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#1
Charlie Frye

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On and off for some weeks now I've been writing a white paper on how to create cartographic quality (topo-sheet worthy) contour lines using ArcGIS with a DEM as input. There is plenty of useful guidance from new and old sources on the nature of, and the desirable traits for contour lines and for generalizing them, but there is precious little when it comes to describing what is good, great, or definitely to be avoided in labeling contour lines. I've compiled a list of from a number of sources including Raisz, Imhof, the USGS, and more--mainly noting that nobody has a complete treatment of the subject. Does anybody have additional guidance, not agree with what I've found, etc.?

Thanks,

Charlie

----------------
Desirable traits in contour labels are as follows:

1. Too many labels are a bad characteristic as the information on the map is covered up.
2. Contour labels should either be oriented uphill or oriented to the page. If the former method is used, then it is generally considered a kindness to map readers to place more labels on the south facing slopes as these will be right side up for reading.
3. The labels should be on a straight base line; curves cause the numbers to be oriented in a fashion that can be difficult to read.
4. Contour labels should be along fairly straight sections of a contour line. This because the label will blank out a portion of the line and the map reader is left to infer the location of the contour line; a straight line is much easier and more likely to be inferred correctly.
5. Do not add extra ink, as it will impede viewing of relevant geographic representations. Extra ink includes such as thousands separators, for example use 1850, not 1,850; and unit of measurement abbreviations, which should be provided as part of the map?s legend.
6. Break the contour lines around and behind the label. A 0.5 point (1/144 inch) gap around the contour label is usually sufficient. This is because the contour label is ideally in the same color as the contour line.
7. Index contour labels are most needed near the tops of ridges, bottoms of valleys, and along dramatic changes in slope.
8. Avoid placing labels on the portions of contour lines that trend north to south.
9. Do not ladder or stagger labels to form any sort of obvious pattern. The key word is obvious; as subtle patterns will actually help map readers in finding additional contour labels quickly. Obvious patterns will jump out at map readers, not only distracting them, but also creating false patterns in the landscape.
10. Among other items from the USGS: good judgement on the part of the cartographer and editor.

Thus, a subtly patterned, though nearly random looking scheme for placing contour labels would seem to satisfy the spirit of what is needed without causing unnecessary labor on the part of the map reader. Some have argued that random placement of contour labels is a better option. The problem with random placement is that it requires more labels to be placed in order to make it sufficiently easy to find a label.

Others have argued that contour labels can be placed in patterns that reinforce the shape of the terrain. While this is certainly possible, it also requires a great deal of skill and experience to properly apply such a technique; that skill may no longer exist and the specific methods for labeling contour lines on each given landform apparently were not codified in a comprehensive manner. To even consider this method requires a two-stage process, first identifying the landforms and second having a specific strategy for placing contour labels on each landform--neither stage is currently understood well enough to automate.
----------------------
Charlie Frye
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#2
Martin Gamache

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Charlie,

I usually create a grid and first label all spot elevations and prominent saddles, peaks, water bodies and other points. Once that is done I auto-label a segmented version of the contours and then go through the grid, cell by cell and start deleting labels and moving labels so that I have one elevation label per grid placed along a straight non N-S line segment and not obstructing an important landmark/terrain shape if possible. I don't strictly enforce the grid density but try to to maintain consistent elevation label density across the sheet. I only label index contours and if there is already a spot elevation label in the grid unit I don't put a contour label. The size of the grid determines my label density and is adjusted according to the scale of the map and the size of the labels. I don't have an exact formula for this ( probably a Master's thesis in determining if there would be an ultimate "sweet" density). Along with the elevation labels I also check for other labels to maintain ink density and not have too many labels in one place if they don't need to be there. I also look for consistency in which elevations get labelled. Sometimes you end up with the same height being labelled multiple times in the same vicinity with autolabelling, it's nice to avoid those IMO.

I follow the "Swiss" convention of upright orientation and avoid laddering at all costs. In a surveying course I took we were actually taught to ladder elevations on site plans as that seems to be a convention in the engineering/surveying sector...

I no longer break the line and rather use a halo/stroke around my labels in a one percent tint of the spot color used for the contour and set to overprint. This knocks-out the contour behind the halo and neatly trims the line to the label without having to manually cut the line. I have to credit Pat Dunlavey for showing me that technique. It does require using a spot color for your contours or a pure CMYK ink (i.e. 100% K or C)


In terms of showing landforms I would think that for very flat or slightly sloped areas it is probably important to pay attention to how and where you put labels to communicate which direction is uphill. This is a perennial problem with Orienteering maps which don't use any labels and I am often scratching my head trying to figure out what is up or down.

mg


On and off for some weeks now I've been writing a white paper on how to create cartographic quality (topo-sheet worthy) contour lines using ArcGIS with a DEM as input. There is plenty of useful guidance from new and old sources on the nature of, and the desirable traits for contour lines and for generalizing them, but there is precious little when it comes to describing what is good, great, or definitely to be avoided in labeling contour lines. I've compiled a list of from a number of sources including Raisz, Imhof, the USGS, and more--mainly noting that nobody has a complete treatment of the subject. Does anybody have additional guidance, not agree with what I've found, etc.?

Thanks,

Charlie

----------------
Desirable traits in contour labels are as follows:

1. Too many labels are a bad characteristic as the information on the map is covered up.
2. Contour labels should either be upright, pointing uphill, or all oriented to the page. If the former method is used, then it is generally considered a kindness to map readers to place more labels on the south facing slopes as these will be right side up for reading.
3. The labels should be on a straight base line?curves cause the numbers to be oriented in a fashion that can be difficult to read.
4. Contour labels should be along fairly straight sections of a contour line. This because the label will blank out a portion of the line and the map reader is left to infer the location of the contour line?a straight line is much easier and more likely to be inferred correctly.
5. Do not add extra ink, which will impede viewing of relevant geographic representations. Extra ink includes such as thousands separators, for example use 1850, not 1,850; and unit of measurement abbreviations, which should be provided as part of the map?s legend.
6. Break the contour lines around and behind the label. A 0.5 point (1/144 inch) gap around the contour label is usually sufficient. This is because the contour label is ideally in the same color as the contour line.
7. Index contour labels are most needed near the tops of ridges, bottoms of valleys, and along dramatic changes in slope.
8. Avoid placing labels on the portions of contour lines that trend north to south.
9. Do not ladder or stagger labels to form any sort of obvious pattern. The key word is obvious; as subtle patterns will actually help map readers in finding additional contour labels quickly. Obvious patterns will jump out at map readers, not only distracting them, but also creating false patterns in the landscape.
10. From the USGS: good judgement on the part of the cartographer and editor.

Thus, a subtly patterned, though nearly random looking scheme for placing contour labels would seem to satisfy the spirit of what is needed without causing unnecessary labor on the part of the map reader. Some have argued that random placement of contour labels is a better option. The problem with random placement is that it requires more labels to be placed in order to make it sufficiently easy to find a label.

Others have argued that contour labels can be placed in patterns that reinforce the shape of the terrain. While this is certainly possible, it also requires a great deal of skill and experience to properly apply such a technique; that skill may no longer exist and the specific methods for labeling contour lines on each given landform apparently were not codified in a comprehensive manner. To even consider this method requires a two-stage process, first identifying the landforms and second having a specific strategy for placing contour labels on each landform--neither stage is currently understood well enough to automate.
----------------------



#3
Charlie Frye

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I like the 1% screen trick and the addition of putting the spot heights; the USGS recommended not placing labels near the spot heights.

One trick I thought of in reading your post was that the ArcGIS annotation data model has an Angle field, which could be queried for using an attribute query:

([Angle] > 80 AND [Angle] < 100) OR ([Angle] < -80 AND [Angle] > -100)

That way you could get the near vertical labels in one pass. I suggest marking them as unplaced; so you can use them in later editing.
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#4
Martin Gamache

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the addition of putting the spot heights; the USGS recommended not placing labels near the spot heights.


I consider spot elevations and contour line labels to be all part of the same information class...elevation. So I try and make sure the two label sets work together. If I'm going to put a label in one place I don't want another label saying the same thing very close to it.

#5
Mike H

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There are times and places where a ladder system works well for elevation text. The Ordinance Survey maps use this technique, and although I wouldn't want to impose it as a hard rule, sometimes it is helpful to get a sense of the relief in hard numbers at a glance. I attached a lo-res crop of two maps where I designed with a ladder system for elevation text - both recreational maps, so the data was relevant to the users at a glance. One is the Appalachian Trail in Maine, the other Sugarloaf/USA (Maine) XC ski trail system.

This is what I love about design - everytime you try to make a rule, someone can pose an instance where it maybe-kinda-sorta could be broken, or at least bent a little!

m.

Attached File  Hermann1.jpg   352.36KB   372 downloads
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#6
BEAVER

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Mike. What kind of map is the one you are showing Appalachian Trail in Maine of ?

#7
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Martin - three cheers for that overprint/1% trick, I have been longing for an easier way to do things like that for quite some time!
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#8
Mike H

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Mike. What kind of map is the one you are showing Appalachian Trail in Maine of ?



It is part of the seven map series that the Maine Appalachian Trail Club (MATC) publishes of the AT in Maine. Geno Carpentier and I designed the maps in 2003-04, for MATC, and they are the current product in the retail market (edition 14). They are specific to hiking the AT, printed on HopSyn, and sold as a bundle with the 7 maps and a guidebook.

You can read about the project workflow in Cartographic Perspectives # 53 (Cartographic Techniques).

m.
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#9
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Charlie,

Great initiative.

I remember the days when I had to put opaque on scribe coats to mask out contour lines..

I am a not an experience map designer, however like some others pointed out various techniques exists for various scenario. ... Thanks for all those tricks...

Anyway here is my small addition to your efforts.

....
3. The labels should be on a straight base line; curves cause the numbers to be oriented in a fashion that can be difficult to read.
4. Contour labels should be along fairly straight sections of a contour line. This because the label will blank out a portion of the line and the map reader is left to infer the location of the contour line; a straight line is much easier and more likely to be inferred correctly.
6. Break the contour lines around and behind the label. A 0.5 point (1/144 inch) gap around the contour label is usually sufficient. This is because the contour label is ideally in the same color as the contour line.


(3,4)I am not sure if this should be a rock solid guideline. First if labels are place on a relatively straight portion of the contour I believe it can follow the contour line (hence curved text along line). If it is very subtle I don't think it is a problem for the reader.
(6) Also, do we really have to break the line under the label... if the reader can see the continuity of the line without hampering its legibility all the better?.

I have attached a small sample to make or Brake my points...
PS the values are meters.
Chart

#10
Martin Gamache

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(6) Also, do we really have to break the line under the label... if the reader can see the continuity of the line without hampering its legibility all the better?.



IMO it is much cleaner looking and more elegant to not have the two overlap. Depending on the font and label size you use it can also make your labels easier to read. Anyways it is not so hard to buffer the label so why not?

#11
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(6) Also, do we really have to break the line under the label... if the reader can see the continuity of the line without hampering its legibility all the better?.



IMO it is much cleaner looking and more elegant to not have the two overlap. Depending on the font and label size you use it can also make your labels easier to read. Anyways it is not so hard to buffer the label so why not?


Martin,
I think your point about being more elegant is correct. And as you say it is not too hard to Buffer the label. However I would think it is more difficult to actualy mask the line instead of buffering the label?
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#12
Martin Gamache

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As I explained in my previous post you can use the label buffer as a mask. I'm sure you could also write or find a script that could create a small label sized/orientated box that could be used to systematically clip and delete the interection section of all the contour lines if you really wanted to cut the lines.

mg

#13
Hans van der Maarel

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I no longer break the line and rather use a halo/stroke around my labels in a one percent tint of the spot color used for the contour and set to overprint. This knocks-out the contour behind the halo and neatly trims the line to the label without having to manually cut the line. I have to credit Pat Dunlavey for showing me that technique. It does require using a spot color for your contours or a pure CMYK ink (i.e. 100% K or C)


Any chance of getting some more detailed instructions on this? I've been trying to emulate it, but didn't really succeed (the fact that I'm using a Dutch version of Illy doesn't help either).
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#14
Martin Gamache

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Hans,

1. Create a spot color. For this to work on press I believe it needs to be a seperate spot color or a 100% pure C, M Y or K ink.
2. Create a 1% tint of that color
3. Draw some lines in your spot color.
4. Type some text (any color).
5. Set a stroke to the text and make it the 1% tint, send it behind the fill, set it to overprint.
6. Turn on overprint preview in the view menu.
7.In previous versions of Illie you had to copy your text and convert your text to path for the mask(outline) part for this to work correctly. I think in CS2 this is not necessary.

Without overprint preview
Attached File  no_opp.jpg   237.71KB   337 downloads


With overprint preview
Attached File  opp.jpg   275.05KB   359 downloads

#15
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As I explained in my previous post you can use the label buffer as a mask. I'm sure you could also write or find a script that could create a small label sized/orientated box that could be used to systematically clip and delete the interection section of all the contour lines if you really wanted to cut the lines.

mg


Yes. Not too hard to do in a GIS environment. Not sure for an Illustrator solution.

I see your moving to Prince George BC.... worked as a technician on the BC TRIM project in Vancouver back in 1990.
Interesting project.. Glacier Mapping.
Good luck with your Masters... off topic but what is your subject of study.
and looking forward to see your work in the NG.
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