Python Programming for GIS Data Processing in QGIS

Python is a general purpose programming language that has a strong presence in the GIS industry as many house hold software such as ArcGIS and QGIS do expose their interfaces through python scripting.

Broadly speaking, python can be used for any of the following:-
1~ Scripting and Automation
2~ Web Development
3~ Data Science — including Machine Learning, Deep Learning, Data Analysis, and Data Visualization
4~ Embedded Applications - Hardware Programming
5~ Gaming
6~ Desktop Applications
7~ Network Programming

Here our focus will be to use python to automate GIS processes via well packaged video series as seen below. Python is excellent tool for doing GIS data wrangling, data manipulation and analysis processes. That is exactly what I set out to teach you in this video series.... Let's get our hand dirty manipulating GIS data with python starting with the basics off cause 😊.

Video 1: Getting Started Setting up working environment





Video 2: Writing and executing code





Video 3: How to Install Third-party Python Modules in QGIS 3.x





Video 4: Python Implementations, Comment, Variable, Interactive Help





Video 5: Python Data Types - Part 1





Video 6: Python Data Types - Part 2

Coming soon...
Video 7: Python Data Types - Part 3


Coming soon...

How to Prepare A Site Plan

Before we see "How to a Site Plan can be Prepared", here is a little background to what it is.

Who is a Land Surveyor?
A land surveyor is person who is trained and licensed by a regulatory body to practice legal survey profession in a state. This person will be under the supervision of the state's surveyor general or the director/commissioner of surveys for that state.

One important document produced by land surveyors is the site plan (also called survey plan or professional survey or boundary survey or lot description or final survey or parcel demarcation etc).


What is a Site Plan?
A Site Plan is a graphical description of a parcel of land that is attached to the application of Right of Occupancy (RofO) or Certificate of Occupancy (CofO) over a landed property. It is a necessary legal document required by the authority to approve the development of a land parcel. It is a document that measures the boundary of a parcel of land. It gives an accurate measurement, description of the piece of land.

Information to be Shown on a Site Plan
A professional site plan drawn to scale should show the entire property (including all property lines) with the existing and proposed structures. Other information that must be shown include:
~ the name of the owner of the land surveyed
~ the address or description
~ the size and the drawn-out portion as mapped out on the survey plan document
~ the beacon numbers
~ the name of the Surveyor who drew up the survey plan
~ the date it was drawn and a stamp showing that the land is either free from government acquisition or not
~ the directional arrow (aka North Arrow)
~ the Scale at which the plan was drawn
~ the coordinates system used
~ the reference control beacons used

Why is a Site Plan Required?
The primary reason why a site plan is required is to get what is known as a "Land Information". Before a transaction is consummated over a plot of land, it is always advisable to prepare the site plan presented for the land to basically find out whether it falls under government acquisition or not and as well authenticate the claim of ownership to the land.
In the case of a new construction, building additions, substantial accessory structures, and parking must be submitted on a professional stamped survey. Land authorities will make the final determination whether your project met the requirements to be implemented on that land.

Can I Draw the Site Plan Myself?
Yes, if you have the skills to do it. However, if the purpose of the plan is for legal documentation a registered surveyor most endorses your work to be considered by any authority.

How to Prepare A Site Plan

You don’t have to be a genius to prepare a site plan, but you do have to be able to work with the tools that helps you collect data from site and draw them on a paper.

Basically, there are two phases to producing a site plan namely:-

Phase 1: Site work
Here is where the surveyor goes to the field for the purpose of data collection. Depending on the purpose and the accuracy of the survey plan, different kind of instruments are used for the site data collection. These instruments include:-
a) Chain instrument
b) Compass
c) Theodolite
d) Total station
e) GPS

Whatever the instrument used, you will collect data such as distance, bearings and coordinates that will be used to draw the survey plan in the next phase.

Phase 2: Office Work
This is where you do the actual drawing of the survey plan. There are different kind of instruments used for plotting/charting survey plan, however the most commonly use software is the AutoCAD drafting software.

Learn to draw/plot survey plans using a FREE software similar to AutoCAD from here.

Thank you for reading.

Install Third-party Python Modules in QGIS 3.x on Windows 10 platform

Here is how you can install third-party Python Modules in QGIS 3.x on Windows 10 platform. First let's see one very important module that is not installed with python setup that comes with QGIS. This module we will look at is "Pandas".

If you launch QGIS Python Console, and import 'pandas', you will get error

Steps to solving the problem

Step 1: Search for "OSGeo4W Shell"

Step 2: Right click on it and select "Run a s Administrator"

Step 3: Ensure you can run pip from the command line. You may encounter error that says: No module named pip

In my case I ran python -m ensurepip --default-pip to get pip working. You can learn more from the link above. The "-m" flag import the ensurepip module or package and then run as a script.

Note: If you want to switch the shell from python 2.7 to python 3.x, simply enter this command: py3_env. I will advice you do that because that is what the QGIS 3.x python console is using by default. So, just enter py3_env to switch to python 3 shell, then install your third-party modules there.

Step 4: Run: python -m pip install pandas to get pandas module installed as seen above.
Now you can import and use pandas in QGIS Python Console for further data manipulation without any error as seen below. The "-m" flag import the pip module or package and then run as a script.

That is it!


A video explanation of the steps above is here below:-

How to save High Resolution Image from Google Earth Pro

I have seen many "Google Earth Pro" users taking screenshots of the images instead of saving it directly in high resolution, probably because the "Save Image" function is a little bit obscured. This post will guide you through saving a high resolution image from "Google Earth Pro" released in the year 2018.

At first when you click on the save button, nothing seems to happen aside the "Untitled Map", "Compass", "Scale" and empty "Legend" boxes that pop-up on the screen.

If you look closely, just under the "Untitled Map" box, there appear the "Save Image" tool bar. On that very tool bar, you will see the "Save Image" button. That is the button you actually needed to save the image.

But before you save your image, you will definitely like to update the map title and do other settings. This can be done from the "Map Options" button on the "Save Image" tool bar.

You could also select your preferred image resolution from the tool bar.

Thank you for reading.

An Atlas Map of Nigerian States - QGIS Map Report Tutorial

QGIS 3 comes with a nice feature for creating collection of maps (aka Atlas). This feature is called "Report" in QGIS 3, it works closely like the "Print Layout" (formerly know as "Print Composer" in QGIS 2).

You can access the "Report" window from the project menu as seen below...

In the next few lines, I will demonstrate how to generate a map report in QGIS using the Map of Nigerian States. See the document we want to produce at the end of this tutorial here...

The Difference between the United Kingdom, Great Britain and England

Often people confuse these three: United Kingdom, Great Britain and England. As an example, in sports different names are used for Olympic games different from football World Cup game and many others.

Below is the map of the world and the area in question is this tiny mass of land within the red mark.

Lets zoom in and look at the map closer, the whole of that area is the "British Isles" consisting of five countries which is categorized into to named: Ireland and Great Britain.

Ireland consist of two countries "Republic of Ireland and Northern Ireland", while Great Britain consist of three countries "England, Scotland and Wales".

United Kingdom is made up off the whole of Great Britain and part of Ireland. That is all the countries in Great Britain ("England, Scotland and Wales") are in United Kingdom and in Ireland only Northern Ireland is part, Republic of Ireland isn't part of United Kingdom.

Hmm! This sounds complicated, right? Let clarify this by visualizing it on a map.


British Isles = Ireland + Great Britain

Here purple color for Ireland and blue color for Great Britain to clearly see to two different regions.

Ireland = "Republic of Ireland + Northern Ireland"
Great Britain = "England + Scotland + Wales"

United Kingdom =  "England + Scotland + Wales + Northern Ireland"

I hope that was clear and succinct.
Thank you for reading

Drawing Site Plan with DraftSight a FREE Alternative to AutoCAD

There are many low budget or free Computer-Aided Design (CAD) software alternatives to Autodesk's AutoCAD out there and DraftSight is one of the best alternatives I have used.

Using the free version, you could plot or draw a professional survey plan just as you would do in AutoCAD. In this blog post, I will demonstrate how you will do just that using the free DraftSight CAD software. So, download the DraftSight here and follow the instructions below to activate it.

Instruction 1: Download the software from the link above and launch it to install

Instruction 2: Select Free option and click the next button as seen above.

Instruction 3: Accept the terms in the license agreement and install

The difference between "Geocoding" and "Geolocation"

These two terms are often confused by users in of spatial data. Here is a quick explanation to help clarify the difference between the two. Both of these terms are consistently been misuse by people within the geospatial community.

Address: "Abuja International Conference Centre, Herbert Macaulay Way, Abuja, Nigeria"
Coordinates (in 3D): "Latitude: 9.0438014, Longitude: 7.4919024, Sea level: 503m"

Looking at the landmark address above and its corresponding coordinates in three-dimension (3D), we could say:-

Geocoding - means to 'Convert addresses to geographic coordinates, or the reverse'. While  Geolocation - means to 'Return the precise location of a device based on Wi-Fi or cell towers'.

More elaburate explanation from Wikipedia, the free encyclopedia:-

Geocoding is the computational process of transforming a physical address description to a location on the Earth's surface (spatial representation in numerical coordinates). Reverse geocoding, on the other hand, converts geographic coordinates to a description of a location, usually the name of a place or an addressable location. Geocoding relies on a computer representation of address points, the street / road network, together with postal and administrative boundaries.

Geolocation is the identification or estimation of the real-world geographic location of an object, such as a radar source, mobile phone, or Internet-connected computer terminal. In its simplest form geolocation involves the generation of a set of geographic coordinates and is closely related to the use of positioning systems, but its usefulness is enhanced by the use of these coordinates to determine a meaningful location, such as a street address.

Installed Python Libraries on QGIS Vs Anaconda

As some one who uses Python for Geospatial development, I was tempted to know what modules are installed on QGIS python environment compared to that of Anaconda python.

On the console of the two platforms, I executed this: help('modules') and I got the following out puts.


QGIS:

MetaSearch	console	mkgraticule	sre_parse
PyQt5	contextlib	mmap	ssl
__future__	copy	mmapfile	sspi
_ast	copyreg	mmsystem	sspicon
_asyncio	crypt	mock	stat
_bisect	csv	modulefinder	statistics
_blake2	ctypes	msilib	string
_bootlocale	curses	msvcrt	stringprep
_bz2	cycler	multiprocessing	struct
_codecs	datetime	nbformat	subprocess
_codecs_cn	dateutil	netbios	sunau
_codecs_hk	db_manager	netrc	symbol
_codecs_iso2022	dbi	networkx	symtable
_codecs_jp	dbm	nntplib	sys
_codecs_kr	dde	nose2	sysconfig
_codecs_tw	decimal	nt	tabnanny
_collections	decorator	ntpath	tarfile
_collections_abc	difflib	ntsecuritycon	telnetlib
_compat_pickle	dis	nturl2path	tempfile
_compression	distutils	numbers	textwrap
_csv	doctest	numpy	this
_ctypes	dummy_threading	odbc	threading
_datetime	easy_install	ogr	time
_decimal	email	ogrmerge	timeit
_dummy_thread	encodings	opcode	timer
_elementtree	ensurepip	operator	token
_functools	enum	optparse	tokenize
_hashlib	epsg_tr	os	trace
_heapq	errno	osgeo	traceback
_imp	esri2wkt	osr	tracemalloc
_io	exifread	owslib	traitlets
_json	expressions	parser	tty
_locale	faulthandler	past	turtle
_lsprof	filecmp	pathlib	types
_lzma	fileinput	pbr	typing
_markupbase	fnmatch	pct2rgb	unicodedata
_md5	formatter	pdb	unittest
_msi	fractions	perfmon	urllib
_multibytecodec	ftplib	pickle	urllib3
_multiprocessing	functools	pickletools	uu
_opcode	future	pip	uuid
_operator	gc	pipes	venv
_osx_support	gcps2vec	pkg_resources	warnings
_overlapped	gcps2wld	pkgutil	wave
_pickle	gdal	platform	weakref
_pydecimal	gdal2tiles	plistlib	webbrowser
_pyio	gdal2xyz	plotly	win2kras
_random	gdal_auth	poplib	win32api
_sha1	gdal_calc	posixpath	win32clipboard
_sha256	gdal_edit	pprint	win32com
_sha3	gdal_fillnodata	processing	win32con
_sha512	gdal_merge	profile	win32console
_signal	gdal_pansharpen	pstats	win32cred
_sitebuiltins	gdal_polygonize	psycopg2	win32crypt
_socket	gdal_proximity	pty	win32cryptcon
_sqlite3	gdal_retile	py_compile	win32event
_sre	gdal_sieve	pyclbr	win32evtlog
_ssl	gdalchksum	pydoc	win32evtlogutil
_stat	gdalcompare	pydoc_data	win32file
_string	gdalconst	pyexpat	win32gui
_strptime	gdalident	pygments	win32gui_struct
_struct	gdalimport	pylab	win32help
_symtable	gdalmove	pyodbc	win32inet
_thread	gdalnumeric	pyparsing	win32inetcon
_threading_local	genericpath	pyplugin_installer	win32job
_tracemalloc	getopt	pyproj	win32lz
_warnings	getpass	pythoncom	win32net
_weakref	gettext	pytz	win32netcon
_weakrefset	glob	pywin	win32pdh
_win32sysloader	gnm	pywin32_testutil	win32pdhquery
_winapi	gzip	pywintypes	win32pdhutil
_winxptheme	hashlib	qgis	win32pipe
abc	heapq	queue	win32print
adodbapi	hmac	quopri	win32process
afxres	html	random	win32profile
aifc	http	rasutil	win32ras
antigravity	httplib2	re	win32rcparser
argparse	idna	regcheck	win32security
array	imaplib	regutil	win32service
ast	imghdr	reprlib	win32serviceutil
asynchat	imp	requests	win32timezone
asyncio	importlib	rgb2pct	win32trace
asyncore	inspect	rlcompleter	win32traceutil
atexit	io	runpy	win32transaction
audioop	ipaddress	sched	win32ts
base64	ipython_genutils	scipy	win32ui
bdb	isapi	secrets	win32uiole
binascii	itertools	select	win32verstamp
binhex	jinja2	selectors	win32wnet
bisect	json	servicemanager	winerror
builtins	jsonschema	setuptools	winioctlcon
bz2	jupyter	shapely	winnt
cProfile	jupyter_core	shelve	winperf
calendar	keyword	shlex	winreg
certifi	lib2to3	shutil	winsound
cgi	libfuturize	signal	winxpgui
cgitb	libpasteurize	simplejson	winxptheme
chardet	linecache	sip	wsgiref
chunk	locale	sipconfig	xdrlib
cmath	logging	sipdistutils	xlrd
cmd	lzma	site	xlwt
code	macpath	six	xml
codecs	macurl2path	smtpd	xmlrpc
codeop	mailbox	smtplib	xxsubtype
collections	mailcap	sndhdr	yaml
colorsys	markupsafe	socket	zipapp
commctrl	marshal	socketserver	zipfile
compileall	math	sqlite3	zipimport
concurrent	matplotlib	sre_compile	zlib
configparser	mimetypes	sre_constants

Accessing JSON nested object with python

This blog post highlights the key components to look at when parsing a JSON file with deep level of nested objects and variables.

First thing first, is to load in the file using: with statement...

The nested/child objects can then be accessed like this...
obj1['obj1a']['obj1a_1']['obj1a_2']['obj1a_3']...,
obj2['obj2a']['obj2a_1']['obj2a_2']['obj2a_3']...,
obj3['obj3a']['obj3a_1']['obj3a_2']['obj3a_3']... etc

Take this example, where we have a JSON object with parent object "requests" which contains "0" which also contains "responseCode" which also contains more children (in this case 3 children as seen above). Another child object at the same level with "responseCode" is "testPassFailCounts" which contains 217 more children.

That JSON structure is nested as follow:- requests >> 0 >> responseCode >> ... >> ... >> ... etc. Use a JSON viewer or reader such as JSON Editor Online to visualize the structural arrangement of your specific JSON file.

Now, to access any level of nested child in python follow this code snippet:-

import json

with open('name_of_file.json', encoding='utf-8') as f:
    data = json.load(f)
    
responseCode = data['requests'][0]['responseCode']
testPassFailCounts = data['requests'][0]['testPassFailCounts']

len(responseCode) # will return 3
len(testPassFailCounts) # will return 217

That is it!
Happy coding.