Jump to content

 
Photo

density

- - - - -

  • Please log in to reply
13 replies to this topic

#1
josie

josie

    Master Contributor

  • Validated Member
  • PipPipPipPip
  • 120 posts
  • Gender:Female
  • Location:Netherlands
  • Netherlands

Hi,

I have some coordinate points plotted in arc map (though some are in separate shape files) and I want to show the density of these points in a colourful way. Does anyone know how to do this? I have tried using the density kernel but it doesn't seem to work.

Thanks

josie ;)

#2
Kalai Selvan

Kalai Selvan

    Master Contributor

  • Validated Member
  • PipPipPipPip
  • 159 posts
  • Gender:Male
  • Location:India
  • Interests:Map Making & Map making
  • India

I want to show the density of these points.

I am amazed at your ?, what exactly do you mean by density of colours. Would you help me understand, so that i can help you.

Gisguru

Thanks and Regards
Kalai Selvan


#3
aug_aug

aug_aug

    Key Contributor

  • Validated Member
  • PipPipPip
  • 52 posts
  • Gender:Male
  • Location:Mountlake Terrace, Washington
  • United States

There seems to be a couple of tools in this Arcscript that deal with density, I've never used them for anything so I don't know what they do, but they do reference "density". I think I know what you mean...

http://www.spatialecology.com/htools/

:blink:

#4
James Hines

James Hines

    James Anthony Hines

  • Validated Member
  • PipPipPipPipPipPip
  • 536 posts
  • Gender:Male
  • Location:Centreville, Nova Scotia
  • Interests:Cartography, Philosophy, Politics, Psychology, Economics, Occultism, Spiritualism
  • Canada

I want to show the density of these points.

I am amazed at your ?, what exactly do you mean by density of colours. Would you help me understand, so that i can help you.

Gisguru

He wants to show what ever feature which he doesn't tell us by representing each dot in the density map using colours to represent different values. Manifold has a good example of this in their help file by creating a dot density map displaying different colours of recent tremors in south California.

"There is much beauty that we fail to see through our own eyes teeming with life forms that give us that perception of our reality.  Leaves on the trees blowing gently in the wind, or scarily, the waves pounding through high surf, or lightly on a warm summer’s day; that opportunity to sit or swim in the water on a white beach.   That comfort to shout, “The universal conscious do you hear me?  I am alive, guide me dear logos towards the path of rightnesses.”  Earned what has been kept, no longer to be absorbed into a life filled with cold damn winds and  that stubborn fog clouding  my vision with nothing but darkness."


#5
josie

josie

    Master Contributor

  • Validated Member
  • PipPipPipPip
  • 120 posts
  • Gender:Female
  • Location:Netherlands
  • Netherlands

Well what I have is alot of points which are the location of vessels in the ocean. They are just black points presently. What I want to do is visually show the density of these points, so that the viewer can clearly see areas which are heavily built up with shipping traffic.


Hope that helps

#6
frax

frax

    Hall of Fame

  • Associate Admin
  • PipPipPipPipPipPipPip
  • 2,301 posts
  • Gender:Male
  • Location:Stockholm, Sweden
  • Interests:music, hiking, friends, nature, photography, traveling. and maps!
  • Sweden

Well what I have is alot of points which are the location of vessels in the ocean. They are just black points presently. What I want to do is visually show the density of these points, so that the viewer can clearly see areas which are heavily built up with shipping traffic.


Density per what? Maybe per 1 degree grid cell, normalized to the area of water in that grid cell? (needs to be calculated first).
Hugo Ahlenius
Nordpil - custom maps and GIS
http://nordpil.com/
Twitter

#7
josie

josie

    Master Contributor

  • Validated Member
  • PipPipPipPip
  • 120 posts
  • Gender:Female
  • Location:Netherlands
  • Netherlands

Well what I have is alot of points which are the location of vessels in the ocean. They are just black points presently. What I want to do is visually show the density of these points, so that the viewer can clearly see areas which are heavily built up with shipping traffic.


Density per what? Maybe per 1 degree grid cell, normalized to the area of water in that grid cell? (needs to be calculated first).



Yes, well this is the problem you see. I have no idea how to approach it at all. Like the image below but smaller scale. Previously I used Matlab, basically through trial and error I used an area of 400 by 400m.

http://www.seaweb.or...lpernetal..jpeg

Sorry for the lack of info but I haven't done this in ArcGIS before.

#8
Hans van der Maarel

Hans van der Maarel

    CartoTalk Editor-in-Chief

  • Admin
  • PipPipPipPipPipPipPip
  • 3,859 posts
  • Gender:Male
  • Location:The Netherlands
  • Interests:Cartography, GIS, history, popular science, music.
  • Netherlands

Generally speaking you could create a grid, then do an overlay of your points on the grid. Count the number of points within a gridcell, then do a choropleth map of those numbers.
Hans van der Maarel - Cartotalk Editor
Red Geographics
Email: hans@redgeographics.com / Twitter: @redgeographics

#9
frax

frax

    Hall of Fame

  • Associate Admin
  • PipPipPipPipPipPipPip
  • 2,301 posts
  • Gender:Male
  • Location:Stockholm, Sweden
  • Interests:music, hiking, friends, nature, photography, traveling. and maps!
  • Sweden

Generally speaking you could create a grid, then do an overlay of your points on the grid. Count the number of points within a gridcell, then do a choropleth map of those numbers.


in principle yes, but like I said, you have to normalize for a) not all grid cells are the same size (depending on the projection), and B) not all cells contain the same ratio of water/land (islands, coast). So you have to calculate the area of the grid cell, and the ratio of land/water, to get the sea area per cell - and then you can start to calculate the densities.

Josie - the term of this is often referred to as a "heat map".
Hugo Ahlenius
Nordpil - custom maps and GIS
http://nordpil.com/
Twitter

#10
josie

josie

    Master Contributor

  • Validated Member
  • PipPipPipPip
  • 120 posts
  • Gender:Female
  • Location:Netherlands
  • Netherlands

Thankyou Frax, I managed to make a heat map (this is what I was talking about so thanks) using the desity toolbox. However, I have a couple of data sets, each containing a number of points which I wanted to plot. It doesn't seem to like the larger shp files. It says there is an error when it tries to run it.

#11
josie

josie

    Master Contributor

  • Validated Member
  • PipPipPipPip
  • 120 posts
  • Gender:Female
  • Location:Netherlands
  • Netherlands

by 'desity' i mean 'density' :)

#12
frax

frax

    Hall of Fame

  • Associate Admin
  • PipPipPipPipPipPipPip
  • 2,301 posts
  • Gender:Male
  • Location:Stockholm, Sweden
  • Interests:music, hiking, friends, nature, photography, traveling. and maps!
  • Sweden

Josie - check that the geometry is ok, and see if it is really related to the size (which I doubt) by experimenting with a smaller area.
Hugo Ahlenius
Nordpil - custom maps and GIS
http://nordpil.com/
Twitter

#13
MapMedia

MapMedia

    Hall of Fame

  • Validated Member
  • PipPipPipPipPipPipPip
  • 1,029 posts
  • Gender:Male
  • Location:Davis, California
  • United States

Make a density surface, such as nearest neighbor. Choose a cell size suitable to your total coverage so the surface appears smooth.
There are other options that might suite special display needs, but this is a quick task and one that can be explained and interpreted easily.
If you have Arcview/Spatial Analyst or ArcMap you are a few clicks away.

#14
josie

josie

    Master Contributor

  • Validated Member
  • PipPipPipPip
  • 120 posts
  • Gender:Female
  • Location:Netherlands
  • Netherlands

Thanks to everyone, I have managed to solve this issue and make a very nice density map using the density tools. I just had to change the search radius to 0.1. Thankyou Frax for the term 'heat map'! That was very helpful too. Anyway I used the kernel density command in the end.

I still have something else to try, in which I will make a new density surface so I will inform how this goes. This is due to the fact that when using the general density tools, ArcGIS makes up for the places where there is nothing, and generalises. However, I need it to have no colour where there is nothing and not graduate. Hope that makes sense, will let you know if I manage it nicely.

Josie




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users

-->