14. FAQ (Frequently Asked Questions)¶

Here are common questions that appear throughout the workshop.

General

I have a Mac computer. Can I still participate in the workshop?
Yes, QGIS and UMEP are software independent but some of the tutorials are just for windows users. The tutorial on Lidar processing, section 4.4 is for Windows user only. Otherwise, all other activities is for all OS. Installation of UMEP can be a bit cjallenging on a Mac, but help instructions are included below (see below).

Daily shading

I can see shadow patterns during the sunshine hours which is logical. Is it also possible to get a complete dark profile during nights? Because in the shadow animation I can only see the pictures during the day.(What IF I want to have for the complete day)?
The animation is only for daytime when it comes to using the Shadow casting tool. This is because no data are created at night. You can have a look in the output folder and see the geotiff that are created.
On the 21. Dec there is not really a clear difference between Building Shadows and Building+Veg Shadows as there was on 21. June, is that correct?
Yes. You are in Sweden with very low sun elevations and 4-5 level buildings. That results in no vegetation shadows reaching the ground.

LIDAR processing

I cannot start the FUSION viewer in QGIS. What I have been doing wrong?
One common misstake is that FUSION is not installed on your computer. To use FUSION within QGIS yo first need to install the actual software form http://forsys.sefs.uw.edu/fusion/fusionlatest.html. Then you should install the plugin FUSION for processing and make the settings according to the tutorial instructions.

Software installation - Mac

SuPy couldn’t be installed automatically on my Mac. What should I do?

The recommended version 2020.6.30 seems to have installation issues due to a third-party package that prevents installation. If unfortunately such issue happens, please manually install a development version of SuPy manually following these steps:

Prepare utility functions in QGIS-python console by running the following:

import sys, subprocess, os
from pathlib import Path
import platform

# locate QGIS-python interpreter
def locate_py():
    try:
        # non-Linux
        path_py = os.environ["PYTHONHOME"]
    except Exception:
        # Linux
        path_py = sys.executable

    # convert to Path for eaiser processing
    path_py = Path(path_py)

    # pre-defined paths for python executable
    dict_pybin = {
        "Darwin": path_py / "bin" / "python3",
        "Windows": path_py / "python3.exe",
        "Linux": path_py,
    }

    # python executable
    path_pybin = dict_pybin[platform.system()]

    if path_pybin.exists():
        return path_pybin
    else:
        raise RuntimeError("UMEP cannot locate the Python interpreter used by QGIS!")

# install supy
def install_supy(ver=None):

    str_ver = f"=={ver}" if ver else ""
    try:
        path_pybin = locate_py()
        list_cmd = f"{str(path_pybin)} -m pip install supy{str_ver} -U --user".split()
        list_info = subprocess.check_output(list_cmd, encoding="UTF8").split("\n")
        str_info = list_info[-2].strip()
        str_info = (
            str_info
            if len(str_info) > 0
            else f"supy{str_ver} has already been installed!"
        )
        return str_info
    except Exception:
        raise RuntimeError(f"UMEP couldn't install supy{str_ver}!") from Exception

This code snippet should determine the actual path of Python interpreter QGIS is using.

install a development version of SuPy:

Also in the QGIS-python console, run this:

install_supy(ver='2020.7.8dev0')

restart your QGIS

Note

If this issue persists, please raise an issue in the UMEP repo and let Ting Sun know by @sunt05.

Jupyter notebooks CANNOT be launched? What should I do?
Please check the following in your command line tool (e.g., Terminal on macOS, OSGeo4W prompt on Windows given QGIS installed):

Note

if using OSGeo4W prompt, please run py3_env first to switch to your python3 environment.
1. Check if Jupyter notebook is installed:
python3 -m pip show notebook

if not, please install it:

python3 -m pip install notebook --user --upgrade
1. Jupyter notebook is installed but cannot be properly launched:
try to re-install it:

uninstall it first:

python3 -m pip uninstall notebook -y

then install it:

python3 -m pip install notebook --user --upgrade

Tip

Stuck? the help page is a useful page to start.
Please report workshop manual issues at GitHub Issues. Please go from the page with problem as an automatical link will be inserted. Thanks.