Latest Contributions by Mareike_TabeaScheller

‎11-20-2011

Hello, I have a question about the hot spot analysis. I (still) have an island as a study area. So I created a fishnet over the study area and used the Intersect-tool to "cut the edges" to the size of the study area. Then I used the Spatial Join-Tool to see how many point features are in each cell and performed the Hot Spot Analysis. At the edges of the island, I now have cells that are smaller than others. Does this change the result of the Hot Spot Analysis, or does Hot Spot Analysis just calculate within one cell, and the size of the cell does not matter? If I would use the Intersect after performing the Hot Spot Analysis, would I get a right result? Because then, the Hot Spot Analysis was analysing some areas that are not within the study area and where points could not have been located? My results seem to be right, still I want to know whether there is such thing as an edge effect here (maybe the effect is very small?) Thanks for your answers, Mareike

‎10-29-2011

Thank you very much for your answer, Lauren. It is right, that I have a very complicated study area, because it is the polygon of the whole island, so that explains the problems with the confidence envelope! That´s good to know. The points reflect bird sightings. As you suggested, it might be the reason why Ripley´s K shows strange results?! I used the Spatial Autocorrelation tool also to analyse the clustered areas. The results from this tool where right, I suppose, but the Ripleys K-Function showed completely different results. So I used Spatial Autocorrelation in my report in the end. I think I first had some problems with the projection/transformation because I had two coordinate systems in the ArcMap Document, ISN1993 and ISN2004. Thanks for your help, Mareike

‎10-10-2011

Hi! Thanks for your answer. Here is my graph. I noticed if I switch the Boundary Correction Method (I used "Simulate Outer Boundaries") off, the confidence envelope follows the observed line, which is of course also wrong. If I want to use the other two methods I get an error. So I'm still confused.. Mareike

‎09-20-2011

I'm working in Iceland, so I use the ISN_2004 Projected Coordinate System. In the results window of the K-function, it always shows that the tool used NAD_1927_to_NAD_1983_NADCON in the field "Geographic transformations". This just appears automatically. Could this be the "Error" here? What are these geographic transformations for and what kind of transformation should I use? I would be really really glad if someone had a suggestion! :confused:

‎09-15-2011

Hello! I'm working for the first time with the Spatial Statistics tools. I have point data of birds on an island. I want to calculate the K-Function, but the result graph always shows a Confidence Envelope that is under the blue expected line. Why is that? Shouldn't the confidence envelope follow the expected line? I would be glad if anyone had a suggestion what mistake I might have made here. Mareike

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Date Last Visited	‎11-11-2020 02:24 AM

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Latest Contributions by Mareike_TabeaScheller

Hot Spot Analysis Edge Effect?

Re: Ripley's K Confidence Envelope doesn't follow the blue expected line

Re: Ripley's K Confidence Envelope doesn't follow the blue expected line

Re: Ripley's K Confidence Envelope doesn't follow the blue expected line

Ripley's K Confidence Envelope doesn't follow the blue expected line