Python is not a difficult language. This is the easiest computer programming language to learn. Here, I’m sharing few resources from where you can learn python even if you are not aware of the basic concepts of programming. This is the resource from where you can easily learn this language from scratch. I learned Python language from Coursera.
At Coursera, you can take following courses to learn python by Dr. Chunk:
Python for everybody (Getting started with Python)
Using Python to Access Web Data
Using Databases with Python
Python Data Structure
For practice, you will get hands on and also chapter-based assignments. I have completed my first course and continued with the second. Spending 4 to 5 hours regularly to learn something new through such courses can give you the best confidence to start working on your project. All the best.
Changing Colours of roads in Map by editing file OSMBright.xml (which is wrong approach)
This is what we have done earlier. Today, we will talk about the right approach to change the colours of the roads, widths of the roads and much more. Now, we will study every concept related to OSM in details, whether it is its database ‘postgresql’ or XML files or any other technology used in this like mapnik, mod_tile, OpenLayers.osm etc. So, we will cover every topic in details and definitely with some good examples. For now, we will start with editing colours of map roads. For this, you need to know about the following-
All the files are stored in the folder OSMBright, address could be /usr/local/share/maps/style/OSMBright/.
So, let’s study each one by one:-
pallette.mss – For style customization like colours and fonts, we can use this file. I wanted to change the colours of primary roads and residential roads, so I made changes in this file and after rendering got the colours of roads of my choice.
roads.mss- This file contains line widths of roads at every zoom level. We can make changes here if we want to change the widths of roads. Also, it uses the colour ids we created in the palette.mss file.
project.mml- This file contains all the information of data stored in the postgresql database. We have given dbname ‘gis’ to our database where details of every line, area and land is stored in file format .mml. This file contains the IDs we used in .mss files to define the properties of roads, buildings etc.
Carto- Carto converts the .mml file into Mapnik XML file. It adds the Carto stylesheet with the every entity.
OSMBright.xml- This is final output mapnik XML file generated with the following command- $ carto project.mml > OSMBright.xml. Now, this file is rendered to show maps on the browser with the attributes of our choice.
Changes I made-
I made some changes in the pallete.mss file to create a map having primary and secondary roads of green colour and all the residential roads with black colour. Also changed building colours to red. Then I recreated the OSMBright.xml file and performed rendering to see the output on the browser. You can see the changes hee in the following screenshots-
If, you want more details, feel free to ask any question and stay tuned for future posts.