Category Archives: GIS

QGIS fighting bugs

Real bugs, agricultural pests, cause damages to food production throughout the world. GIS techniques can help in monitoring pest infestation by collecting and mapping data from traps, baited with pheromone lures. QGIS when teamed up with Spatialite makes the ideal combination for pest control programs to maintain and display the distribution of different species of insects. Here’s how it’s done. Continue reading QGIS fighting bugs

Geostatistics and rainfall with R

With the rainy winter season behind us, it’s time to summarize how much precipitation we got this year. The southern Negev desert enjoyed above average annual rainfall (in stark contrast to the rest of the country, where we saw only 60% of the multi-year average)

I wrote about creating isohyetal contours some years ago. This time I’ll try to improve my interpolation by using the powerful, open source R statistics program.
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Spatialite helps creating an index of LIDAR tiles

We have a large set of LIDAR data, in separate *.las file, each covering a small rectangular area. I wanted to create a polygon shapefile of the coverage of each tile for reference so I know which files to choose when we need a subset of the whole region. Using a bash “one-liner” and a simple function in Spatialite I had my polygon layer.
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Creating Depth-Volume curves with GRASS-GIS

Our regional Drainage Authority prepared a reservoir at the mouth of a small dry riverbed to catch and regulate flood water coming from a mountain canyon. This reservoir was to act as a buffer to prevent flooding of agricultural fields and residential areas further down the valley. After a sudden rainstorm last week, the reservoir bravely fulfilled (pun intended 😉 ) it’s duty. Now we want to know how much water was actually captured, and to create a depth volume curve for the small “lake” that was formed. Here’s how I did this using GRASS.
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New Labeling in Quantum GIS

The new labeling setup in QGIS has been around for over a year now, and in the upcoming version it will become the default, replacing the old labeling. This new engine brings some advanced options that are quite worth learning, such as bulding labels from expressions, and conditional labeling. I’ll expand on some of these tricks that have already appeared in other QGIS blogs
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Strahler stream order in GRASS

In hydrology, a stream network is composed of segments or “reaches” which are arranged in a hierachy. There are several systems of ordering the stream reaches, the most popular of which is the Strahler or Horton  number. GRASS GIS offers, alongside the watershed delineation tool r.watershed (discussed here), a set of addons for stream network analysis. We’ll examine how to use these addons, and how to use strahler ordering to improve the visual effect of a stream network map.

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