All posts by Micha Silver

My Acacia Seedling 2013

A bike trip out to the wadi where a few small acacia seedlings are struggling to survive showed, not surprisingly, that they were pretty dried up. We’ve learned to expect that in our 40+ degree temperatures thru the summer. But I took measurements of the seedling that I’m following, and the results reinforced my optimism:

Acacia Seedling data

Physiological measurements of this tree
located at: Longitude 35d10'18.533"E and Latitude 30d47'33.321"N
Elevation -40 m
Date visited
canopy width (cm.)
height (max)
trunk diameter (cm.)
2/4/201158220.14
28/1/201268300.8
0.7
0.63
23/8/201272350.8
0.76
0.57
17/11/201280380.91
0.75
0.58
16/8/201382510.96
0.88
0.67

I’ll look forward to another visit thru the winter – hopefully after some rainfall – when I expect to see even more growth.

Ancient stones and new bills

Last week the Bank of Israel published drafts of the set of new currency to be put into circulation soon. For this print cycle it was decided to showcase Israeli poets, instead of the usual political figures. What’s more, a stanza from each poet’s work will be printed on the new bills. The four writers that will appear on the 20, 50, 100, and 200 shekel bills include Rachel (Bluwstein) the poet, Shaul Tchernehovsky, Leah Goldberg, and Natan Alterman. Nice touch bringing a wiff of culture into the markets and fast food stands.

Continue reading

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.
Continue reading

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
Continue reading

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 HortonĀ  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.

Continue reading