Open Source GIS and Mapping Ideas

Extracting an image chunk from a collection of Large MrSid Images

June 4, 2012 | dylan

Recently needed to extract a small "chunk" from a collection of adjacent MrSid mosaics, each about 4Gb in size. Once again, GDAL came to the rescue, and saved much time and agony wile working with very large, compressed, and proprietary-format files. T... [Read more...]

PostGIS Quickie

November 10, 2011 | dylan

Today I needed to cut out a rectangle of geologic data from a state-wide map in an AEA coordinate system, using a bounding box from a UTM zone 10 region, with the output saved in UTM zone 10 coordinates. PostGIS makes this type of operation very simple... [Read more...]

Soil Series Query for SoilWeb

September 16, 2011 | dylan

A map depicting the spatial distribution of a given soil series can be very useful when working on a new soil survey, updating an old one, or searching for specific soil characteristics. We have recently added a soil series query facility to SoilWeb, w... [Read more...]

Terrain Classification Experiment 2: GRASS, R, and the raster package

May 24, 2011 | dylan

Quick post on terrain classification, based on some trouble folks were having with a previous example on Windows. With the spgrass6 package, raster stacks are created by loading several GRASS files at once: x [Read more...]

First-Cut Approach to Synchronizing Field Notes with GPS Data

May 9, 2011 | dylan

After a week's worth of work in the field, I typically have several pages of hand-written field notes that are associated with GPS waypoints-- badly in need of some kind of transcription/organization. I have yet to find a simple approach for bringing t... [Read more...]

Visualizing Terrain Surface Indicies with Scaled Arrows

April 30, 2011 | dylan

Hamish Bowman recently posted a new GRASS module (d.barb) that can be used to depict the direction and magnitude components of some vector (e.g. wind field) along a raster surface or at points in space. An example (c/o Hamish): read more [Read more...]

Tips for Using our Google Earth Interface to SoilWeb

February 28, 2011 | dylan

GE SoilWeb Demo The folks in Lincoln recently changed the links to the OSDs from http:// to https:// style URLs... which seems to cause problems for new versions of Google Earth. I have noticed that when clicking on soil profile sketches an error is re... [Read more...]

Customizing Maps in R: spplot() and latticeExtra functions

December 15, 2010 | dylan

I recently noticed the new latticeExtra page on R-forge, which contains many very interesting demos of new lattice-related functionality. There are strong opinions about the "best" graphics system in R (base graphics, grid graphics, lattice, ggplot, et... [Read more...]

AQP Examples: Profile Visualization

September 20, 2010 | dylan

Two examples of the output from the profile_plot() function, using data from the Sierra Foothill Region, CA. read more [Read more...]

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...]

GRASS Can Make Pretty Maps

August 23, 2010 | dylan

I have posted a couple examples in the past on the topic of high quality map production from GRASS GIS-- usually via the Generic Mapping Tools. I am not sure why, but I have previously avoided using the traditional cartographic output module that is bu... [Read more...]

Using R and r.mapcalc (GRASS) to Estimate Mean Topographic Curvature

August 3, 2010 | dylan

Recently I was re-reading a paper on predictive soil mapping (Park et al, 2001), and considered testing one of their proposed terrain attributes in GRASS. The attribute, originally described by Blaszczynski (1997), is the distance-weighted mean differe... [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...]

SQLite as an alternative to shapefiles, and some GPS fun in R

May 24, 2010 | dylan

Finally made it out to Folsom Lake for a fine day of sailing and GPS track collecting. Once I was back in the lab, I downloaded the track data with gpsbabel, and was ready to import the data into GRASS. # import GPX from GPS: gpsbabel -t -i garmin -f /dev/... [Read more...]

Accessing Climate Change Data and a Custom Panel Function for Filled Polygons

March 4, 2010 | dylan

GCS Model Grids Recently finished some collaborative work with Vishal, related to visualizing climate change data for the SEI. This project was funded in part by the California Energy Commission, with additional technical support from the Google Earth Team. One of the final products was an interactive, multi-scale Google Earth ... [Read more...]

SoilWeb iPhone App: Beta-Testers?

February 23, 2010 | dylan

iPhone App Screenshot rev 0.2 - icon iphone App Screenshot rev 0.2 - in Fresno More Updates: The application is now available on the Apple iTunes Store. Preliminary documentaion here. read more

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Visual Interpretation of Principal Coordinates (of) Neighbor Matrices (PCNM)

February 21, 2010 | dylan

Principal Coordinates (of) Neighbor Matrices (PCNM) is an interesting algorithm, developed by P. Borcard and P. Legendre at the University of Montreal, for the multi-scale analysis of spatial structure. This algorithm is typically applied to a distance matrix, computed from the coordinates where some environmental data were collected. The resulting "... [Read more...]

Two New Soils-Related KMZ Demos

February 10, 2010 | dylan

LCC KMZ Soil Texture KMZ Forgot to post these KMZ files: 1-km scale, aggregate LCC and soil texture data, derived from SSURGO. These are part of a series of KMZ / raster datasets that will be published soon. See attached files at the bottom of the page. Enjoy! read more

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Interesting use of levelplot() for time series data

January 16, 2010 | dylan

levelplot example: soil temperature (left) and moisture (right) Several recent articles appeared on the R-bloggers feed aggregator that demonstrated an interesting visualization of time series data using color. This style of visualization was readily adapted for the time series data I regularly collect (soil moisture and temperature), and quickly implemented ...

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Estimated Net Worth of SoilWeb- Our Online Soil Survey

December 28, 2009 | dylan

According to the excellent source code evaluation tool, SLOCCount, our online soil survey (SoilWeb) code is worth about $268,543 and would require about 2 years of development time to re-create from scratch with a single developer working full-time. This is a fairly close estimate, as I have been working (part-time) on this ... [Read more...]

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Open Source GIS and Mapping Ideas

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