Posts Tagged ‘tom patterson’

First Look at Natural Earth Vector

Friday, June 12th, 2009

Tom Patterson and I collaborated on the precursor to his first Natural Earth Raster project several years ago and we now preview Natural Earth Raster + Vector, a new free product due Fall 2009 that complements and expands on the previous work by providing detailed GIS linework at the 1:15,000,000 (1:15 million) scale and new versions of the raster product (including cross-blended hyspometric tints). The Washington Post, where I work, is contributing 2 more vector GIS base maps at the 1:50m and 1:110m scales and new versions of Natural Earth Raster will be released for those scales. This is a NACIS and mapgiving co-branded product with assistance from the University of Wisconson-Madison cartography lab, Florida State University, and others.

Please attend the October NACIS 2009 map conference in Sacramento, California for the unveiling.

More description and preview images after the jump.

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Tóth Graphix Blog

Wednesday, March 4th, 2009

Tibor Tóth has been creating shaded relief maps (see examples below) for many years for National Geographic among others and has made himself a little blog talking about some of his projects to make the occasion of his seventy-second birthday.

Post topics include:

Continue reading to Tóth Graphix Blog . . .

Data: ESA Global Land Cover Map Available Online (ESA)

Sunday, January 11th, 2009

ESA’s global land cover map

[Editor’s note: Updated 300 meter resolution global landcover raster provides crisper, better validated snapshot. Available in GeoTIFF format as 1 file or regional (continental-level) compressed files. Thanks Martin!]

Republished from European Space Agency. 
Original post date: 19 December 2008.

View legend. Image previews of the world map (hi-res jpg | tiff). 

ESA’s global land cover map, which is ten times sharper than any previous global satellite map, is now available to the public online from the GlobCover website. It is the highest resolution land cover map that has been completely validated ever released. 

Sixteen experts validated the map using more than 3,000 reference land cover points and showed it had an overall accuracy of 73% weighted by area for its 22 land cover classes. The map’s legend was developed using the United Nation Food and Agriculture Organisation’s (FAO) Land Cover Classification System (LCCS). 

GlobCover legend
  GlobCover legend

The map was generated using 19 months worth of data from Envisat’s Medium Resolution Imaging Spectrometer (MERIS) instrument working in Full Resolution Mode to provide a spatial resolution of 300 m. Data were collected between December 2004 and June 2006.A consortium of specialists worked to process the map, including Medias France, Germany’s Brockmann Consult and Belgium’s Université catholique de Louvain. 

Global validation points
Global validation points
 

These data are useful for many applications, including modelling climate change extent and impacts, conserving biodiversity and managing natural resources. The map has been downloaded by more than 4 000 people since October 2008. 

The GlobCover project is part of ESA’s Earth Observation Data User Element (DUE). An international network of partners has worked with ESA on the project, including the United Nations Environment Programme (UNEP), FAO, the European Commission’s Joint Research Centre (JRC), the European Environmental Agency (EEA), the International Geosphere-Biosphere Programme (IGBP) and the Global Observations of Forest Cover and Global Observations of Land Dynamics (GOFC-GOLD) Implementation Team Project Office.

The GlobCover LC version 2 is available to public through the following ftp server: 
ftp://uranus.esrin.esa.int/pub/globcover_v2/

On the FTP you will find: 
1) The LandCover V2 in greyscale geotiff 
2) The QL – Quality file geotiff 
3) The legend in xls file 
4) The latest Product Description Manual PDM_I2.1

The GlobCover Land Cover product is the highest resolution (300 meters) Global Land Cover product ever produced and independently validated.  The GlobCover Land Cover product is based on ENVISAT MERIS data at full resolution from December 2004 to June 2006.  The GlobCover Land Cover product has been developed in partnership with EEA, FAO, GOFC-GOLD, IGBP, JRC and UNEP.  The GlobCover Land Cover product is labelled according to the UN Land Cover Classification System.

When using the GlobCover Land Cover product acknowledgment shall be as follow: 

Source data: © ESA / ESA GlobCover Project, led by MEDIAS-France 
Image: © ESA / ESA GlobCover Project, led by MEDIAS-France

Natural Earth III – Data for Visualizing Earth from Space (Patterson)

Friday, August 22nd, 2008

[Editor’s note: I am pleased to announce Tom Patterson’s new Natural Earth III. This dataset is optimized for 3d visualization of the earth from space and includes an optimized cloud layer and enhanced colors for broadcast. iPhone and desktop wallpapers are available. Tom will formally present this new dataset at the SoC summer school in Scotland next week. I’m guessing they’ll be a repeat at this year’s NACIS conference as well.. Dig in!]

Republished from ShadedRelief.org.

Natural Earth III is raster map data for creating illustrations and animations of our planet with a plausibly realistic appearance. Using the data requires 3D or mapping software. Legibility is a key feature. Compared to photographs of Earth taken from space, Natural Earth III offers brighter colors, fewer clouds over land areas, distinct environmental zones, 3D mountains, and continuous rivers. Other features include:

  • Interchangeable data files that align precisely with each other.
  • Georeferencing information.
  • Seamless edge matching at 180 degrees longitude.
  • High resolution: 16,200 x 8,100 pixels (80 arc second).
  • Natural Earth III is free and without use restrictions.

Tom Patterson, US National Park Service (Disclaimer)

Data hosted by: Springer Cartographics.

Topology and Projections: 21st Century Cartography

Sunday, June 15th, 2008

maps splash walters gallery baltimore

The traveling map exhibit MAPS: FINDING OUR PLACE IN THE WORLD at the Walter’s in Baltimore, Maryland (via the Field Museum, Chicago) wrapped up last weekend. While looking at John Adam’s Road distance map of England and Wales I was put in mind of how map projections try to preserve several of:

  • Area
  • Distance
  • Shape, and
  • Direction/angle

Then the question arose: Might information (thematic) topology now be interchangable with purely geographical topology?

John Adam’s map from 1680 places towns in relative (not absolute) geographic lat-long coordinates in a rough framework that preserves their orientation to one another and in the rough-shape of their original geography. But the primary purpose of this map is to emphasize the relationship between towns and intra-town distances. Below by Royal Geographic Society.

john adams road map 1680

This topological focus (of NODES and EDGES in math-speak) is perfectly represented in Adam’s map. Circles (nodes) are inscribed with town names and straight lines (edges) connecting town circles are annotated with road distance (not straight-line geographic distance).

Modern scientific cartography, with an emphasis on visualization, might finally be loosening the geographic straight jacket to the point where purely lat-long geography doesn’t matter so much but the inter-connection (edges) of said features (nodes) gains emphases and is preserved.

I believe such thematic topology maps are “geographically” accurate and employ projection just like conventional cartography but these “projections” are as of now ad hoc and not properly defined or formalized and are often created manually. Efficient and effective mathematical formulas should be devised and listed along conventional map projections in publications like Snyder’s (USGS) Map Projections: A Working Manual.

The nearest we come to topologic maps are subway maps and cartograms. More on cartograms below.

new york subway map slice

This subway map of New York City is a topological map where the island area of Manhattan is relatively small geographically but is significantly exaggerated to accommodate the “accurate” display of the topological nodes and edges of subway stations and subway lines. (Dorling cartogram example below by Zach Johnson.)

zach johnson cartogram

Cartograms are a good example of topological maps:

  • Area of symbol represents the NODE weight alone.
  • Distance is based on EDGE weight first and and geographic distance second (trying to approximate the “relatedness” between each, eg close countries close, far countries far).
  • Direction is approximated.
  • Shape is approximated.

Zach Johnson has a good post on this topic on his blog (cartograms are the focus of his Masters Thesis).

Below a New York Times map showing the weighted electoral votes of the 48 contiguous states as the topological area of each state.

ny time cartogram example

Let us examine a map of water flow in a stream network (Kelso and Araya):

six rivers streamflow

One usually sees these maps with a conic projection to preserve equal-land-area. But the river segments are drawn exaggerated to their geographic width to represent the EDGE weight between nodes in the true geography space.

The map is dispensing with equal-land-area between nodes (the overall area and shape are preserved) and instead focusing on DISTANCE and DIRECTION between each node. The edges are “preserved” by exaggerating the stream centerlines to preserve the thematic variable. Overall SHAPE is preserved, but local land AREA is not.

Such topological maps are not diagrams because they are still rooted in land-geography; the placement of the nodes is guided by land geography but shift accordingly to best show the interrelationships between nodes. Ignoring the land-geography by listing the nodes and edges in a chart or table is not a map. A topological map takes a complex n-dimensioned space and represents that topology in a 2d dimensioned space.

precip swiss atlas

Some precipitation maps use “gridded” tightly spaced, regularized nodes and edges (above: Swiss Atlas, 2.0). The “weight” of rain and snow fall is indicated by color. Because of the spacing of the nodes and the hyper-localness of the mapped theme, this “topological map” manages to preserve both the topology and the geography.

nat geo 8th world atlas human chapter opener

The above example from the 8th Edition National Geographic Atlas of the World focuses on the quantity difference between nodes and represents that with height spikes (3d). If this were a topologic projection that needed to show the contents of each node (not the inter-relationship between nodes) the spike height would be flattened out into area alone (2.5d), leading to a grossly exaggerated land-area map but correct population-area cartogram such as:

mworlds_zj.png

Above from the Dutch company Mapping Worlds via Zach Johnson.

tom patterson relief example

Tom Patterson (above) uses this 2.5d term to talk about relief shading of land elevation. But I think it can be used to represent any map that is a representation of more than simply 2 variables (lat and long). Really, much of thematic cartography is 2.5d when it tries to represent complex datasets (like precipitation) with color and other visual variables.

So visualization / modern scientific cartography is focused on examining and preserving / projecting topological relationships. Often these are closely related to geographic space, but not always. That is why I am so fascinated by cartograms :)

How do we measure the “error” and “conformal”-ness in a topological map?

  • Area: Does this “view” of the topology preserve the node and edge weights?
  • Distance: Does this “view” preserve the inter-relations between nodes?
  • Direction: Both topological between nodes and geographically.
  • Shape: Purely geographical. This is what sets some cartograms above others.

For topologic shape:

Projecting a n-dimensioned topology onto a 2d surface has one or more points tangent to the 2d surface. An ideal solution shows all nodes and edges shown flattened out but this would likely require using an interrupted projection with dashed linkage lines between like-lobes content (I have seen this somewhere, need example).

For geographic shape and direction:

We are concerned with local shape (direct neighbors in the topology) and global shape. In the England example above for the Dorling cartogram the north-south direction axis tilts left in the topology. A “best” solution preserves this geographic orientation by rotating the topology network until it “conforms” more to the geography.

Finally, we can visualize this with a modified cartography cube from Zach Johnson:

cart cube zach johnson