26 replies to this topic

[Sky Schemer]

it has become a subtractive enterprise in which mapmakers start with an overly complex database and take stuff away until they can stand to look at it.

Is this so-called subtractive approach inherently bad, though? I see it as a tool, and like any tool you can use it well, use it sloppily, or use it for the wrong job.

[Dennis McClendon]

Would you compose a poem by starting with a lengthy essay and deleting the unneeded words?

Would you landscape a garden by just weeding the existing plot of land?

Or draw a cartoon by using whiteout on a photograph?

Mapping has at its very core abstraction. Otherwise we'd just label an aerial photo.

Abstraction comes from understanding the meaning of something. Is this street important enough to be on the map? Are the actual banks of this stream (at some moment in the past) necessary to understanding of its existence?

I suppose I should just make my sig on this board the aphorism attributed to Antoine de Saint-Exupery: "Perfection in anything at all is attained not when nothing more can be added, but when nothing more can be taken away."

Ironically, in a graphic context, you best achieve the desiderata of being able to take nothing more away by starting with nothing at all.

[Sky Schemer]

Mapping has at its very core abstraction. Otherwise we'd just label an aerial photo.

Abstraction comes from understanding the meaning of something. Is this street important enough to be on the map? Are the actual banks of this stream (at some moment in the past) necessary to understanding of its existence?

Your assumption here is that the subtractive process is the only tool employed, and I agree that this would be a poor use of the tool. But it doesn't have to stop there: one can select the data and then abstract it. And it is hardly the same as just deleting elements and publishing what remains.

Even if you are drawing from scratch you are starting with something: another map, an aerial photo, local knowledge, etc. I see little difference between abstracting either starting point.

Maybe we're arguing semantics, though. What you call subtractive may not be what I am calling subtractive.

[peanut]

I think as long as you have a thorough understanding of the data you are looking at a subtractive approach can be beneficial. There is so much high quality data available for cartographic purposes that I think it would be silly not to use it. With proper understanding of your projects and efficient use of queries and generalization tools you can come up with great maps that model the reality you are trying to show. I feel using existing data will allow you produce high quality maps far more quickly than using a completely ground up approach.

Rich

[Dennis McClendon]

Perhaps the difference is between reference maps and thematic maps. A subtractive approach is a perfectly valid tool for a reference map, where the whole point of the map is to see how much information you can cram on.

I view a thematic map as a completely different animal, where the object is to communicate something with a minimum of ink. I view the mall map as being in this category. What is the minimum amount of information needed to communicate the mall's location to the intended audience? It seems unlikely to me that the precise location of 2-metre-wide creeks or nearby trade schools are needed for that purpose. I have never seen a locator map for which I thought the subtractive approach offered any benefit.

[Charles Syrett]

I think as long as you have a thorough understanding of the data you are looking at a subtractive approach can be beneficial. There is so much high quality data available for cartographic purposes that I think it would be silly not to use it. With proper understanding of your projects and efficient use of queries and generalization tools you can come up with great maps that model the reality you are trying to show. I feel using existing data will allow you produce high quality maps far more quickly than using a completely ground up approach.

Rich

I suppose that even when we're drawing, we're engaging a subtractive process -- or perhaps selective would be a better term. I think a lot of this comes down to preference. I always thought of a map as something you draw, and programming as something someone else does. But I've seen some fantastic work done by software manipulation and programming -- Dom's Ships Atlas being a good recent example. Me -- I'd much rather draw!

Another thing, though -- sometimes with the data approach it's easy to forget that you still have to research and find recent developments that just aren't there in your data. You have to find that subdivision plan or that client-supplied air photo and then you're back to drawing again...

Charles Syrett
Map Graphics
http://www.mapgraphics.com

[mika]

Just to stir the discussion a bit more...
Thematic maps - what are they really? If you think about it in a bit more general terms you can include every single map in this category... Ok, ok with some types that evolved into their very special forms, ie. topographic maps, etc. But they are still thematic maps, even though we don't really like calling them that way.
And now, for me a good map is a map that serves it's purpose, no matter what the subject is or the tools employed to create it. So as long as you do the job right it's just fine

And just one more thing. When creating a map, a cartographer creates a very generalized model of the real world (whatever the real world is...). So it looks like there is no escape from the subtractive approach. Not that i don't see the difference between understanding the data and using them with all the cartographic skills and just using a subset of the gis data without even thinking about the influence it might have on the map. But here I am again - no matter what the tools are as long as the final map / product (oh boy, I don't like that word...) is good-->better-->perf***

Dom

[MapMedia]

Subtraction or addition, don't forget to multiple by 'what the client wants' coefficient.

Honestly, for a $150 street map, I might be doing 2 things simultaneously in the first 10 minutes of the project: loading my default basemap and developing the map concept, design scheme in my head. Even still, I heave learned a lot of nifty ways to use the subtractive method to achieve desired effect, esp. when working on short time limits.

Other maps though, I use the additive approach, starting with pencil and paper sketches (ala Philippe Rekacewicz and others) and thinking it all through.

Some of my map clients are engineers, and regardless of my carto sensibilities, the map must show all roads, streams, etc. etc. even if at first they simply gave me a 'concept of the map' to go on. So its good to keep your customer in the equation.

[Hans van der Maarel]

I've split this discussion off from the original thread.

[mika]

I realize that it might be all semantics but:

1. Is the 'subtractive' model understood as creating maps by simply removing some unwanted layers/features from a certain model (scanned map or photograph or gis database) as opposed to the
2. 'additive' model understood as creating a map by adding the layers/features taken from a certain model (scanned map or photograph or gis database).

I ask, because it logically seems to be exactly the same procedure. And the final effect really depends on being skilled and using the data sources in a sensible cartographic manner

Dom

[Charles Syrett]

I realize that it might be all semantics but:

1. Is the 'subtractive' model understood as creating maps by simply removing some unwanted layers/features from a certain model (scanned map or photograph or gis database) as opposed to the
2. 'additive' model understood as creating a map by adding the layers/features taken from a certain model (scanned map or photograph or gis database).

I ask, because it logically seems to be exactly the same procedure. And the final effect really depends on being skilled and using the data sources in a sensible cartographic manner

Dom

You're right -- the part of the cartographic process you're describing is the selective part; never mind "subtractive" or "additive". Perhaps the real issue is how to create a vector line that will actually be part of the final map. I've found that in some cases the most sensible way is simply to use data (or already existing linework in whatever form) and do whatever fast editing may be needed. In other cases, it's far faster, easier, and more enjoyable simply to draw the line.

In our production process, I often reduce one one of our previous maps and load it into the FreeHand file and tell my workers to use the "scavenging" method: use whatever lines are OK as-is and delete/redraw the others. I especially find that complex highway interchanges need to be drawn by hand.

Pat Dunlavey wrote a wonderful treatise a few years ago on the limitations of a data-only approach: http://www.pdcarto.c...rawingBoard.htm

Charles Syrett
Map Graphics
http://www.mapgraphics.com

[mika]

Pat Dunlavey wrote a wonderful treatise a few years ago on the limitations of a data-only approach: http://www.pdcarto.c...rawingBoard.htm

Oh yes, that's classic

And having the article in mind, perhaps, instead of distinguishing between subtractive/additive aproach it's a bit more appropriate to talk about generalisation? So here we go:

1. Subtractive process =~ quantitative generalisation (reducing the amount of objects)
2. additive process =~ qualitative generalisation (simplifying objects)
3. good map design process should involve 1+2 = finding a proper balance between over-generalised map and too complex map = a properly generalised map = a good model of the mapped environemnt

Would you agree with the above statement?

Dom

[Charles Syrett]

Pat Dunlavey wrote a wonderful treatise a few years ago on the limitations of a data-only approach: http://www.pdcarto.c...rawingBoard.htm

Oh yes, that's classic

And having the article in mind, perhaps, instead of distinguishing between subtractive/additive aproach it's a bit more appropriate to talk about generalisation? So here we go:

1. Subtractive process =~ quantitative generalisation (reducing the amount of objects)
2. additive process =~ qualitative generalisation (simplifying objects)
3. good map design process should involve 1+2 = finding a proper balance between over-generalised map and too complex map = a properly generalised map = a good model of the mapped environemnt

Would you agree with the above statement?

Dom

Nice summary. I would also add -- per Chris' previous reminder -- that there's a client in there somewhere! That can impact what you mean by "good".

If anyone ever wanted to write a cartography textbook, they could just go through all these CartoTalk postings and....oh, never mind.

Charles Syrett
Map Graphics
http://www.mapgraphics.com

[Jimbo]

From my understanding of the topic large databases hold the maximum amount of data where the generalization of the objects is required using the subtractive method where additive is adding & the simplifcation of the information. What kind of data is required for the additive process? Do we as Cartographers simply draw by looking at a map & using our memories, or do we simply take a scanned image in order digitize the data? I will also note that the modern cartographer doesn't need a steady hand when you have the technological equipment to do the process.

[MapMedia]

For example: If I am using the additive approach and I decide the map in question really only needs sinuous roads and some buildings, then I could either (1) draw the roads by tracing from other map, or (2) using GIS dataset, simplifying it in GIS and/or Illustrator as needed.

Now I am confused. Did I just give an additive or subtractive example?