Hello, you should provide the code you have tried and report what you expect versus what you get.
But, I imagine the confusion probably comes from having data that is longitude / latitude and wanting a cell size in metres? For that you can use the adjust2longlat argument, which assumes units in kilometres. library(trip) example(trip) ## run example to get a dummy trip object makeGridTopology(tr, cellsize = c(50, 50) / 1000, adjust2longlat = TRUE) Does that help? The trip package is kind of a frozen snapshot from olden times, it should really be updated to use the raster package and make all this stuff far simpler and easier to understand. It used to drive me absolutely crazy trying to specify a grid using the maximally abstract GridTopology function, which is why I wrote "makeGridTopology". The raster package is much better at all of this, but still you have to know a bit about setting the right projection for you data and so on. One day I'll update this, but not many people ask about it - feel free to send suggestions/requests etc. Be aware that the cell size from makeGridTopology is a compromise to approximate a metres-based metric in long/lat - you should really choose a map projection and do analyses in that. Let us know if you want help with that. Cheers, Mike (author of trip). On Sat, Oct 25, 2014 at 7:26 AM, ELODIE CLAIRE MARIE CAMPRASSE <ecamp...@deakin.edu.au> wrote: > G'day everyone, > I am trying to calculate time spent per grid fromages GPS data obtained on > seabirds. I am confused about the MakeGridTopology function of the package > trip. Instead of entering a number of cells with cells.dim, I would like to > enter a distance - ie I want my grid to be of 50 by 50 m. I've tried playing > with cells.dim and cellsize option but I am not managing to get what I need. > Could anyone please clarify how to make such a grid? Cheers heaps! > Elodie > > Sent from my Telstra Next G® device > > _______________________________________________ > AniMov mailing list > AniMov@faunalia.it > http://lists.faunalia.it/cgi-bin/mailman/listinfo/animov > -- Michael Sumner Software and Database Engineer Australian Antarctic Division Hobart, Australia e-mail: mdsum...@gmail.com _______________________________________________ AniMov mailing list AniMov@faunalia.it http://lists.faunalia.it/cgi-bin/mailman/listinfo/animov
