{"id":1016,"date":"2015-05-12T04:47:50","date_gmt":"2015-05-12T04:47:50","guid":{"rendered":"http:\/\/blogs.lincoln.ac.nz\/gis\/?p=1016"},"modified":"2023-05-07T04:11:55","modified_gmt":"2023-05-07T04:11:55","slug":"home-on-the-range","status":"publish","type":"post","link":"https:\/\/blogs.lincoln.ac.nz\/gis\/home-on-the-range\/","title":{"rendered":"Home on the Range"},"content":{"rendered":"

In this post we’ll cover the ins and outs of creating home ranges for animals based on point locations. \u00a0This was mainly written as a tutorial for Ecology students but by all means, feel free to have a go.<\/em><\/p>\n

In animal ecology there’s an important concept around home ranges for animals, which could be thought of as their territory, for lack of a better word.\u00a0 If animal ecologists are lucky to have locational data for their animals of interest, they are also often concerned with identifying this territory and some of the environmental characteristics that go with that territory. \u00a0Home ranges tend to look something like this when plotted on a map:<\/p>\n

\"EndResult\"<\/a><\/p>\n

So here we can see isolpleths (contour lines) that contain 50 and 95% of all the locations.\u00a0 Splitting the home range into 50% and 95% contour lines is important to animal ecologists as it enables the researcher to see activity patterns. For example, within the 50% contour is where the animals was estimated to have spent 50% of its time during the period of interest. We can also see the Landcover Database underneath and also the attribute table from a spatial join that allows us to know how many points occurred in each of the landcovers within the 95% isopleth.\u00a0 Sweet, huh?<\/p>\n

In this post I’ll take you through how home ranges are derived and what you can then do with them.\u00a0 There are some built in tools in ArcGIS that allow us to derive some crude home ranges, but as we’ll see, to do it properly means going outside ArcGIS a bit and working with some other software.\u00a0 I’ll cover what you need and how to install the extra bits.<\/p>\n

In many cases, their data have been collected from GPS (Global Positioning System) collars fitted to the animals.\u00a0 Left to wander freely, the GPS records their positions over time which can then be downloaded for analysis later.\u00a0 Below is an example of this in an Excel spreadsheet:<\/p>\n

\"SpreadSheetwithGPS2\"<\/a><\/p>\n

(click here<\/a> for a copy of this speadsheet.<\/p>\n

The first column is an identifier for the individual.\u00a0 In this case, each record relates to the location of a Wapiti known as Edith.<\/p>\n

\"wapiti\"<\/a><\/p>\n

(That isn’t Edith as far as I know – unless females are now growing antlers.\u00a0 Kids these days…)<\/p>\n

From a GIS point of view, the important columns are the Latitude and Longitude ones – these are the x- and y-coordinates that will allow us to map their locations.\u00a0 This spreadsheet can be added to ArcMap in the usual way (though note than when you add it you need to navigate down to the individual sheet, here it’s called ‘Edit 2$’) – here it is shown in my Table of Contents (you’ll need to click the List by Source button to see the table):<\/p>\n

\"TOC\"<\/a><\/p>\n

In order to map the points, right-click on the table name and go to “Display X Y Data…” \u00a0and set it up with the field name for the x-coordinate (Longitude) and the field name for the y-coordinate (Latitude).\u00a0 We haven’t got a z-coordinate (elevation) in these data, but if we did we could also set that.<\/p>\n

\"DisplayXY\"<\/a><\/p>\n

When the window first opens, the Coordinate System Description will be blank.\u00a0 We could leave it that way, but a better practice is to set it.\u00a0 We know that these data were collected with a GPS unit and that GPS uses the WGS84 (World Geodetic System 1984) as its coordinate system, so to set it, click the Edit button and wind your way down the path of: Geographic Coordinate Systems > World > WGS84.\u00a0 (If you’re going to use this one a lot, click the “Add to Favorites” (sic) button, \"AddToFavorites\"<\/a>, and it’ll be there for you next time without having to click through all the folders.\u00a0 Once I’ve clicked okay, the points are then mapped:<\/p>\n

\"MappedPoints\"<\/a><\/p>\n

She’s been busy.\u00a0 Note the points are in a new layer called “‘Edith 2$’ Events”\u00a0 An event layer is a temporary layer and to do any substantial analysis we should really save it as a permanent file.\u00a0 Even better, we should convert it (project it) from Latitude\/Longitude (which is really a 3 dimensional coordinate system) to a 2D flat map projection, which will make area and distance measurements easier and more accurate.\u00a0 The standard projection for New Zealand is New Zealand Transverse Mercator<\/a> (NZTM), a projection that was designed to play very nicely with GPS data.\u00a0 So we’ve got a two step process up next: export the events layer to a shapefile and then project that file from WGS84 to NZTM.<\/p>\n