Take the 2-minute tour ×
Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. It's 100% free, no registration required.

I have been trying to obtain the following markers effect. How can I do the same in ArcGIS (or any free software)? This image is from a book.alt text

share|improve this question
2  
I took away any "other" free software since I have never heard of Arc as free ;-) –  Nicklas Avén Jan 2 '11 at 9:49

7 Answers 7

up vote 7 down vote accepted

My thought is that this was not done with a point layer but a buffer of a point layer in order to achieve the transparency. I have been working with a layer to reproduce the affect and am not successful with any of the other methods listed in these answers.

I now beleive they are close though. Following instructions to use the graduated symbol and transparency does not ever produce the darker outline for me. When I get the transparency set so it looks like your example the outline doesn't show up as much as your example.

So perhaps a copy of the layer placed above it's parent, and then change so it's transparency is just less than the parent, and the fill is none with an outline of black.

Another method for this would be to use Illustrator an export an AI file or Avenza to access the data directly from Illustrator.

share|improve this answer
    
Thank you very much, the idea of exporting it to an illustrator file really helped me a lot! I had no idea Illustrator could do such changes. Using it has been easier than I expected - although I had no previous experience with it. Thanks. –  relima Jan 8 '11 at 13:04

The symbols shown in the map are standardized proportional symbols. In ArcGIS, I believe under a symbology of a layer there is an option for proportional symbols. The legend arrangement shown here is a nested-legend arrangement. I am not sure if you have space constraint on the map but generally I avoid those because it makes difficult for user to compare symbol. If you do not have space constraint use linear-legend arrangement.

share|improve this answer

Hallo

I guess what you are asking is how to make the symbols grow again with negative numbers.

That should be possible with many softwares. You have one field that defines the colour of the symbol (the (the growing or shrinking population) and then you point to a field with absolute values to define the size of the symbols.

In QGIS it works with the "old" symbology at least. Do like this:
Have your growing shrinking population in percentage in one field, we can call it popchange. then you can create one field with absolute values of the population change. You should also manipulate the range in this field to fit proper symbol sizes. So, if you for instance want symbols from 1 to 20 pixels in size and your maximum value of growing or shrinking population is 300 you do abs(original_percentage)*20/300.

In symbology in QGIS you choose "graduated symbol", create two classes on your field popchange. First class below zero and second above zero. Then you choose your manipulated field for "Drawing by field" "Area Scale" (That part is hidden below the symbols on the right side.)

Sorry for a messy post, but I think you can get the idea from it.

HTH

Nicklas

share|improve this answer

Do this, create two shapefiles of the points, one for negative values, the other for positive. This will prevent overlapping of the points, and you can just size them (absolute value) according to their value, but distinguishing the positive and the negative layers by color. No need to use the multiple attribute nor anything else. By the way i see the legend, the map has two layers with one single title.

share|improve this answer

In ArcGIS I would try the Multiple Attributes option on the Symbology tab in Layer Properties. Here you can press the "Symbol Size" button, where you can set the range and symbolsize manualy. This way you should be able to obtain the wanted marker effect. The transparency is set for the entire layer on the Display tab in Layer Properties.

I hope this helps you.

share|improve this answer

Another option in ArcGIS is the Graduated Symbols option (Layer Properties > Symbology > Quantities). This gives you more control over the number of symbols used and their sizes than the Proportional Symbol. Note that you'd have to use two layers with the same symbol settings, and use a Definition Query or something like that to select out the positive values in one and negative values in the other in order to display them in two different colors. As Steen said, the Transparency is on the Display tab.

share|improve this answer

If you don't want to use Arc's built in proportional symbol, or graduated symbol tools, you can manually calculate this. All you need is a point layer, and a GIS capable of buffering based on a field.

This website provides with the simple math to do it: http://instruct.uwo.ca/geog/242/lab11.htm

Just watch your units. The advantage of this method is you can then create a bivariate symbol by filling the proportional symbol as a choropleth map. The disadvantage is you need to recalculate if your numbers ever change.

The background shaded relief could be easily gotten from Natural Earth if you are working at a global/country scale.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.