Marginalia Information (information about the map)
This section offers guidelines to ensure a consistent approach to adding information to your map – cartographers call this composing your map.In alphabetical order the contents of this section are:
» Explaining Some Jargon - Graticules and Grids
» No ‘Hard’ Rules
» North Arrow
» Production Information
» Two Examples – Differences Discussed
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
» North Arrow
» Production Information, including authorship and date
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.
These are two typical climate graphs. The point to notice is that once a decision is made to include a climate graph(s) the design of how this is done is up to the map maker’s discretion.
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').
The title is always the largest font size on the sheet, is often in capital letters, and placed in a prominent place. If a note is included it is usually in a smaller sized font to the main title.
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.
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)
Keep the design of your symbols simple and as different from each other as possible. Where possible use existing ‘standard’ symbols – eg blue line for the coastline.
These are two examples of legends from 1:250,000 scale maps, but each doing a slightly different thing. The first is from the ICSM Harmonised Data Model and is a list of Standardised Topographic Symbols. This shows the symbol, gives its name and a brief explanation of what is included in that name. This techniques is very common for specialist maps – for example geology or soils, where the legend might describe the composition and ⁄ or evolution of a rock formation or soil type. Indeed for some of these type of maps the legend may be larger than the map.
The second assumes an understanding of what the symbol means, and it simply shows the symbol and its name.
Legend and Title are the two elements of a map which are fundamental to a map being understood and used in the way intended by the map maker. This map is an example of what can go wrong if a map does not have a Title and ⁄ or a Legend.
This is a map from a report and it shows the location of tide gauges in Australia. When it is with the report it is a useful map, but away from the report, it becomes a confusing list of places on the coast of Australia, with no apparent reason for their choice.
Please note that all the other marginalia items which are discussed below are not included on this map, but the map is still successful because it is a simple map, of a well known area.
→ Read more about map symbols and legends in A Map Users Guide to Reading Tactual and Low Vision Maps.
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.
In this digital era it is important to remember that a printed map can be easily enlarged or reduced (most photocopiers are able to do) or can be turned into an electronic map (as is typical on the internet). When either of these happen it is important to note that:
- the Scale Bar will remain correct
- the written Statement of Scale will not be correct
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
These are examples where both a Scale Bar and a Statement of Scale have been used. Note that they are positioned close to each other for ease of reading and that the second offers two measurement scales – to aid more precise estimation of distances.
This is an interesting example where a Scale Bar supplies two different measurement systems. It was part of a map which had significant amount of land (Kilometres) and ocean (Nautical Miles) information.
This is part of scale bar from a navigation chart – it is "hedging its bets" as to who will be its users: land transport (Kilometres), marine or air navigators (Nautical Miles) and land measurement (Statute Miles - US & UK primarily).
→ Read more about map scale in A Map Users Guide to Reading Tactual and Low Vision Maps.
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.
The location of the map on the Earth is shown by using two methods. One or both may be included on a map.
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:
In this example, the Location Diagram is an inset into the map. The extent of the map is indicated by the red square in the diagram and this allows the map user to locate the position of the map relative to the whole of Australia.
It would also have been perfectly acceptable to use a map of Western Australia as the base map for the Location Diagram – the decision would come from the map maker’s understanding of who the map user would most likely be and how much they would understand the geography of the area.
In this example, the location diagram is shown in the margins of the map and not regarded as an inset to the map. It is doing an additional thing when compared to the previous example. It is still identifying where the map is in the world (in this case using a Queensland base map), but it is also showing the surrounding maps in this series of topographic maps.
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:
|level of ambiguity of location of the map||needed by map user?||show latitude and longitude?|
|not ambiguous||not needed||don’t show|
|not ambiguous||desired||show latitude and longitude values at all four corners and ⁄ or a selection of points within the map|
|not ambiguous||needed||show a selection of latitude and longitude lines and their values|
|ambiguous||not needed||don’t show|
|show a regular number of latitude and longitude lines and their values (in this situation the density of the lines increases as ambiguity and ⁄ or need increases)|
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.
These two maps are of the same part of the Earth and use the same projection. The one on the left has a grid and the one on the right has the coordinate system shown (a selection of lines of longitude and latitude).
Differences to note are:
- the different shape and size of each ‘cell’ — for the grid system they are always square and the same size, for the coordinate system the shapes and sizes change from north to south.
- if you are given the coordinates of a feature you can locate it anywhere on the surface of the Earth, using any map which has longitude and latitude shown
- if you are given the grid reference of a feature you can only locate it using the map it is based on – the only exception to this is if the grid reference is part of a well known system (please see the section on UTM Map Grid and the Australia Map Grid)
- with the coordinate system (longitude and latitude) there is an assumption that a map user understands the system
- with the grid system there is no such assumption.
→ Read more about map reference systems in A Map Users Guide to Reading Tactual and Low Vision Maps.
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
North Arrows can be as simple or as complex as the map maker wishes. These are a few examples of commonly used North Arrows.
This is a North Arrow which was part of a map where north was not at the top of the map, rather it was to the left hand side of the map sheet. The second is the same arrow tilted to indicate a situation when north has been positioned in the top left hand corner of the map sheet.
This is a North Arrow from a 19th Century map which was bound into a book. It shows features around a long, narrow, east-west aligned bay. To show the features in as great a detail as possible the map maker decided to align the map in an east-west direction (i.e. with north to the right-hand side of the map).
The advantage of this was that map could be folded out from the book and therefore features shown in greater detail than would otherwise be possible if it had been produced at the same size as the book.
Whenever North is not at the top of a map a North Arrow must be shown on the map.
This is an example of a complex North Arrow.
It is typical topographic map North Arrow in that it identifies the location of True North, Magnetic North and Grid North. One interesting feature is that it states the rate (in degrees) that Magnetic North in moving – this is very important to map users when using compasses for navigation.
A related subject is Magnetic Bearing which is explained in the Surveying for Mapping.
→ Read more about map direction and orientation in A Map Users Guide to Reading Tactual and Low Vision Maps.
Where possible, maps should include production notes (some times called 'map credits' but more usually these days: metadata). Important items are:
- 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
- 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)
- a Copyright statement (including the Copyright symbol ©)
Two Examples – Differences Discussed
These two maps are examples of the choices a map maker is faced with when deciding what marginalia is included and how it is handled.
The first is a simple general reference map of Australia and the second is a more complex maritime zones management map.
The marginalia for both is excellent – there are no ambiguities, and the maps can be easily understood. In the case of the maritime zones map, where there is potential for confusion about a feature is (ie what a maritime boundary means) there has been additional information supplied in the form of explanatory notes.
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:
» North Arrow
» Production Information, including authorship, date
This map is an excellent example of how a map can remain very successful with a minimal number of marginalia items:
The thinking behind the marginalia information on this map.
|Maps Purpose||This map is the cover of a brochure which was made to advertise the availability of overseas study scholarships (called Fellowships) for people living in New South Wales.|
Therefore its purpose was to encourage people to ‘pick-up’ the brochure and read its contents.
|Maps Design||A simple, colourful design was chosen.|
Without any marginalia information it succeeds in conveying the message of movement away from New South Wales to the rest of the world. The marginalia information is used to enhance this message.
|Location||In this simple design, of a well known area, no location information is required.|
|Legend||Because the symbols used are clearly understood (arrows to suggest movement) a legend was not required.|
|North Arrow||Again, because this is a well known area, and north is to the top of the map, a north arrow is not required.|
|Production Information||In this instance, because the scholarships are provided by the New South Wales Department of Lands, the author of the map is clearly identified in the south-east corner of the map.|
|Projection||Projection information is irrelevant to the purpose of this map and has therefore not been supplied. |
However its shape suggests that it is most likely a Mercator projection.
|Scale||This is also irrelevant to the purpose of the map and has therefore not been supplied.|
|Title||As stated above, this is generally considered to be an essential part of any map. In this case an extensive title, which fully explains the purpose of the map, is supplied in the north-east corner of the map.|
- B E Goodrick – A Map Users Guide To Reading Tactual and Low Vision Maps
- Wikipedia – Cartography
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phone: +61 2 6249 9677 (international) or (02) 6249 9677 (within Australia); email: email@example.com