Guide to Reading Tactual and Low Vision Maps.

North Arrow

Early maps almost always had an arrow indicating the direction to the Geographic North Pole – called a North Arrow.  This convention developed because maps were drawn with no particular reference to the physical reality of the shape of the Earth – rather they were aligned to best suit the subject of the map, for example the route of a trade expedition.

However modern convention dictates that north should be at the top of the map and therefore North Arrows are generally not shown on maps.  The cases where a North Arrow is shown are:

• a map is not aligned with north to the top
• additional directional information is required (eg the direction of both the Magnetic North Pole and the Geographic North Pole)
• north is not clearly defined (eg a map of a not well-known area)

Some map makers simply add a North Arrow for design reasons – because they like the 'look of them' on the map

→   Read more about map direction and orientation in A Map Users Guide to Reading Tactual and Low Vision Maps.

Production Information

Where possible, maps should include production notes (some times called 'map credits' but more usually these days: metadata).  Important items are:

    essential

• a brief statement as to who produced/published the map
• date of publication and ⁄ or date of the information shown on the map
• known limitations of the information

    desirable

• names of organisations and individuals who contributed (information, sponsorship etc) to the map, and ⁄ or names of those who compiled, drew, edited or printed the map
• the methodology that was used to produce the map
• edition (this is not usually added to a first edition map)

    if appropriate

• a Copyright statement (including the Copyright symbol ©)

Two Examples – Differences Discussed

There are no ‘Hard’ Rules when it comes to the amount of Marginalia Information Shown

As the discussion above indicates, there are no set list of the items that every map MUST have.  The only ‘golden rule’ is that the map must clearly ‘tell its story’.  As a general rule a map maker must consider including the following items as part of the marginalia, with the understanding that, in order to prevent someone mis–reading a map, too much information is better than too little:
    » Legend
    » Location
    » North Arrow
    » Production Information, including authorship, date
    » Projection
    » Scale
    » Title

The thinking behind the marginalia information on this map.

Further Reading

B E Goodrick – A Map Users Guide To Reading Tactual and Low Vision Maps

 

Wikipedia – Cartography

http://en.wikipedia.org/wiki/Cartography