# Select projection extent and resolution

First you need to start a new project within QGIS. Give it a useful name and save your project regularly during the steps in the following sections. Because all calculations in SPHY are metric, you will need to project your data in a metric coordinate system. In the example of the Pungwe basin, we chose the WGS84 UTM Zone 36 South projection (EPSG:32736). Define the minimum and maximum x and y values in the projection that you have chosen that cover the entire area you want to model. Then, define the spatial resolution of your model. The choice of resolution will be a tradeoff of the resolution of your input data, computation resources availability, number of runs you intend to do and required detail for your modelling purpose. For your reference, the model for the Pungwe case study has an extent of 275 x 255 km. For this model the spatial resolution is 1000 x 1000 m, and thus the model contains \~70.000 grid cells. Running this model at a daily time step for 5 years takes about 5 minutes.

In order to create your own model, you need to setup the directory structure. This means you need to create a new SPHY model directory (containing the SPHY model source \*.py files) and in that directory you need to create a new **input** and **output** directory.
