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Sketch Maps
(Click here for a PDF version)
Many different types of maps are drawn in the course of archaeological work. Sketch maps show the general location and layout of sites; more formal site maps document artifacts and excavations; "plan view" maps show the distribution of soils, features, or artifacts on an excavated surface; profile maps show soil and sediment horizons. All of these maps are meant to document information of archaeological importance.
Sketch maps, as all good formal maps, should contain the following elements:
-- a north arrow
-- a scale
-- a key
-- date, name, and project
-- information putting the map in wider spatial context
The north arrow should be labeled "north" or just "N". Maps are conventionally drawn so that north is at the top of the page, although this is not always the case. It is not necessary to include east, west, and south with your north arrow. Profile maps should include a direction indicator – often this is given in text such as "west wall of test unit" or "profile of stream bank, facing south".
Although Rudyard Kipling wrote, "east is east and west is west, and never the twain shall meet", there are several different definitions of north:
Polar north or "true" north is the direction to the northern axis about which the earth rotates. This can be determined through astronomically based observations or by correcting observed magnetic north for known magnetic declination. You will usually not have to determine true north unless you are constructing a formal map of a site.
Magnetic north is the direction a compass needle points – depending on where you are, this may or may not parallel polar north. Magnetic north is probably the most common type of north used in archaeology.
Grid north is simply the direction designated north from a provenience grid or base line that has been established out on the ground. It may or may not correspond to true north or polar north. Grid north is often useful in situations where you cannot determine any other type of north with any accuracy, or when there is an existing and useful base line of some sort which is an expedient proxy for north or which is central to any map or project. This may be a road, railroad, pipeline, river, or similar linear object.
"Road north", for example, is defined in relation to a specified road. It parallels north-south trending roads and crosses east-west trending roads at a 90 degree angle. It changes as the road turns. If you are driving from Fayetteville to Neosho on Highway 71, you are traveling "road north" the entire way, even though you will be traveling closer to magnetic east and west some of the time. If you draw a map oriented with some sort of "grid north", it is important to specify the base line of the grid.
The scale should be drawn graphically, like this:  , not just given as a ratio (i.e. 1 cm = 3 km). If a map is enlarged or reduced through photocopying, a graphic scale is enlarged or reduced with the rest of the map, but a ratio scale becomes useless. Vertically exaggerated maps should have a graphic scale on both the horizontal and the vertical axes.
Many sketch maps are drawn simply to give the location of a certain site or to show the relationship between certain elements on the map, and these maps may not have a consistent scale. If this is the case, be sure to write "not to scale" on the map. "Not to scale" maps can still include distances written out between locations.
A key describes what the map symbols represent. A key to symbols may be drawn along the edge of the map in a box (i.e.  = forested area), or mapped elements may be described directly on the map where they occur. Don't assume that any map symbol is universal or easily interpreted. A long straight line with short orthogonal crossing lines (like this:  ) may represent a railroad, a fence line, a levee, or an undetermined or gradual boundary between two distinct areas. Click here to see some commonly used topographic map symbols.
Every map should include a date, the name of the map's author, and the project for which the map was drawn. Be careful to write legibly and to avoid abbreviations which may not be easily interpreted in the future.
Be sure to include information putting the map in a wider spatial context. On an informal sketch map, this may just be the project name and a few labeled roads or landmarks. More formal maps should be put in a context easy enough for anyone to understand. Often this context will be apparent from the surrounding text in a report or a book – sketch maps drawn in the field may easily become separated from any supporting documents and should be able to stand alone.
Please remember that others looking at your map (perhaps decades later) may not have access to the same information you do, and they may be looking at the map completely out of its original context. A good map will stand alone and convey its full information without supporting documents.
To recap: when you draw a map, anybody should be able to look at it and easily answer the following questions:
Which way am I facing? (North arrow)
How big is that thing? (Scale)
What in the world is that? (Key)
Who made this, when did they make it, and what were they doing? (Date, Name, and Project)
How do I find this place? (Context)
* * * * * * * * * * * * *
A cautionary tale of maps from Lewis Carroll's The Hunting of the Snark:
The Bellman himself they all praised to the skies –
Such a carriage, such ease and such grace!
Such solemnity, too! One could see he was wise,
The moment one looked in his face!
He had brought a large map representing the sea,
Without the least vestige of land:
And the crew were much pleased when they found it to be
A map they could all understand.
"What's the good of Mercator's North Poles and Equators,
Tropics, Zones, and Meridian Lines?"
So the Bellman would cry: and the crew would reply
"They are merely conventional signs!
"Other maps are such shapes, with their islands and capes!
But we've got our brave Captain to thank"
(So the crew would protest) "That he's brought us the best –
A perfect and absolute blank!"
This was charming, no doubt: but they shortly found out
That the Captain they trusted so well
Had only one notion for crossing the ocean,
And that was to tingle his bell.
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