Mapshaper is a free and open-source software for spatial data processing. It is written in javascript and runs in your browser without any extra plugins and can perform a range of analysis. It started out as a tool for topologically-aware simplification, but has evolved into a swiss army knife of spatial data processing tools. All processing is done in the browser locally, and I have found that it can handle large volumes of data easily and processing is usually much faster than desktop based GIS software.
Continue readingFind Neighbor Polygons using Summary Aggregate Function in QGIS
Read my previous posts Summary Aggregate and Spatial Filters and Advanced Aggregate Expressions to Automate QA to learn more about the powerful aggregate function.
Continue readingAdvanced Aggregate Expressions to Automate QA in QGIS
This post is the continuation of Summary Aggregate and Spatial Filters in QGIS. I have been exploring aggregate functions more and have found interesting ways to automate tasks in QGIS. One such example is helping automatically keeping track of feature edits to help with Quality Assurance (QA).
Continue readingSummary Aggregate and Spatial Filters in QGIS
QGIS expression engine has a powerful a summary aggregate function that can do spatial joins on the fly. This enables some very interesting uses.
Continue readingApproximating Geodesic Buffers in QGIS
When you want to buffer features that are spread across a large area (such as global layers), there is no suitable projection that can give you accurate results. This is the classic case for needing Geodesic Buffers – where the distances are measured on an ellipsoid or spherical globe. This post explains the basics of geodesic vs. planar buffers well.
Continue readingCreating Animated Flight Lines in QGIS
You may have seen a map where source and destination points are connected via curved lines. It is possible to create such a map in QGIS with a simple trick – using custom projections and densification of lines. I will outline the steps to create such a map.
Continue readingQGIS User Conference 2019
I got a chance to attend the 3rd Annual QGIS User Conference at A Coruña, Spain.
This was the meeting point of over 100 QGIS developers, users, and trainers from all over the globe. It was the first time I met the QGIS community in person, including some of the people whose work I have admired for years. The event took place over 3 days – 2 days of workshops and 1 day of talks. I am putting some of my notes, takeways and links to resources shared on other channels (twitter, telegram, email) for the benefit of folks who were not present
Convert between UTM and Degree coordinates using Google Spreadsheets
Converting between different coordinate reference systems or projection is a fairly standard feature in a GIS. There are a number of command line tools also available for performing bulk-conversions. cs2cs program, part of the PROJ.4 library is my favorite.
Continue readingOpenAQ Workshop Notes
I recently attended the OpenAQ workshop in Delhi . The workshop’s goal was to bring tech, science and media folks working on air quality together and brainstorm how to use open data to tackle air pollution challenges. Below are my notes and links to materials presented during the workshop.
Below are my notes and links to materials presented during the workshop.
Continue readingLine Transact Surveys using OpenDataKit(ODK)
This weekend, I got an opportunity to volunteer with a non-profit called Junglescapes. We took a day trip to the Bandipur forest in Karnataka where they have done extensive work in forest restoration. One of their success stories is working with the locals to remove invasive species such as Lantana from the forest. Junglescapes volunteers and locals carry out regular line transact surveys to determine the impact of their interventions. One of the goals for my participation was to see if we can replace the cumbersone paper forms and handheld GPS devices with a mobile-phone based survey using ODK. I am sharing my notes on how we setup the survey and mapping of the result.
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