[Geomoose-users] best way of creating a .map file to display many classes inside a layer

[bean]

Hello Bob,

I may see things a little differently here. Perhaps some perspective 
might help:

We produce a local machine mapping interface and the data to fill it. 
The subject matter is geology, terrain analysis and land 
management/ownership. We work with reasonably high resolutions of 
about one meter or better in a region of up to 200 square miles per 
map.

Geologists are quite familiar with and frequently use maps with as 
many as 200 different rock types represented on those maps. We have 
taken that and added many more layers - some with similar data 
density. No matter what your cartographic viewpoint on these issues 
are I can attest that maps with as many as 25 layers and as many as 
50 classes per layer can be assembled and used without any confusion 
on the part of the user. With thousands of users, ranging from top 
professionals to rank amateurs, we have never had a complaint of 
confusing presentation of the data.

There is a price to pay for this complexity. I have spent as much as 
two months, full time, styling some of these maps. I bring skills 
from paper map cartography, graphic arts and advertising that are 
very helpful in visualizing and implementing map styling. Personally 
I feel these skills should be taught as an integral part of a modern 
GIS education.

The keys to producing such complex maps is an understanding of human 
visual and mental perception - the same skills that have always been 
the stock in trade of accomplished cartographers.  Just presenting 
the data by color gradients or stochastic classification will always 
create artificial limits to information density.

There are natural upper limits to visual data density. Those limits 
are more about the skill of the cartographer and the comfort level of 
the user than any hard limits. If it were true that our data had to 
be limited to to 12 visual classes we would never have even 
considered trying to serve an industry where high data density is the 
norm.

The world of cartography did not start when the first map server was 
booted and it is not limited to 600 pixel web maps. If digital 
mapping is to survive and thrive we who drive the development of the 
form need to expand beyond a world view that is limited to a gif 
colorset and coarse visual representations of the real world being 
described. In my view the goal of excellence in mapping can not be 
divorced from the technical aspects of creating those maps.

Just one man's opinion.


>Hello Nico,
>
>I think you have a more fundamental problem here.  I suggest that 50 
>classes are too many for any layer, from a cartographic standpoint. 
>The human eye can only discern so many colors easily.  On top of 
>that, you will probably have background data on your map, which will 
>only add to this cartographic nightmare.
>
>Unfortunately, customers think they want everything, and they don't 
>realize that "more" isn't always better.
>
>My suggestion is to meet with your clients, tell them that 50 
>classes are too many.  Work with them to simplify it to no more than 
>maybe 8-12 classes.  Users will still be able to use the identify 
>and query tools to get the exact attributes of features, if they 
>want to.