Mapping

Show only the Charts, Google Maps, Maps, Photos or Videos.

Home
Topics
Geography
Tree Cover
Tutorials

Questions? Need an updated map? Email me andy@andyarthur.org.

30 Years of Nitrogen Fertilization in Spruce-Fir Forest – CompassLive

"Rocks and sediments bind up almost 98 percent of all nitrogen. The remaining 2 percent is in motion, part of a global chemical cycle that includes humans, bacteria, plants, and the atmosphere.
“Plants need nitrogen to grow,” says U.S. Forest Service research ecologist Steve McNulty. “However, excess nitrogen can harm plants.”

"Nitrogen and sulfur can combine with oxygen to form nitrogen or sulfur oxides. These compounds become part of the atmosphere, where they react with water vapor and other elements. Eventually, the nitrogen and sulfur – now in the form of nitric and sulfuric acid – fall to the ground with the rain drops."

Trading One Bad Map for Another?

"Earlier this month, the social studies classrooms of Boston Public Schools underwent a slight but significant change in decor. Down came the Mercator Projection—a common choice of world maps for schools—which distorts the size of each land mass but keeps continental shapes intact. Up went a different map, the Peters, which stretches out the world in order to give each continent a proportionally accurate amount of room. On the Peters, Canada—so huge on the Mercator—shrinks to its proper size, while Africa, which the Mercator shows shrunk and jammed beneath a too-large Europe, stretches out."

Natural Earth

"Natural Earth is a public domain map dataset available at 1:10m, 1:50m, and 1:110 million scales. Featuring tightly integrated vector and raster data, with Natural Earth you can make a variety of visually pleasing, well-crafted maps with cartography or GIS software."

How does GPS work?

The Global Positioning System (GPS) is a network of about 30 satellites orbiting the Earth at an altitude of 20,000 km. The system was originally developed by the US government for military navigation but now anyone with a GPS device, be it a SatNav, mobile phone or handheld GPS unit, can receive the radio signals that the satellites broadcast.

Wherever you are on the planet, at least four GPS satellites are ‘visible’ at any time. Each one transmits information about its position and the current time at regular intervals. These signals, travelling at the speed of light, are intercepted by your GPS receiver, which calculates how far away each satellite is based on how long it took for the messages to arrive.

Balmville Tree Springs Back To Life.

"Local folklore has it that the tree grew when George Washington planted his walking stick while he and the Continental Army were encamped in nearby Newburgh during the final years of the Revolutionary War but core samples of the tree have dated its growth to 1699, well before American independence. Franklin Roosevelt often came to visit the tree."

The tree was cut down in 2015 when it was in terminal decline and ready to collapse on the road and surrounding houses. This summer though, the energy in the roots have allowed it to spring new branches and come back alive. While not uncommon for a large cut tree to do this, it's still a wonderful story of rebirth.

I often need zero-centered color ramps in QGIS. Here is how to quickly make them:

  1. Open up the Layer Styling Dialog.
  2. Select the column you want to use and number of classes.
  3. Select the color ramp you want to use — typically a two or three color ramp — such as green-white-red or blue-white-red.
  4. Click classify.
  5. Note the highest or lowest value in the classes (such as -152 or 80).
  6. You will want to use the largest absolute value — in this case -152.
  7. Put in the column box, rand(-152, 152) and click classify. If you a using a simple shapefile without many objects, you may have to expand the range slightly, e.g. rand(-200,200), to ensure a full ramp is generated.
  8. Select the column you want to use. Do not click classify.
  9. You will now have a nice, zero centered, balanced color ramp for displaying your data.