KartozaViewing posts for the category FOSSGIS
The Kartoza Intern's journey creating a field survey with QGIS, Mergin and Input
Simple, powerful and efficient field data collection is vital for any project with a geospatial aspect. Input is a FOSS application created by Lutra consulting that brings the power of QGIS to a portable device for data collection. The Kartoza intern team was challenged to get to grips with Input. The team decided to keep it simple and create a project to collect data from local parks, including paths, trees and infrastructure. This blog follows the journey taken by the team and includes tips and tricks to help novice users.
Using geospatial technology to promote Clean Cooking
Access to clean cooking technology (such as gas or electric stoves) can greatly improve health outcomes. Approximately 3 million people depend on biomass fuels such as wood, coal, and dung for cooking to cook with (source: WHO article on household air pollution). The indoor air pollution generated whilst cooking indoors has serious, negative health impacts, with women and children in particular being affected. In fact the World Health Organisation (WHO) notes:
FOSS4G 2019 and QGIS in Bucharest
Open source GIS is alive and well and continues to grow in leaps and bounds around the world. Why so many Government entities in South Africa continue paying a fortune of tax-payers money for privative GIS and database software beats me, when wealthy, developed countries (as in most of Europe, for example) saw the light years ago and enthusiastically embrace FOSS.
Generating an XYZ ASCII file from a QGIS raster
Someone wrote to me asking if it would be possible to generate an XYZ ASCII file from a single band raster layer in QGIS. No doubt there are more efficient ways (this approach is pretty slow but it works), but I thought it would be fun to show how you can iterate over a raster, writing out the value of each cell into a text file (along with the centroid coordinates for that cell).
How to create a QGIS PDF report with a few lines of python
Sometimes you want to automatically generate a report to reflect the latest state of your data. For example you may be capturing spatial data into a PostGIS database and want a snapshot of that every few hours expressed as a pdf report. This example shows you how you can quickly generate a pdf based on a QGIS project (.qgs file) and a QGIS template (.qpt file).
Alternatives to Google Maps Engine
Google will be supporting Google Maps Engine (GME) for only one more year. If your company uses GME or was thinking about it, you'll need to consider alternatives. Kartoza offers various alternatives depending on your use case. We are BoundlessGeo partners and offer support for the OpenGeo Suite in southern Africa. For more details of the Google announcement, including various scenarios where you should consider the OpenGeo Suite, see BoundlessGeo's take on it. Kartoza also offers development, support and training services across other components of the FOSS GIS stack that offer alternatives to Google and other proprietary products - we'd love to hear from you!
A quick hack to select all multipart features in QGIS
Today we wanted to find all the multipart features in this layer:
Orchestrating GeoServer with Docker and Fig
In this article I will detail how to set up a simple orchestrated system of docker containers using:
Setting up a Fedora 21 QGIS Workstation
I have been a long time Ubuntu user (I have actually been using it since Ubuntu 4.10 'Warty Warthog') - the first official release. The advent of Ubuntu saw an end to my distro hopping whilst looking for the 'perfect linux distro'.
Playing with Foreign Data Wrappers in PostgreSQL
Recently I set out to try out the PostgreSQL foreign data wrapper (FDW) because I needed access to data that was in MySQL tables. The main reason I needed to play around was to expose my data to a range of PostgreSQL functions that are better and more recent that MySQL. I also needed to use MySQL data for views and lookups and data-driven styling for some Geoserver layers. FDWs allow remote access to tables or queries from various external third-party databases or file structures.
How to quickly transform a bounding box from one CRS to another using QGIS
Today I needed to convert a bounding box for a tilemill project that I want to bring into QGIS as a tile layer (more on that in a future post if I get it to work...). I needed to convert a bounding box from EPSG:4326 ('Geographic') coordinates to EPSG:3857 (Spherical Mercator). Fortunately it is a fairly trivial process if you don't mind writing a few lines of python in the QGIS python console:
box = QgsRectangle(-19.6875,-37.9962,59.0625,37.4400)
source_crs = QgsCoordinateReferenceSystem(4326)
dest_crs = QgsCoordinateReferenceSystem(3857)
transform = QgsCoordinateTransform(source_crs, dest_crs)
new_box = transform.transformBoundingBox(box)
new_box.toString()
u'-2191602.4749925746582448,-4578889.0142234507948160 : 6574807.4249777207151055,4500615.8633687794208527'