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  • #6490
    KelGun
    KelGun
    Participant

    I have just this week come across ST-SIM and evaluating whether it will be suitable to use for my project. I am looking to forecast growth in urban extent for 6 cities. I have past urban extents for 1975, 1990, 2000 and 2015 so I know by how many cells my city should grow per year based on past growth. Initially, this will be quite a simple model with just 3 states (high density urban, low density urban and rural) and one transition pathway (urbanisation). However what is crucial in this process are the constraints or ‘zoning’ as referred to by Daniel 2016. In my case it will be waterbodies, slope, protected areas etc. But I also need to portray proximity to roads and rivers as positive drivers. After this I will be doing more in depth LUC modeling so I’m hopeful that ST-Sim can be used for both aspects.

    I have gone through the video tutorials and searched the forum but have not found answers, so hope that you can help.

    My questions are:
    1) how and where do I input the zoning or constraint map? Would this be in the ‘initial conditions – spatial’ as a stratum?
    2) Do all the constraining variables need to be in a single raster?
    3) If roads and rivers are a positive driver would they still be in the zoning raster or a separate one?
    4) In the last video tutorial Leonardo indicates that there will be subsequent tutorials on how to input spatial info (rasters) as original conditions but no such video or information is visible. Is there a resource that I can access for this?
    5) I’ve tried to upload the case study sim files from Daniel 2016 but I get an error about the library not being able to update because there is a “SQL logic error or missing database No such column: Model”. How can I fix this?

    Thanks for your time. I appreciate that providing support for such questions can be tedious but as a user new to this it is invaluable.

    #6500
    Colin Daniel
    Colin Daniel
    Keymaster

    Essentially you can use an advanced feature called spatial multipliers to constrain the transition probabilities over space and time in any way you like. In the limit you can generate one multiplier raster for each transition and timestep. This raster then scales (i.e. multiplies) your base transition probabilities up and down over space and time. So the effect of any spatial layer (i.e. roads, rivers, zoning regulations etc.) can be either positive or negative. You can now also generate these multiplier files dynamically (i.e. as you run your simulation) so that they can be responsive to changes in your landscape. All this is pretty advanced work with our software and really is best done with a scripting language to generate the multiplier files. We recommend R as we have an R package to help but you could also other languages like Python. There are some shortcut ways to generate the spatial multipliers directly in ST-Sim without scripting, as was used in the Daniel et al (2016) paper, however the bottom line is you can do pretty much anything you like in terms of modifying transition probabilities if you are willing and able to venture into R.

    I just tried it and you are right the Daniel et al (2016) supplementary files aren’t working with the latest version of our software. We’ll try to get a fix for this shortly and post it on the forum.

    Note that we have an online course coming up in March that would probably cover a lot of your questions – see http://www.apexrms.com/training. We are actually also updating our videos this week in preparation for another course in February. If you subscribe to our newsfeed on the apexrms.com homepage you’ll get notifications about both the videos and the course.

    #6580
    Colin Daniel
    Colin Daniel
    Keymaster

    More information on how to work with the supplementary files provided with the paper: Daniel et al 2016. Methods Ecol Evol. State-and-transition simulation models – a framework for forecasting landscape change.
    The ST-Sim files associated with this paper can be downloaded from the DRYAD repository at: https://datadryad.org/resource/doi:10.5061/dryad.g58k0/1

    You will need to use SyncroSim version 1.0.13 in order to open the .ssim file associated with this paper. You can access older versions of SyncroSim by navigating part way down the download page on http://www.apexrms.com

    Alternatively, you can download a more recent set of ST-Sim files associated with the paper: Daniel et al 2018. Meth Ecol Evol. Integrating continuous stocks and flows into state-and-transition simulation models of landscape change.
    These files contain the same model as in the previous paper (with some additions for carbon dynamics) and will run with the current version of SyncroSim. You can find these files on DRYAD at: https://datadryad.org/resource/doi:10.5061/dryad.6939c

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