Soil Properties Visualized on a 1km Grid

August 31, 2010 | dylan

Fresno Area Urban Areas vs Irrigated LCC: grey regions are current urban areas A couple of maps generated from a 1km gridded soil property database, derived from SSURGO data where available with holes filled with STATSGO data. Soil properties visualize... [Read more...]

PostGIS in Action Book Review

June 8, 2010 | dylan

I was recently asked to review a soon to be published book on PostGIS, a spatial extension to the very popular Postgresql relational database. I was very excited about receiving an early copy of this book, as the authors have provided countless tips, ... [Read more...]

Getting Parent Material Data out of SSURGO

May 27, 2010 | dylan

  Parent material data is stored within the copm and copmgrp tables. The copm table can be linked to the copmgrp table via the 'copmgrpkey' field, and the copmgrp table can be linked to the component table via the 'cokey' field. The following queries illustrate these table relationships, and show one ... [Read more...]

Estimating Missing Data with aregImpute() {R}

April 19, 2010 | dylan

  Missing Data Soil scientists routinely sample, characterize, and summarize patterns in soil properties in space, with depth, and through time. Invariably, some samples will be lost or sufficient funds required for complete characterization can run out. In these cases the scientist is left with a data table that contains holes (... [Read more...]

Yet Another plyr Example

March 4, 2010 | dylan

another plyr example quantiles (0.05, 0.25, 0.5, 0.75, 0.95) of DSC by temperature bin There are plenty of good examples on how to use functions from the plyr package. Here is one more, demonstrating how to use ddply with a custom function. Note that there are two places where the example function may blow up ...
[Read more...]

Un-Wrapping a Sphere with R

December 8, 2009 | dylan

  Premise I was recently asked to print out a fabric pattern that could be used to cover a sphere, about the size of a ping pong ball, for the purposes of re-creating a favorite cat toy (quite important). Thinking this over, I realized that this was basically a map projection ... [Read more...]

New R-Forge Site for Quantitative Pedology

November 8, 2009 | dylan

Just back from the annual meetings, and it looks like there is a significant interest in collaborative R coding of soils-related algorithms and visualization. A new R-forge site has been created to host Algorithms for Quantitative Pedology. Public release of the 'soil' package should be ready in a couple weeks. ... [Read more...]

Aggregating SSURGO Data in R

September 10, 2009 | dylan

  Premise SSURGO is a digital, high-resolution (1:24,000), soil survey database produced by the USDA-NRCS. It is one of the largest and most complete spatial databases in the world; and is available for nearly the entire USA at no cost. These data are distributed as a combination of geographic and text data, ... [Read more...]

Making Sense of Large Piles of Soils Information: Soil Taxonomy

May 27, 2009 | dylan

Western Fresno Soil Hierarchy: partial view of the hierarchy within the US Soil Taxonomic system   Soil Data Field and lab characterization of soil profile data result in the accumulation of a massive, multivariate and three-dimensional data set. Classification is one approach to making sense of a large collection of this ... [Read more...]

Simple Approach to Converting GRASS DB-backends

May 23, 2009 | dylan

  Premise: The current default database back-end used by the GRASS vector model is DBF (as of GRASS 6.5), however this is probably going to be changed (to SQLite) in GRASS 7. The DBF back-end works OK, however it tends to be very sensitive (i.e. breaks) when reserved words occur in column ... [Read more...]
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