Open Source GIS and Mapping Ideas

Importing and Exporting from/to a Garmin GPS

Submitted by dylan on Fri, 2006-05-05 19:02.

Importing and exporting GRASS vector data from/to GPS unit can be done in many ways.

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Finding pockets of soil between the Pinnacles

Submitted by dylan on Wed, 2006-04-26 06:38.
View of the Pinnacles and pockets of soil
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Visual Comparison of 2 Raster Images

Submitted by dylan on Fri, 2006-03-17 22:47.
Comparison of 2 raster images
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Using ColorBrewer to assist with thematic map color selection

Submitted by dylan on Mon, 2006-02-27 19:26.
RColorBrewer Color Combinations
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Sample location density: visualization examples

Submitted by dylan on Fri, 2006-02-03 03:37.

Depicting the relative density of sampling can be an interesting task, especially when the points are highly clustered and sparse. Three simple operations that can reveal subtle patterns in the spatial distribution of sample points were explored:

  • A voronoi tessellation vector operation performed on the actual sample locations.
  • A pseudo-density raster operation based on a count of cells, within proximity to sample points, and within a given radius.
  • A kernel-smoothed density function, based on a given standard deviation of spatial density.
  • A density estimation performed by the density() function from the Spatstat package in R
Sample Location Density - Voronoi
Voronoi tessellation
Sample Location Density - v.neighbors function
Psudo-density calculation
Sample Location Density - v.kernel function detail
Kernel-smoothed density

Spatial density estimation in RSpatial density estimation in R

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Flow path modeling from LiDAR data: initial problems, and some solutions.

Submitted by dylan on Thu, 2006-02-02 22:32.
Example LiDAR Data - Hillshade
Example LiDAR dataset
Example LiDAR Data - Stream Network
Stream Network Detail

Raw LiDAR data is so detailed that localized flow routing algorithms often fail to produce meaningful results. The terraflow algorithm is one such method that appears to work well on such massive grid objects (Homepage).

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Working with Landsat Data

Submitted by dylan on Thu, 2005-12-29 07:03.
Landsat Example: bands 3, 2, 1

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Vector Operations

Submitted by dylan on Sat, 2005-11-12 01:02.

A nice introduction to the GRASS vector model can be found here.

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Converting GRASS vectors from 2D into 3D: v.drape

Submitted by dylan on Wed, 2005-09-28 23:12.

More often than not geographic data come in a format that is essentially two-dimensional: i.e. raster grids and vector points, lines, and areas with only (x,y) style coordinates.

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GRASS GIS: raster, vector, and imagery analysis

Submitted by dylan on Mon, 2005-09-12 21:52.
GRASS Example Image: Flow Accumulation

Hydrologic Modeling
GRASS Example Image: Surface Curvatures
Surface Curvatures
GRASS Example Image: 3D Visualization of Data
3D Visualization

A geographic information system (GIS) can be useful tool for describing, modeling, and interpreting data with a spatial reference. Unlike commerical GIS software GRASS is free, and its source code is available for review, modification, or updating. Soil scientists interested in using digital soil survey information, or 3D visualization of soils data may find that GRASS will fit their needs. In addition, GRASS contains hundreds of raster-based operations, such as DEM creation, hydrologic modeling, and solar radiation modeling.

If you have a Macintosh, installation of GRASS is quite simple. Please see Lorenzo Moretti's great website with instructions and an installer: here.

If you have a UNIX machine it is possible to install a pre-compiled binary version of GRASS. However, not every source has an updated version. For the latest updates, I would suggest compiling GRASS from source code.

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