some links

•March 13, 2011 • Leave a Comment — connection between solar explosions and increased risk for earthquakes/tsunamis on vulnerable parts of the earth. — GIS people from across the world converge here to share ideas, projects, and information.

Japan Quake Tsunami map

•March 12, 2011 • Leave a Comment


•March 11, 2011 • Leave a Comment

Arramagong is a self-contained live DVD and Virtual Machine, based on XUbuntu, that allows you to try a wide variety of open source geospatial software without installing anything.

GIS on Reddit

•March 11, 2011 • Leave a Comment

Here are some links to a GIS related subreddit. Can find data, and GIS related topics of discussion inside.

Time Lapse with ArcGIS

•March 8, 2011 • Leave a Comment

Raster – The other GIS data

•March 8, 2011 • Leave a Comment

Azimuth: an angular measurement in a spherical coordinate system.

Example: An azimuth is the measurement of the position of a star in the sky. the star is the point of interest, the reference plane is the horizon of the surface of the sea.

The azimuth is the angle between the north point and the perpendicular projection of the star down onto the horizon.

Euclid: Euclid of Alexandria was a creek mathematician often reffered to as the father of geometry. he was active in alexandria during the reign of ptolemy 1 (322-283 BC)

Euclidean Distance: The distance between the pairs of points in euclidean spaces.

Pythagorean Theory: Pythagoras Theorem is a relation in Euclidean Geometry among the three sides of a right triangle. It states, in any right triangle, the area of the square whose side is the hypotonus (the side opposite the right angle) is equal to the sum of the areas of the squares whose sides are the two legs ( The two sides that meet at a right angle).

Map Algebra: A simple and elegent set based algebra for manuipulating geographic data, proposed by Dr. Dana Tomlin in the early 1980’s.

It is a set of primitive opperations in a GIS which allows two or more raster layers of similar dimensions to produce a new raster layer (map) using algabraic opperations such as addition, subtraction, etc.

Spatial Analysts key functions:

  • Perform overlay analysis including Union, Intersect, and Erase.
  • Perform proximity analysis including Buffer, Near, and Point Distance.
  • Perform surface analysis including Aspect, Hillshade, and Slope.
  • Perform raster processing and conversion.

Spawn campers

•March 8, 2011 • Leave a Comment

“Tim DeChristopher: A Monkey Wrencher comes to Trial”

•February 24, 2011 • Leave a Comment

“A little over two years ago, .. Tim DeChristopher put it all on the line when he entered a federal auction and derailed it so that oil and gas companies could not destroy one of the most beautiful and unique areas on the planet.”

10 Questions (odd numbers)

•February 23, 2011 • Leave a Comment

1. TIN: Triangulated Irregular Network – Represents surface with vector data using irregularly distributed nodes which hold three dimensional coordinates (X,Y, and Z). Nodes are distributed variably based on the Douglas Polgor algorithm which determins which points are most neccessary to an accurate representation of the terrain. “

3. Mass Points: an irregularly distributed mass of points with x,y, and z coordinates used to capture the important variations in the shape of the surface being modeled. “

5. Contiguous data: similar data stored adjacently in cells. (?)

7. Raster: Data that is organized in a grid/matrix with rows and columns to represent thematic data with qualitative value such as land use, soils, streams, and elevation.

9. Zone: A group(zone) of similar data

11. Resolution: Refers to the size and number of screen pixels, typicaly higher resolution is found when the size of pixels decrease, and the number of pixels increase. “

13. Triangulation: The accurate surveying of very large triangles called triangulation networks. “

15. Z-values: The elevation value of a surface at a specific X, and Y coordinate. Also known as Spot Value.

17. Slope: The measurement of how steep the ground surface is. The steeper the surface the greater the slope. Slope is measured by calculating the tangent of the surface. The tangent is calculated by dividing the vertical change in elevation by the horizontal distance. “

19. Elevation: Elevation, is mainly used when referring to points on the Earth’s surface, while altitude is used for points above the surface, such as an aircraft in flight or a spacecraft in orbit, and depth is used for points below the surface. “


•February 16, 2011 • Leave a Comment