How to create density maps?

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5
05-21-2011 02:58 AM
AlanStephenson
New Contributor
Hi
I am trying to create density maps from point data. The data is sightings of animals so would have count and coordinates as the data. I would like to plot the data in 4 categories with in a cell 0.05 degrees. The density should indicate animals per km2 and the 4 categories would be 2, 1, 0.5, 0.1 animals per km2.
I attach a map as an example.
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5 Replies
DanPatterson_Retired
MVP Emeritus
I would project all the data first prior to running all the point density analysis.  Once you are done, use the reclassify tool in the Spatial Analayst toolbox to reclass your data
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AlanStephenson
New Contributor
Hi Dan

Thank you very much for taking the time to reply. I appreciate it. I have tried as you suggested but still get strange results. I am a new convert to Arcmap 9.3 having worked with 3.2 previously. If you would be even more patient perhaps you could explain the steps simply. If you had some time, to have a look for me I could send you the basic data?

Once again many thanks for the help so far.

Alan
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DanPatterson_Retired
MVP Emeritus
are you using point density or kernel density?  What output units did you specify? If none are chosen and you are using projected data (assume meters as unit) then your outputs will be relative to 1 m^2.  When you say the results are strange, what are they?
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AlanStephenson
New Contributor
I have tried using both point and kernal density. As regards the output units I have made the output cell size 0.05 which I assume is the degrees as I want to project the cell size as .05 degrees. I am not too sure what the radius setting should be but have changed it to 5.5 as I would assume that a cell size of .05 degrees would be approximately 5.5 km. Is this correct. I reclassified the data as you suggested but still get a map that does not correlate with the data.
I attach a picture of the map I generated as well as the table and shapefile of the data concerned if you need to look at them.

Thanks
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AlanStephenson
New Contributor
Hi William

Thank you very much for your reply and for taking the time to work with the data. I realise one of the problems I am facing is that the data is limited for this type of mapping but your insight into this has given me something to go on with. I will experiment again and see what I can come up with.
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